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Bridge Life Cycle Cost
Optimization
Analysis, Evaluation, & Implementation
MOHAMMED ABED EL-FATAH SAFI
Master of Science Thesis
Stockholm, Sweden 2009
ii
KTH Architecture and
the Built Environment
Bridge Life Cycle Cost Optimization
Analysis, Evaluation, & Implementation
MOHAMMED ABED EL-FATAH SAFI
TRITA-BKN. Master Thesis 278
Structural Design and Bridge, 2009
ISSN 1103-4297
ISRN KTH/BKN/EX-278-SE
iv
© Mohammed Abed El-Fattah Safi, 2009
Supervisor: Professor Håkan Sundquist
Co-supervisor: Dr. Hans-Åke Mattsson
Royal Institute of Technology (KTH)
Department of Civil and Architectural Engineering
Division of Structural Design and Bridges
Stockholm, Sweden, 2009
Cover photo: Svinesund bridge between Sweden and Norway - right is Sweden, left is Norway.
i
PREFACE
This master thesis is devoted as a research study within ETSI project. ETSI project is contributed
between three Nordic countries, Sweden, Norway, and Finland. The main goals of the ETSI project
are to develop a Nordic unified methodology and computer program for bridge LCC evaluation.
After thanking God for granting me the strength and the will to fulfill the targets of this research
study, I would like to express my sincere thanks and hopes to my darling home country (The
occupied Palestine/Gaza), my parents, and my family who have instilled in me the drive and
encouragement to complete this work.
I would like to express my sincere appreciation and gratitude to my supervisors, Prof. Håkan
Sundquist & Dr. Hans Åke Mattsson, for their invaluable guidance, patience, kindness, and
encouragement throughout the work of my master thesis. It has been great honor to work with them
and to learn from their experience.
I want here to greatly appreciate my previous degree supervisors in Egypt, Prof. Baher Abou Stait
& Dr. Ahmed Al-Laithy, for their invaluable guidance and assistants to join KTH.
Finally, I would also like to acknowledge and thank everybody that has contributed to my pleasant
time at KTH during my master studies.
Stockholm, Sweden, Jun 2009
Mohammed Safi
ii
- iii -
ABSTRACT
Decisions related to implementation of a bridge design proposal generally require that several
alternatives be considered. Many factors contribute to an agency’s decision to select a particular
proposal. Although the initial project costs may dominate this decision, initial agency costs,
however, tell only a part of the story.
Currently, almost only functional performance and conventional financial costing guides the design
of a new bridge. A new life cycle framework to integrate all bridge life cycle considerations like the
aesthetical and cultural value, and the environmental impact with the economic issues become very
essential for achieving sustainable infrastructure.
This research study demonstrates a unique methodology and present a new systematic way for
analysis, evaluation, and optimization of the bridge life cycle indicators. This study is presenting a
unique flexible system, integrating all of bridge life cycle issues, and making them measurable and
comparable like the bridge initial cost.
One of the main aims of bridge projects is to preserve the harmony of the scenery and the
surrounding context. Aesthetics is not something that can be added on at the end. For aesthetics to
be successful, it must first be considered as an integral part of the design. Basic bridge aesthetics
design guidelines were proposed, which intended to set down considerations and principles, which
help in eliminating the worst aspects of bridge design and encourage the best.
Based on this unique evaluation system, two computer programs were developed to facilitate the
usage, one for calculating the bridge user cost and one to evaluate the bridge aesthetical and
cultural value. The application of this integrated model to bridge design highlighted a critical
importance of using the life cycle modeling in order to enhance the sustainability of bridge
infrastructure systems.
Keywords: life cycle cost analysis, aesthetical and cultural value, user cost, life cycle assessment
- iv -
DENOMINATIONS AND ABBREVIATIONS
LCC Life cycle cost
LCCA Life cycle cost analysis
LCA Life cycle assessment
SRA Swedish Road Administration
Finnra Finnish Road Administration
BMS Bridge Management System
BaTMan Bridge and Tunnel Management System (SRA’s BMS since 2004)
C
AG
Corresponding Agency cost
C
USER
Corresponding User cost
C
RACV
Corresponding Relative Aesthetical and Cultural Value cost
C
REI
Corresponding Relative Environmental Impact cost
k
AES
Aesthetical and cultural coefficient
k
EI
Environmental impact coefficient
C
REI
Corresponding Relative Environmental Impact cost
T Travel time delay for one vehicle in case of work zone
ADT
t
Average daily traffic at time t
N
t
Number of days needed to perform the work at time t
C
F
Average cost per fatal deaths accident for the society
C
I
Average cost per serious injury accident for the society
w
T
Hourly time value for one truck
w
p
Hourly time value for one passenger care
O
T
Average hourly operating cost for one truck including its goods operation
O
P
Average hourly operating cost for one passenger care
A
n
Bridge accident rates during the normal condition
A
a
Bridge accident rates during the work activities
- v -
CONTENTS
PREFACE v
ABSTRACT v
DENOMINATIONS AND ABBREVIATIONS v
1. INTRODUCTION ................................................................................. 1
1.1 General Background .................................................................................................1
1.2 Objective ....................................................................................................................1
1.3 Definitions..................................................................................................................1
1.4 Terminology...............................................................................................................2
2. AGENCY COST.................................................................................... 4
2.1 Bridge LCC Classification Scheme..........................................................................4
2.2 Costs by the Entity that Bears the Cost (Level 1) ...................................................4
2.2.1 Agency Costs ..........................................................................................................4
2.2.2 User Costs ...............................................................................................................4
2.2.3 Society Costs or Third-Party Costs.........................................................................5
2.3 Costs by LCC Category (Level 2).............................................................................5
2.3.1 Investment Cost (Purchasing, Construction, & Installation) ..................................6
2.3.2 Operation & Maintenance.......................................................................................6
2.3.3 Inspection................................................................................................................7
2.3.4 Repair/Rehabilitation & Replacement ....................................................................8
2.3.5 End of life Management (Demolition and Landscaping) .......................................9
2.4 Costs by Elemental Breakdown (Level 3) ...............................................................9
2.4.1 Elemental Costs ......................................................................................................9
2.4.2 Non-Elemental Costs ............................................................................................10
2.5 Life-Cycle Cost Analysis Approach........................................................................11
2.5.1 Integrated Life-Cycle Cost Analysis Approach....................................................11
2.5.2 Steps in Life-Cycle Cost Analysis ........................................................................12
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2.5.3 Economic Analysis Technique............................................................................. 12
3. BRIDGE USER COST........................................................................ 14
3.1 Introduction............................................................................................................. 14
3.1.1 Definition.............................................................................................................. 14
3.1.2 Background........................................................................................................... 14
3.1.3 Objective............................................................................................................... 14
3.2 Bridge User Cost Components .............................................................................. 15
3.2.1 Traffic Delay Cost (TDC) .................................................................................... 15
3.2.2 Vehicle Operation Cost (VOC) ............................................................................ 16
3.2.3 Accident Cost (AC) .............................................................................................. 17
3.2.4 Failure cost (FC)................................................................................................... 18
3.3 Sources of the Traffic Delay on the Bridge........................................................... 19
3.4 Work Zone and Traffic Flow Condition Relationship ......................................... 19
3.4.1 Work Zone Definition .......................................................................................... 20
3.4.2 Causes of the Traffic Delay at the Work Zone..................................................... 20
3.4.3 Work Zone Construction Window....................................................................... 20
3.4.4 Work Zone & Traffic Flow Conditions................................................................ 21
3.4.5 Work Zone Duration (Nt)..................................................................................... 27
3.5 Traffic Characteristics ............................................................................................ 28
3.5.1 Vehicle Classification........................................................................................... 28
3.5.2 Traffic Growth Rate ............................................................................................. 29
3.5.3 Traffic Control Plan (TCP)................................................................................... 29
3.5.4 Bridge Traffic Capacity........................................................................................ 31
3.6 Developed (BUC) Computer program & Practical Example.............................. 32
3.6.1 Practical Example................................................................................................. 32
3.6.2 Application using the developed computer program............................................ 32
3.6.3 Assumptions Window.......................................................................................... 33
3.6.4 Working Tasks Activation Window..................................................................... 33
3.6.5 Calculation Sheets ................................................................................................ 34
3.6.6 Results Window.................................................................................................... 36
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4. BRIDGE AESTHETICAL AND CULTURAL VALUE ................... 37
4.1 Introduction.............................................................................................................37
4.1.1 Background...........................................................................................................37
4.1.2 Objective...............................................................................................................37
4.2 Issues to be Considered..........................................................................................37
4.2.1 Bridge site classification.......................................................................................38
4.2.2 Cost and aesthetics can be complementary...........................................................38
4.2.3 Corresponding acceptable additional costs...........................................................39
4.3 Bridge Aesthetics Design Guidelines ....................................................................39
4.3.1 Sensitivity of the bridge type to the context and simplicity..................................39
4.3.2 The bridge form as a whole ..................................................................................41
4.3.3 The bridge Parts ....................................................................................................42
4.4 Unique Evaluation System.....................................................................................47
4.4.1 Body of the system................................................................................................47
4.4.2 Numerical values for p
i
and a ...............................................................................48
4.4.3 Bridge site classes.................................................................................................49
4.4.4 Recommended considered evaluation items.........................................................49
4.5 Practical Application and Testing..........................................................................50
4.5.1 The case background.............................................................................................50
4.5.2 The considered design proposals ..........................................................................51
4.5.3 The evaluation process..........................................................................................58
4.6 Developed Computer Program...............................................................................61
4.6.1 Introduction...........................................................................................................62
4.6.2 Working steps description.....................................................................................63
4.6.3 Example ................................................................................................................63
4.6.4 Practical use of the program.................................................................................65
5. BRIDGE ENVIRONMENTAL IMPACT.......................................... 66
5.1 Introduction.............................................................................................................66
5.2 Issued to be Considered..........................................................................................66
5.2.1 Project development stages and considerations....................................................66
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5.2.2 Toxics Classification ............................................................................................ 67
5.2.3 Toxics categories weighting impacts.................................................................... 67
5.2.4 Life cycle assessment (LCA)................................................................................ 68
5.3 Presentation of Previous Studies............................................................................ 68
5.4 Case study................................................................................................................ 70
5.4.1 Total weighted results........................................................................................... 70
5.4.2 Result per bridge and category............................................................................. 71
5.4.3 Impact per m
2
surface area of the bridge.............................................................. 71
6. SUMMARY.......................................................................................... 72
6.1 Conclusion and Discussion.................................................................................... 72
6.2 Recommendation and Further Research .............................................................. 72
BIBLIOGRAPHY.......................................................................................... 73
- 1 -
1. INTRODUCTION
1.1 General Background
Decisions related to implementation of a transportation improvement generally require that several
alternatives be considered. Many factors contribute to an agency’s decision to select a particular
option, although initial project costs may dominate this decision. Initial agency costs, however, tell
only part of the story.
The idea behind this study is that, bridges investment decisions should consider all of the costs and
considerations incurred during the period over which the alternatives are being compared. Bridges
are required to provide service for many years. The ability of a bridge to provide service over time
is predicated on its being maintained appropriately by the agency. Thus the investment decision
should consider not only the initial activity that creates a public good, but also all future activities
that will be required to keep that investment available to the public. It is important to note that the
lowest agency cost option may not necessarily be implemented when other considerations such as
aesthetical and cultural value, user cost, and environmental concerns are taken into account.
1.2 Objective
This study was designed firstly to expose the principles of bridge life cycle cost (BLCC) and
identify all of relevant affected parameters, secondly to separately focus on each life cycle
consideration and deeply illustrate the methodology of assessing its impacts on the whole BLCC.
The most important part of this study is the unique systematic way of converting all of the
theoretical data and parameters to a simple numerical calculations system which is relating the
aesthetical and cultural values, and the environmental impact with the other important aspects of
bridge like functionality, economics and techniques. When doing so, facilitate the implementation
of the optimization process.
The final goal is to create a simple compromise computer program, which is based on these data
and parameters and providing a simple optimization process to help the design makers to chose the
optimum alternative.
1.3 Definitions
Life Cycle Cost (LCC):
Technique which enables comparative cost assessments to be made over a specified period of time,
taking into account all relevant economic factors both in terms of initial capital costs and future
operational costs. In particular, it is an economic assessment considering all projected relevant cost
flows over a period of analysis expressed in monetary value. Where the term uses initial capital
letters it can be defined as the present value of the total cost of an asset over the period of analysis.
Life-Cycle Cost Analysis (LCCA):
LCCA is a cost-centric approach used to select the most cost-effective alternative that accomplishes
a preselected project at a specific level of benefits that is assumed to be equal among project
alternatives being considered. All of the relevant costs that occur throughout the life of an
alternative, not simply the original expenditures, are included.
- 2 -
Benefit-Cost Analysis (BCA):
BCA is the appropriate tool to use when design alternatives will not yield equal benefits, such as
when unlike projects are being compared or when a decision-maker is considering whether or not to
undertake a project. The elements typically included in LCCA and BCA are listed below.
Differences between (LCCA) and (BCA):
The agency that uses LCCA has already decided to undertake a project or improvement and is
seeking to determine the most cost-effective means to accomplish the project’s objectives.
LCCA is appropriately applied only to compare project implementation alternatives that would
yield the same level of service and benefits to the project user at any specific volume of traffic.
Unlike LCCA, BCA considers the benefits of an improvement as well as its costs and therefore can
be used to compare design alternatives that do not yield identical benefits (e.g., bridge replacement
alternatives that vary in the level of traffic they can accommodate), as well as to compare projects
that accomplish different objectives (a road realignment versus a widening project). Moreover,
BCA can be used to determine whether or not a project should be undertaken at all (i.e., whether
the project’s life-cycle benefits will exceed its life-cycle costs).
Life Cycle Assessment (LCA):
Tool for identifying and evaluating the environmental aspects of products and services from the
“cradle to the grave”: from the extraction of resource inputs to the eventual disposal of the product
or its waste. Life Cycle Assessment LCA is for assessing the total environmental impact associated
with a product's manufacture, use and disposal and with all actions in relation to the construction
and use of a building or other constructed facilities. LCA does not address economic or societal
aspects!
1.4 Terminology
Figure 1:1 Bridge breakdown components titles
- 3 -
Table 1:1 Bridge breakdown components name
Superstructure :
The part of structure which
supports traffic (include deck
, slab, and girders)
Deck :
bridge floor directly
carrying traffic loads
Hunching :
Increase in the depth of a continuous beam at the point
of support to withstand the increased moment of
bending on the beam.
Transition pier
Pier separating
different
superstructure types
Substructure
That part of the structure, i.e.
piers and abutments, which
supports the superstructure and
transfers load to the
foundations
Bearing
A component which transmits
forces from that par t to
another part
Abutment
The part of the structure
which supports the
superstructure at its
extremities and retains
earth works.
Pier Cap / Headstock :
A component which transfers
loads from the multiple girders
to the pier.
Safety / throw screen :
protective fence to deter the
launching of objects from the
bridge onto the highway
below
Pedestrian barrier
Traffic barrier :
Parapet – low protective
concrete wall at edge of
bridge deck.
- 4 -
2. AGENCY COST
2.1 Bridge LCC Classification Scheme
There are two primary reasons for establishing a life-cycle cost classification or taxonomy when
evaluating bridges. First, the classification insures that all costs associated with the project are
taken into account. Second, the classification scheme allows for a detailed, consistent breakdown of
the life-cycle cost and net savings estimates at several levels so that a clear picture can be had of the
respective cost differences between material/design alternatives.
The third benefit of this life-cycle cost classification is that, actual construction costs classified by
the same structural elements can be used to compile historical unit cost data on bridge element
costs to be used in future life-cycle cost analyses.
2.2 Costs by the Entity that Bears the Cost (Level 1)
In this level, the costs can be divided as shown in Figure 2:1 below, and will discuss in he
following subsections.
Figure 2:1 Cost by the Entity that Bears the Cost (Level 1)
2.2.1 Agency Costs
Agency costs are all costs incurred by the project’s owner or agent over the study period. These
include but are not limited to design costs, capital costs, insurance, utilities, and servicing and
repair of the facility. Agency costs are relatively easy to estimate for conventional material/designs
since historical data on similar projects reveal these costs, will discuss it later in this chapter.
2.2.2 User Costs
Bridge LCC
Agency cost User Cost Society Cost
Aesthetical &
Cultural Value
Environmental
Impact (LCA)
- 5 -
User costs accrue to the direct users of the project. For example, bridge construction often causes
congestion and long delays for private and commercial traffic. New bridge construction impacts
traffic on the highway over which it passes. Maintenance and repair of an existing bridge, along
with the rerouting of traffic, can impact drivers’ personal time, as well as the operating cost of
vehicles sitting in traffic. Accidents, involving harm to both vehicles and human life, tend to
increase in road work areas; will deeply discuss it later in this chapter (3).
2.2.3 Society Costs or Third-Party Costs
Third-party or spillover costs are all costs incurred by entities who are neither the agency/owners
themselves nor direct users of the project. One example is the lost sales for a business establishment
whose customer access has been impeded by construction of the project, or whose business
property has been lost through the exercise of eminent domain. A second example is cost to humans
and the environment from a construction process that pollutes the water, land, or atmosphere. These
costs can be subdivided into two main categories:
Bridge Aesthetical & Cultural Value (ACV)
Some projects have exceeded all cost estimates but still it has been possible to fulfill them with
success. One of the main aims of bridge projects is to preserve the harmony of the scenery.
Location of a bridge, cultural values of the surroundings, landscape and the viewpoints of local
people have influence on the goals that are set to a bridge in the beginning of a project. Bridges are
often seen more or less as sculptures and icons which the citizens may relate with the soul of the
city. This atmosphere and the will to identify the town and its values with an icon may motivate for
bold and spectacular solutions.
So, absolutely there is a hidden value for the external appearance and the beauty of the bridge, it
should be considered during the design and in the LCCA process. This value is called the ACV.
It is not the intention to provide a formula for good design. Rather it is the intention to set down
considerations and principles, which will help, eliminate the worst aspects of bridge design and
encourage the best, will deeply discuss it later in this chapter (4).
Bridge Environmental Impact (LCA)
Environmental impact categories evaluated include energy and material resource consumption, air
and water pollutant emissions, solid waste generation, energy use, fuel consumption, and emissions
for the traffic. Life cycle assessment is an analytical technique for evaluating the full environmental
burdens and impacts associated with a product system, will deeply discuss it later in this chapter
(5).
2.3 Costs by LCC Category (Level 2)
Level 2 groups the costs according to the life-cycle categories which, in KTH we agreed to classify
them ascending by there occurrence during the bridge life cycle, with these proposed titles as
follow:
Investment Cost (Purchasing, Construction, & Installation)
Operation & Maintenance Cost
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Inspection Cost
Repair/Rehabilitation & Replacement Cost
End of life Management Cost (Demolition and Landscaping)
Historical agency data are only one mechanism that may be used to feed LCCA input needs. The
expert opinion of senior agency staff members can also provide a wealth of information for
investment analyses, as can research conducted by industry and government. Still, the agency will
have to devote resources toward the development and validation of data sources for LCCA inputs,
as well as toward learning how to use those sources.
2.3.1 Investment Cost (Purchasing, Construction, & Installation)
An example of historical agency data for bridge investment costs can be as shown in following
table:
Table 2:1 Investment Feedbacks and Recommendation
2.3.2 Operation & Maintenance
Operation: - The preservation and upkeep of a structure, including all its appurtenances, in its
original condition (or as subsequently improved). Maintenance includes any activity intended to
“maintain” an existing condition or to prevent deterioration. Examples include: cleaning,
lubricating, painting, and application of protective systems.
Maintenance: - The minor repair and preventative maintenance activities necessary to maintain a
satisfactory and efficient structure, usually prescheduled maintenance and repair activities.
An example of historical agency data for bridge operation and maintenance costs can be as shown
in following table:
Table 2:2 Operation & Maintenance Feedbacks and Recommendation
- 7 -
2.3.3 Inspection
The main purpose of the inspections is to ensure that the safety and traffic ability of the bridges
meet the requirements; the inspections reveal the physical and functional condition thus providing
the basis for an efficient and economical bridge management. The bridge inspections in Sweden are
since 1987 divided into three types, according to the nature of their aim, scope and frequency. They
are:
General inspection
Major inspection
Special inspection
General inspection: - The aim of is to follow up the assessed damage during earlier inspections,
detect and assess new damage, and detect if the contracted maintenance work has been properly
performed. Every structural part of the bridge together and their included elements have to be
visually inspected. Structural parts under water are excluded. There is no demand on hand-close
investigation unless new damage is detected. General inspection is a simpler inspection compared
to the major inspection. The scope of the general inspection is to check the recorded damage from
previous major inspections and check if the assessed development of these was correct. If new
damages are detected, they will be recorded and assessed according to current rules. General
inspection has to be performed on bridges with a theoretical span larger than 2,0 meters. Smaller
bridges are normally exempted from this inspection type. The time interval between two general
inspections is maximum three years. The personnel performing this inspection type have to posses
the same competence as the inspectors performing major inspections.
Major inspection: - The most important inspection type performed on the Swedish road bridges.
The scope of this inspection type is to detect and asses damages and defects which can affect the
designed function or the traffic safety, both in the short and the long run (within 10 years). Another
aim is to detect even minor damage or defects that, if not attended to, can cause increased
maintenance or repair costs within a 10-year period. Every structural part and their in-going
elements, which are within hand reach, have to be investigated.
During this inspection, even the structural parts located under the water surface have to be closely
inspected by qualified divers. Even adjoining parts of the bridge such as road embankments, slopes,
abutment ends, fill revetment and fenders have to be inspected. If the inspected bridge contains
mechanical or electrical equipment, such as movable bridges, these parts will also be subject to
close inspection. The inspection has to be done hand-close. Special inspection equipment, such as a
bridge-lift, will allow a close look under the bridge deck, a structural part difficult to inspect
otherwise.
This inspection type requires that a series of physical measurements have to be performed. Such
measurements are made to determine for example the real bottom profile (erosion risk), chloride
content and carbonization of concrete, measurements of the level of corrosion of the reinforcement
bars and cracking. The major inspection has to be carried out at least every sixth year. The demands
on the bridge inspectors performing these are high.
Special inspection: -For more information see BaTMan (2000) or the Swedish Bridge inspection
An example of historical agency data for bridge inspection costs can be as shown in following
table:
- 8 -
Table 2:3 Inspection Feedbacks and Recommendation
2.3.4 Repair/Rehabilitation & Replacement
Repair: - The restoration of a structure, including all its appurtenances, to its original condition (or
as subsequently improved) insofar as practicable. Repair includes any activity intended to correct
the affects of material deterioration by restoring or replacing in-kind any damaged member.
Rehabilitation: - The improvement or betterment of a structure, including all its appurtenances, to
a condition which meets or exceeds current design standards.
Examples of rehabilitation include, widening a bridge to meet lane/shoulder width requirements,
raising a bridge to meet clearance requirements, replacement of substandard bridge rails,
strengthening a bridge to increase load carrying capacity to accepted limits, replacement of deck,
rehabilitation of deck, and rehabilitation of superstructure.
Replacement: - The erection of a new structure at or near an existing structure, with the new
structure(s) intended to receive the service loads from the existing structure which is eventually
abandoned, relocated, or demolished.
An example of historical agency data for bridge repair/rehabilitation & replacement costs can be as
shown in following table:
Table 2:4 Repair/Rehabilitation & Replacement Feedbacks and Recommendation
- 9 -
2.3.5 End of life Management (Demolition and Landscaping)
An example of historical agency data for bridge demolition and landscaping costs can be as shown
in following table:
Table 2:5 Ends of Life Management Feedbacks and Recommendation
2.4 Costs by Elemental Breakdown (Level 3)
The third level of classification organizes costs (1) by specific functional element of the structure or
facility, (2) by activities not assignable to functional elements (e.g., overhead). Parts (2) is the
traditional “elements” cost. We add new-technology introduction costs to measure the unique costs
of using a new material. Schematically Figure 2:2 below will introduce this level.
Figure 2:2 Costs by Elemental Breakdown (Level 3)
2.4.1 Elemental Costs
Elements are major components of the project’s structure, and are sometimes referred to as
component systems or assemblies. Elements common to bridges are superstructure, substructure,
and approach. Each element performs a given function regardless of the materials used, design
specified, or method of construction employed.
Individual cost estimates at the elemental level (e.g., $/square meter to furnish and install a concrete
deck) are most useful in the pre-design stage when a variety of material/design combinations are
being considered. This is the stage at which large net savings can be achieved by making
economically optimal material/design choices as shown in Figure 2:3.
Agency cost
Non-Elemental
Costs
Elemental Costs
Studies,Planning,Design,&
Management
Site Facilitate
Mobilization Camping
Traffic Organization &
Safety Control
Overheads
Introduction of New
Technology
- 10 -
2.4.2 Non-Elemental Costs
Non-elemental costs are all costs that cannot be attributed to specific functional elements of the
project. A common example of a non-elemental agency cost is overhead expenses; a non-elemental
third-party cost could be spillover costs. Because elemental cost categories are useful for generating
and updating historical unit cost measures, all project costs that are not truly elemental must be
excluded from these historical statistics and put in the non-elemental group. Schematically graph
compose these three levels can be as shown in Figure 2:4 below
1
0
0
%
Time
Planning
Design
Construction
Investment decision
Accumulated
consumption of
resources
Possibilities to
influence the final cost
Inauguration
L
C
C
/
C
o
n
s
t
r
u
c
t
i
o
n
c
o
s
t
Operation and
maintenance
Obs change of
time scale
Figure 2:3 Bridge Stages and the possibilities to influence the LCC
- 11 -
Figure 2:4 Bridge LCC Classification Levels
Notation for bridge main structures and its elements are presented in Table 2:6; see also Figure 1:1,
and Table 1:1.
Table 2:6 Bridge Component Breakdown
2.5 Life-Cycle Cost Analysis Approach
2.5.1 Integrated Life-Cycle Cost Analysis Approach
The term life cycle cost (LCC) is not used consistently. The more traditional view of LCC evaluates
costs incurred by government agencies all through the value chain (from raw material acquisition to
end of life). Such costs are termed “agency costs.” Recently, efforts have been made to broaden this
definition to be more inclusive of other costs associated with construction projects. In particular,
several studies, using a more holistic LCC approach, have been conducted with the goal of
determining agency costs as well as user costs
An integrated life cycle assessment, aesthetical and cultural value, and cost model was developed in
this master thesis to evaluate the bridge sustainability, and compare alternative materials and
designs using environmental, economic and social indicators where, the bridge LCC is equal to:
- 12 -
REI RACV USER AG C C C C LCC + + + =
Where:
o C
AG
Is the corresponding Agency cost.
o C
USER
Is the corresponding User cost.
o C
RACV
Is the corresponding Relative Aesthetical and Cultural Value cost.
o C
REI
Is the corresponding Relative Environmental Impact cost.
Where:
Here C
AG
is the Agency cost obtained by cost calculation considering the construction, repair,
maintenance and demolishing costs of the bridge from its whole lifetime.
The Relative Aesthetical and Cultural Value cost C
RACV
of a bridge, is then obtained by equation:
AG C k C AES RACV =
o k
AES
Is the aesthetical and cultural coefficient. Range from +0,30 To -0,30
Finally, the Relative Environmental Impact cost C
REI
of a bridge, is then obtained by equation:
AG REI C k C EI =
o k
EI
Is the environmental impact coefficient. Range from 0,0 To +0,20
Consequently, the system described above enables comparison between different design
proposals, existing bridges and bridge types as well as evaluation of even different construction
methods.
2.5.2 Steps in Life-Cycle Cost Analysis
Define the project objective and minimum performance requirements.
Identify the alternatives for achieving the objective.
Establish the basic assumptions for the analysis.
Identify, estimate, and determine the timing of all relevant costs.
Compute the life-cycle cost of each alternative
Perform sensitivity analysis by reusing different assumptions
Compare the alternatives’ life-cycle costs
Consider other project effects
Select the best alternative.
For LCCA to yield valid results, each project alternative considered must provide the same level of
service or utility for a specific, given volume of traffic. In the event that the alternatives yield
different levels of service or utility, then benefit-cost analysis (BCA), not LCCA, would be the
appropriate decision tool. LCCA provides a comprehensive means to select among two or more
alternatives to accomplish the project.
2.5.3 Economic Analysis Technique
- 13 -
The time value of money is germane to LCCA because costs included in the analysis are incurred at
varying points in time. Figure 2:5 show an example of the bridge LCC cash flow. For LCCA, costs
occasioned at different times must be converted to their value at a common point in time. It's
recommended to use the present value (PV) approach (also known as “present worth”), the formula
to discount future constant value costs to present value is:
( )
n
r
+
× =
1
1
Value Future Value Present
Where:
- r Is the real discount rate
- n Is the number of years in the future when the cost will be incurred.
Figure 2:5 LCC Cash Flow Example
For LCCA to be performed in a right way, the proposals on, how to design the bridge should
contain a lot of documents describing the bridge from a lot of different aspects, Table 2:7 present
these documents as follow.
Table 2:7 Documents to be submit with the bridge design proposal
A) Descriptions B) Design calculations
• General description of the
proposal and
design concept
• Technical description.
• Description of the construction
process.
• Description on how to inspect and
maintain the bridge
• Rough statical and dynamical analyses of
the bridge
• A lot of other important factors that affect
the bridge, as for instance wind, stability,
vibration, stiffness, etc
• Rough estimated cost calculations
• LCC-calculation.
C) Drawings D) Perspective/Photomontage/Model
• Plan.
• Elevation.
• Special elevations in a smaller
scale 1:100.
• Type sections.
• Important details.
• Photomontage of the bridge on four
delivered pictures.
• Model in scale 1:500.
- 14 -
3. BRIDGE USER COST
3.1 Introduction
3.1.1 Definition
Bridge user costs are costs incurred by users of the bridge as a result of deteriorated conditions on
the bridge, such as a narrow width, low load capacity, or low vertical clearance which are resulting
from construction, maintenance, inspection, rehabilitation, and demolition activities, leading to an
increase in the vehicles trip time which is translated into user delay costs, additional vehicle
operating costs and increase risk and accident costs.
3.1.2 Background
The bridges are aging, and the agencies are focusing on maintenance and rehabilitation of existing
bridges infrastructure to a greater extent than ever before. Work on existing bridges, whether its
purpose is to rehabilitate or to add capacity, requires the use of work zones to protect bridge users
and construction workers. By reducing capacity, work zones often cause user costs to rise due to
increases in travel time, vehicle operating costs, and possibly the number and severity of crashes.
User costs contribute significantly to the total life cycle cost and should be considered in the
analysis of bridge networks, designers should consider road user costs when determining the most
appropriate construction staging and final design. A study by the Florida Department of
Transportation (Thompson et al., 1999) estimated that user costs may exceed the repair costs by a
factor of 5 or more.
Bridge user costs are not direct costs, but they do directly affect the public it serves. For example,
the construction of a $1 million full width shoulder to reduce bridge user costs by $2 million
increases agency costs to reduce road user costs.
3.1.3 Objective
This chapter will familiarize the analyst with work zone and traffic characteristics, explain the
possible related bridge user cost components, and provide a step by step procedure for
computations considering all traffic condition related aspects.
Based on this procedures and information, develop a systematic computer program to simplify and
facilitate the quantification and then, enable to determine the cost effectiveness of various
alternatives and optimize the work-zone strategies in order to minimize user costs.
- 15 -
3.2 Bridge User Cost Components
Before addressing bridge user cost calculation procedures, it is helpful to understand the bridge user
cost components. Figure 3:1 illustrate the user cost components and their appearance events.
Figure 3:1 Bridge user cost components and appearance events
Bridge user cost during a work zone are usually evaluated with respect to the traffic delay costs
(TDC), the additional vehicle operating costs (VOC) to cross the work zone, the related-accident-
costs (AC), and the risk of failure cost (FC). The following equation is used to determine bridge
user cost during a work zone.
FC AC VOC TDC Cost User Bridge + + + =
The costs should be calculated to present value and added up for all foreseen maintenance and
repair works for the studied time interval T
E
.
3.2.1 Traffic Delay Cost (TDC)
The traffic delay cost (TDC) results from the increase in travel time through the work zone due to
speed reductions, congestion delays, or increased distance as a result of a detour. Therefore, the
TDC is calculated based on the difference between the time taken to cross the bridge and the time
taken to finish the detour or the work zone.
) 1 (
1
) ) 1 ( (
0
?
=
+
? + × × × =
E
P T T T
T
t
t
t t
r
N ADT T TDC w r w r
Where:-
??? , , = = ? = WZ
o
WZ T
v
L
T T T T o o
- T is the travel time delay for one vehicle in case of work zone, (hour),
- ADT
t
is the average daily traffic at time t, measured in number of, (vehicle/day),
Bridge User Cost
Construction & Installation
Operation & Maintenance
Inspection Repair, Replacement &
Rehabilitation
Traffic Delay Cost Vehicle operation Cost Accident Cost Failure cost
Demolition & landscaping
- 16 -
- N
t
is the number of days needed to perform the work at time t, (Day),
- r
T
is the percentage of trucks from all AVD,
- w
T
is the hourly time value for one truck,
- w
p
is the hourly time value for one passenger care,
- T
WZ
is the time taken to finish the detour or to cross the work zone, (hour),
- T
o
is the taken to cross the bridge during the normal flow conditions, (hour),
- L is the affected bridge length, (km),
- vo is the traffic speed in the normal traffic flow condition, (km/hr),
- v
WZ
is the work zone speed, (km/hr),
- TE is the bridge expected life span.
The duration travel delay time in case of work zone (T) is strongly associated with the traffic flow
condition, the hourly traffic distribution, and work zone construction window; we will do deeply in
this matter in the work zone and traffic characteristics subsection in this chapter.
The value of w
The value of one hour of travel time per vehicle is assumed to be equal to:
o $8/hr/veh regardless of vehicle type; The Federal Highway Administration (1989)
o $25/hr/veh. regardless of vehicle type; He et al. (1997)
o $12/hr/veh. regardless of vehicle type; Schonfeld (2003)
o Thoft-Christensen (2006)
$ 11,38 - 11,58 for passenger cars.
$ 22,31 - 27,23 for trucks
Recommended value of w:
It should be equal to the average hourly wage for average employee in the considered country. The
argument for that is, because W is representing the value of delaying the vehicle driver one hour
instead of reaching his work at time. For example, in Sweden 2009 the average hourly wage is
equal to 120 SEK which is approximately equal to $14, this will be suitable for passenger cars, and
for other vehicles is equal to this value multiply by 2, regardless the number of persons inside the
vehicle, so the recommended value according to Sweden 2009:
$ 14,0 /hr for passenger cars.
$ 28,0/hr for other vehicles.
3.2.2 Vehicle Operation Cost (VOC)
VOC is an additional cost incurred by the bridge user, expressed as extra costs to operate the
vehicle additional time due to the traffic disturbances because of the work zone or detour. The
operating costs include fuel, engine oil, lubrication, maintenance, and depreciation.
) 1 (
1
) ) 1 ( ( OC
0
?
=
+
? + × × × =
E
P T T T
T
t
t
t t
r
O O N ADT T V r r
- 17 -
Where:-
Same parameters are used except for:
- O
T
is the average hourly operating cost for one truck including its goods operation,
- O
P
is the average hourly operating cost for one passenger care.
The value of O
The recommended value according to Sweden 2009:
$ 9,5/hr for passenger cars.
$ 21,5/hr for other vehicles.
3.2.3 Accident Cost (AC)
Background
AC is representing the costs of increasing the risk of crushes, health-care, and deaths which
resulting from the traffic disturbances due to work zone on the bridge.
Although bridge-related accidents represent only about 1.7% of all traffic accidents, the degree of
severity is estimated to be from 2 to 50 times the severity of general roadway traffic accidents. The
average number of peoples were killed in bridge related accidents was determined to be equal to
0.009 persons/accident (Abed-Al-Rahim and Johnston, 1991, 1993).
Computation method
Obviously its consequences appear when comparing two different types bridge structures, where
the risks for accidents and the safe maintainability are differs. The bridge accident costs during
work zone could be calculated as:
[ ]
) 1 (
1
) ( ) ( ) ( C
0
?
=
+
× + × × ? × × =
E
I I F F a n
T
t
t
t t
r
P C P C A A N ADT A
Where:-
Same parameters are used except for:
- A
n
The bridge accident rates during the normal condition, (Accident/Vehicle/L/day),
- A
a
The bridge accident rates during the work activities, (Accident/Vehicle/L/day),
- C
F
The average cost per fatal deaths accident for the society
- C
I
The average cost per serious injury accident for the society
- P
F
The average number of killed persons in bridge related accidents, which is
equal to 0,009 (Persons/Accident)
- P
I
The average number of injured persons (not killed) in bridge related accidents,
which is equal to 0,991 (Persons/Accident)
Value of average cost per accident
- 18 -
[ ] 33 , 1 ) 1 ( ) ( ) ( 783 , 0
05 , 0 033 , 0 073 , 0
? + × × × = WZ BL ADT NOACC
o Swedish Road Administration 2009
$1,500,000 for fatal deaths crush
$500,000 for serious injury crush
o United States of America FHWA
$1,240,000 for fatal deaths crush
$151,000 for serious injury crush
o $68,404 Soares (1999)
o Recommended value in this chapter
$1,500,000 for fatal deaths crush
$160,000 for serious injury crush
Bridge- related accident rate
Aded-Al-Rahim and Johnston (1991, 1993) proposed a model for calculating the risk of accidents
that considers the average daily traffic (ADT) and the bridge length, as follows:
Where:
- NOACC = The number of accidents per year,
- LB = The bridge length in (Feet)
- WZ = The work zone width, in (Feet), equal to zero during normal conditions
Comments & Recommendation
It is difficult to accurately quantify the work zone exposure rate (i.e. the length of the work zone
and the hours and days the work zone queues are in place). Further, the crash rate, while generally
higher in work zones than non-work zones, is still low enough that there may not be any crashes in
a given work zone because the exposure period is just too short to allow for statistically valid
results. Finally, the problem is compounded by the fact that work zones differ in the way they treat
maintenance of traffic. For example, some work zones use permanent barriers, while others use
cones or drums; some narrow the lanes, while others maintain lane width and shoulders, etc.
o While there is a limited amount of work zone crash data, the validity of the data used to
compute the crash rates is sometimes suspected.
3.2.4 Failure cost (FC)
- 19 -
There is a small risk for the total failure of a structure. To get the cost for failure one has to
calculate all costs (KH,j) for the failure, accidents, rebuilding, user delay costs and so on and then
multiply these costs with the probability for failure and with the appropriate present value factor
according to the formula
?
=
+
=
n
j
j
r
R K FC j j H
1
) 1 (
1
,
Rj is the probability for a specified failure coupled to KH,j. For normal bridges the probability of
failure is so small that the failure costs could be omitted in the analysis. The cost for serviceability
limit failure is discussed in Radoji?i? (1999), but actually the methods presented in the present
paper are a kind of statistically LCC-method given that the parameters for remedial actions are
considered random.
o Due to the limited availability of probability of failure data, the inclusion of the failure
costs as part of the Bridge user costs is not recommended.
3.3 Sources of the Traffic Delay on the Bridge
An example of historical agency data and feedbacks including recommended time required to
perform work activates are presented in Table 3:1 as follow:
Table 3:1 Work activities that affect the traffic
3.4 Work Zone and Traffic Flow Condition Relationship
- 20 -
3.4.1 Work Zone Definition
Work zone is defined as an area of a highway in which maintenance and construction operations
are taking place that impinge on the number of lanes available to traffic or affect the operation of
the traffic flowing. Work zones restrict traffic flow either by restraining the capacity of the bridge
or, by posting lower speed limits.
In order to calculate bridge work zone related user costs the characteristics of the work zone must
be defined. Work zone characteristics include such factors as work zone length, number and
capacity of lanes open, duration of lane closures, timing (hours of the day and days of the week) of
lane closures, posted speed, and the availability and traffic characteristics of alternative routes.
3.4.2 Causes of the Traffic Delay at the Work Zone
There are three sources of traffic delay at work zone:
o Speed reduction delay (moving delay),
o Congestion delay (stopping delay).
o Circuity delay (extra distance moving delay),
Speed-reduction delay: result from vehicles moving more slowly than the normal bridge speed.
Congestion delay: occurs when the hourly traffic volume is greater than the capacity of a work zone
for a significant period of time. In this case a queue forms, the queue decreases only during time
periods when the demand is less than the capacity.
Circuity delay: is a term used to describe the additional mileage that users travel, either voluntarily
or involuntarily, on a detour to avoid a bridge work zone or queue situation. Its usually take place
in the construction and in the major replacement activities when the bridge have to be closed.
3.4.3 Work Zone Construction Window
Bridge repair and rehabilitation window (time of day to do the work) traditionally occur at
nighttime because daytime closures cause unacceptable delays to weekday peak travel. However,
the disadvantage of having nighttime closures is that they may lead to lower work quality, longer
closure time and higher construction and traffic control plan costs. Four construction window
strategies are recommended:
o Nighttime shifts closure, from 7:00PM To 5:00AM,
o Fulltime closure, 24 Hour/Day.
o Weekend closure,
o Weekday closure.
Alternatively, combinations of the four construction windows are used some times.
Hourly traffic distribution
The effective procedure for quantifying speed reduction delay and is to convert the ADT into an
hourly volume, estimate the delay on an hourly basis, and cumulate the hourly delay into a daily
delay. Data related to the ADT and the hourly traffic distribution is often available from the
municipalities. As an illustration, Table 3.2 shows an example of hourly traffic distribution
- 21 -
(USDOT/FHWA, 1998) and provides a distribution factor (% ADT) for each hour of the day for
different highway types. Based on this distribution factor, the hourly traffic can be calculated as:
Hourly Traffic = ADT × Distribution Factor
Table 3:2 Example of Hourly Traffic Distribution (USDOT/FHWA, 1998)
Hour Distribution Factor(%ADT) Hour Distribution Factor(%ADT)
From To Interstate Other From To Interstate Other
0 1 1.70% 0.90% 12 13 5.70% 5.70%
1 2 1.40% 0.50% 13 14 5.90% 5.90%
2 3 1.30% 0.50% 14 15 6.30% 6.60%
3 4 1.30% 0.50% 15 16 6.90% 7.70%
4 5 1.40% 0.90% 16 17 7.20% 8.00%
5 6 2.10% 2.30% 17 18 6.60% 7.40%
6 7 3.70% 4.90% 18 19 5.30% 5.50%
7 8 4.90% 6.20% 19 20 4.40% 4.30%
8 9 4.90% 5.50% 20 21 3.80% 3.60%
9 10 5.20% 5.30% 21 22 3.40% 3.00%
10 11 5.50% 5.40% 22 23 2.90% 2.30%
11 12 5.80% 5.60% 23 24 2.40% 1.50%
3.4.4 Work Zone & Traffic Flow Conditions
The duration of work zone delay time is strongly associated with the traffic flow condition. Three
types of the traffic flow condition:
o Unrestricted flow conditions, where the traffic operates under “Base Case” situation
o Forced flow conditions, where traffic operates under “Queue” situation
o Circuity flow condition, where traffic is forced to utilize a detour
Unrestricted Flow Condition
Where the traffic volume is below the work zone capacity, all traffic that flows through the work
zone, must slow down while traveling through it and then accelerate back to normal operating
speed. The delay time components associated with the unrestricted flow condition are described in
the below figure.
Figure 3:2 The Delay Time Duration In Case of Unrestricted Flow Condition
- 22 -
3 2 1 T , , T T T
V
L
T T T T WZ
o
WZ o o + + = = ? =
Where:-
- T is the travel time delay, (hour),
- T
o
is the required to cross the affected bridge length (L) during the normal flow
conditions, (hour),
- T
1
is the time required to decelerate from the normal speed (V
0
) to the work zone
speed (V
WZ
), (hour),
- T
2
is the time required to cross the work zone driving by the posted work zone
speed (V
WZ
), (hour),
- T
3
is the time required to accelerate back from the work zone speed (V
WZ
), to the
normal speed (V
0
), (hour).
Parameters identification and valuation:
L
1
Is the minimum distance needed to decelerate from V
o
to V
wz
(m)
) ( 245
278 . 0
2 2
0
0 . 1
G f
V V
V t d d L
wz
r dec r
±
?
+ = + =
Where:
- d
r
The perception reaction distance (m)
- d
dec
The minimum deceleration distance (m)
- V
0
,V
wz
The normal speed and work zone speed (km/h)
- t
r
The perception/reaction time(Sec.), average equal to 2,5 sec.
- f The AASHTO stopping friction coefficient (dimensionless), Table 3:3
- G The roadway grade (dimensionless), assume it equal to zero(horizontal bridge)
Table 3.3 Design speed and the corresponding friction coefficient (USDOT/FHWA, 1998)
Design Speed
(km/h)
30 40 50 60 70 80 90 100 110 120
Coefficient of
Skidding Friction(f)
0.4 0.38 0.35 0.33 0.31 0.3 0.3 0.29 0.28 0.28
T
1
Is the time needed to decelerate from V
o
to V
wz
(hr)
) (
. 2
0
1
wz
dec
r
V V
d
t T
+
+ =
L
0
Is the optimum work zone length, which is the suitable length to fit the work
equipments, workers, and the working area itself. Of coarse its depend on the type of the
working activities, the bridge length, and the technology used in the work. But we can say
here, the minimum acceptable safe working length should not be less than 150 m regardless
the bridge length, the recommended length can be obtained from the following table:
- 23 -
Table 3:4 Bridge length and the recommended work zone length
Bridge Length (m) <150 150 - 500 >500
Recommended optimum work zone length L0 (m) 150 200 300
For simplification consider the average length regardless the bridge length is equal to 200 m.
T
2
Is the time required to cross the work zone driving by V
WZ
, (hour),
wz V
L
T
0
2 =
L
3
Is the minimum distance needed to accelerate back from V
wz
to V
0
2
) (
2
3
3 3
T a
T V L wz + =
Where:
- a is an average vehicle acceleration rate which is equal to 2,28 m/Sec
2
(29458,8km/hr)
T
3
Is the time required to accelerate back from V
WZ
to V
0
, (hr).
a
V V
T
wz ?
=
0
3
As an application for the above mentioned system and formulas, we can relate the travel
time delay of the bridge work zone to bridge normal speed as shown in Table 3:5.
Table 3:5 Traffic delay time due to unrestricted flow condition
Forced Flow Condition
Where the traffic volume exceeds the work zone capacity, traffic flow breaks down and a queue of
vehicles develops as shown in Figure 3.4. Once a queue develops, all approaching vehicles must
stop at the approach to the work zone and creep through the length of the physical queue under
forced flow conditions at significantly reduced speeds, it is common for queues to develop in the
- 24 -
morning peak traffic period, dissipate, and then redevelop in the afternoon peak traffic period. The
delay time components associated with the forced flow condition are described in the below figure.
Figure 3:3 The Delay Time Duration In Case of Forced Flow Condition
4 3 2 1 T , , T T T T T
V
L
T T T T q WZ
o
WZ o o + + + + = = ? =
Where:-
- T is the travel time delay, (hour),
- T
o
is the required to cross the affected bridge length (L) during the normal flow
conditions, (hour),
- T
1
is the time required to stop the vehicle from the normal speed (V
0
), (hour),
- T
q
is the time required to creep through the queue by the queue speed (V
q
), (hour),
- T
2
is the time required to creep through the work zone by firs step, accelerating from
The queue speed (V
q
) the work zone speed(V
WZ
), (hour),
- T
3
is the time required to creep through the work zone by second step, driving by
work zone speed(V
WZ
), (hour),
- T
4
is the time required to accelerate back from the work zone speed (V
WZ
), to the
normal speed (V
0
), (hour).
Parameters identification and valuation:
L
1
Is the minimum stopping sight distance needed to decelerate from V
o
to 0 ,
(m)
) ( 245
278 . 0
2
0
0 1
G f
V
V t d d L r b r
±
+ = + =
Where:
- d
r
The perception reaction distance (m)
- d
b
The minimum breaking distance (m)
- V
0
The normal speed, (km/h)
- t
r
The perception/reaction time (Sec.), average equal to 2,5 sec.
- f The AASHTO stopping friction coefficient (dimensionless)
- G The roadway grade (dimensionless), assume it equal to zero(horizontal bridge)
- 25 -
T
1
Is the time needed to stoop the vehicle (Sec.)
0
1
2
V
d
t T
b
r + =
L
q
Is the average length of the queue ,
(m)
(AQV) (AVL) Lq /Lan vehicles queued Average lenght vehicle Average × =
The average vehicle length includes an assumed vehicle length (VL) and the space between
vehicles. The mixed flow VL is 7,62 m. The space between vehicles is computed as one VL for
every 16 km/h of the average queue velocity (V
q
). The minimum average vehicle length is 12,2 m.
¦
)
¦
`
¹
¦
¹
¦
´
¦
+
=
m ,
V
, ,
AVL
q
2 12
)
16
( 62 7 62 7
of max.
V/C Ratio
The volume to capacity (V/C) ratio is calculated by dividing capacity of the bridge in case of work
zone by the normal capacity of the bridge. The average queue velocity (V
q
) is determined by using
V/C Ratio and the following graph.
0
5
10
15
20
25
30
35
40
45
0 0.2 0.4 0.6 0.8 1
V/C Ratio
A
v
e
r
a
g
e
Q
u
e
u
e
V
e
l
o
c
i
t
y
V
q
(
k
m
/
h
r
)
Figure 3:4 Average Queue Velocity Vq versus V/C Ratio sourc
NCHRP133)
The formula for this graph can be utilities in the following equation.
0057 0 48 21 18 19
2
, (V/C) , (V/C) , Vq + + =
According to this, the average vehicle length can be calculated as show in Table 3:6.
- 26 -
Table 3:6 Average vehicle length according to bridge configuration
T
q
Is the time required to creep through the queue (Sec.)
q
q
q
V
L
T =
L
2
Is the minimum distance needed to accelerate from speed equal to V
q
to V
WZ
2
) (
2
2
2 2
T a
T V L q + =
T
2
Is the time required to accelerate from V
q
to V
WZ
through the work zone, (hour),
a
V V
T
q wz ?
= 2
Where:
- a is an average vehicle acceleration rate which is equal to 2,28 m/Sec
2
(29458,8km/hr)
L
3
Is the remaining work zone length which is equal to L
o
-L
2
2 0 3 L L L ? =
T
3
Is the time required to creep through the work zone by driving with (V
WZ
), (hour),
wz V
L
T
3
2 =
L
4
Is the minimum distance accelerate back needed to from V
wz
to V
0
2
) (
2
4
4 4
T a
T V L wz + =
Where:
- a is an average vehicle acceleration rate which is equal to 2,28 m/Sec
2
(29458,8km/hr)
- 27 -
T
4
Is the time required to accelerate back from V
WZ
to V
0
,
a
V V
T
wz ?
=
0
4
Cricuity Flow Condition
Circuity is a term used to describe the additional distance that users travel, either voluntarily or
involuntarily, on a detour to avoid a highway work zone or because of the bridge closing situations.
For non-detour cases, it is assumed the traffic will remain on the bridge and travel the queue and/or
work zone situations. If a formal detour is established and traffic is forced to detour, the associated
cost components are described below.
D
D
D
o
WZ
V
L
T
V
L
T T T T o o = = ? = , ,
Where:-
- T is the travel time delay, (hour),
- T
o
is the time required to cross the affected bridge length (L) during the normal
flow conditions, (hour),
- L
D
is the length of the detour, (km),
- V
D
is the posted detour speed, (km/hr).
If the traffic is forced to detour and the length of the detour is not mentioned as in the
construction and demolition stages, assume the length of the detour and the detour velocity are
equal to:
Lenght The Bridge LD × = 3
0 85 , 0 V VD × =
3.4.5 Work Zone Duration (Nt)
The duration of the maintenance/rehabilitation activity is a major factor in determining the number
of days a work zone is required. The work zone duration is defined as the length of time a work
activity occupies a specific location. The manual of uniform traffic control devices (MUTCD)
(USDOT/FHWA, 1998) divides work duration into the following five categories:
o Long-term: for several days or more
o Intermediate-term: from a minimum of one day up to several days
o Short-term: for no more than 12 hours
o Short-duration: for up to one hour
o Mobile-work: a work zone that moves continuously
Work Zone Velocity (V
wz
)
"The safety of motorists and construction workers is the top priority of the department," said
Transportation Secretary Gene Conti. "Speeding is the number one contributing factor in work zone
crashes and the results of this partnership should remind motorists that it will not be tolerated."
- 28 -
o Road User Cost Manual (NJDOT)
Generally a 10 - 15 mph reduction in the normal speed (V
0
).
o Chen and Schonfeld, 2003,
On average, V
wz
is equal to 50 km/hr work zones V
0
equal to 80 km/hr
o Michigan Vehicle Code, 1974,
Work zone speed is 45 mph maximum unless otherwise posted,
o National Cooperative Research (NCHRP) report 1996, 2006 adopted by AASHTO,
Maximum speed reduction should not exceed 10 mph,
In case of worker existence on the work zone, V
wz
should be less than 45 mph,
o North Carolina Department of Transportation 2008,
Typical speed limit reductions are 10 mph below the existing posted speed limit a
maximum 15 mph speed reduction may be used,
It is strongly recommended that no speed limits below 55 mph be posted on fully
controlled access facilities,
Speed reduction should applies to an area 1/2 mile in length or greater.
o Recommended Values of V
wz
,
Generally a 15 - 25 mph reduction in the normal speed (V
0
).
Table 3:7 Average vehicle length according to bridge configuration
Normal speed V
0
(km/h) 30 40 50 60 70 80 90 100 110 120
Recommended V
wz
(km/h) 25 30 40 50 60 65 75 85 90 95
3.5 Traffic Characteristics
Bridge user costs are directly dependent on the volume and operating characteristics of the traffic
on the bridge. Each construction, maintenance, and rehabilitation activity generally involves some
temporary impact on traffic using the facility. The impact can vary from insignificant for minor
work zone restrictions on low volume facilities to highly significant for major lane closures on high
volume facilities.
The major traffic characteristics of interest for each work zone include such factors as the overall
projected Average Daily Traffic (ADT) volumes, the associated 24-hour hourly traffic distributions,
and the vehicle classification distribution within the traffic stream. Each of the major traffic
characteristics is discussed in the sections that follow.
3.5.1 Vehicle Classification
Bridges users are not a homogeneous group. They include commercial and non-commercial
vehicles ranging from motorcycles and passenger cars through the heaviest trucks. Appendix of the
- 29 -
FHWA Traffic Monitoring Guide, Third Edition (February 1995) includes 13 different vehicle
classifications. These different vehicle types have different operating characteristics and associated
operating costs.
For simplification of vehicle classifications and consistency with available traffic data, it is
recommended to use Passenger Car and Truck classifications only.
The Truck Percent from the ADT (r
T
)
Of course the percentage of the truck on bridges is differing from case to case. Many case studies
were tock place to compute the average percent of trucks on the roads or bridges. The following
information and equation are concluding some.
o Calgary Region External Truck Survey Study 2001:
Average for All Locations 15.3%
o FSOT Florida Traffic Information 2002 :
Average for All Locations range from 7,36% to 11,74%
o Based on analysis of intensive traffic surveying data, the recommended value
40 , 8 0001 , 0 + = ADT rT
Where:
- r
T
is the percentage of trucks from the AVD,
3.5.2 Traffic Growth Rate
Due to factors such as population growth and economic prosperity, the volume of traffic on bridges
increases each year. Johnston et al. (1994) estimated that the traffic growth on interstate highways
is 4.06% and on other highways is 1.94%.
Calvano (2003) stated that in Canada the traffic growth between 2006 and 2011 is estimated to be
1.1%. Based on these values, the current ADT estimate in the present user cost model is given in
the following equation,
m t
t
Year Year
ADT ADT
?
+ × = %) 1 . 1 1 (
Where:-
- ADT
t
is the ADT to be used in the analysis at year t, (Vehicle/Day),
- ADT is the measured average daily traffic, (Vehicle/Day),
- Year
t
is the current year,
- Year
m
is the last year in which the ADT is measured.
3.5.3 Traffic Control Plan (TCP)
The basic concept of a traffic control plan is to permit the contractor to work on a bridge while
maintaining a safe and uniform flow of traffic. TCP are chosen based on the number of bridge lanes
and the type of repair. Table 3:8 and Figure 3:5 illustrate some available bridge TCP.
- 30 -
Table 3:8 Suggested Traffic Control Plans for Bridge Configurations
Direction Lanes Bridge Configuration
Type
Normal Open
TCP Notes
Two-Lane Undivided 1 1 Plan 1 One lane open for traffic in two directions
Two-Lane Divided 1 1 Plan 2 Shoulder used as a lane in the work zone (*)
Four-Lane Undivided 2 1 Plan 3 One lane closed in one direction
Four-Lane Divided 2 1 Plan 3 One lane closed in one direction
Six-Lane Undivided 3 2 Plan 4 One lanes closed in one direction
Six-Lane Divided 3 2 Plan 4 One lanes closed in one direction
Six-Lane Undivided 3 1 Plan 5 Two lanes closed in one direction
Six-Lane Divided 3 1 Plan 5 Two lanes closed in one direction
Multilane >3 ?2 Plan 6 Two lanes closed in each direction
Special Traffic control Planes
Six-Lane Undivided 3 1,5 Plan 7
Two lanes closed in one direction and
one lane in the other direction
Deck full replacement 0 Plan 8 Full bridge closure and complete detour
Figure 3:5 Suggested Bridge Traffic Control Plans (TCP)
(*) in this case, the cost of the temporally shoulder must be added as extra cost
- 31 -
3.5.4 Bridge Traffic Capacity
Bridge traffic capacity is the maximum number of vehicles passing a point on the bridge at
established bridge conditions. In analyzing bridge work zone related user costs, there are two
possible capacities:
o The capacity of the bridge under normal operating conditions,
o The capacity of the bridge when the work zone is in place,
Normal Bridge Traffic Capacity
Normal Capacity is the maximum traffic volume a bridge can handle under normal bridge
conditions. Table 3.9 provides the ideal capacity a facility type can handle. The normal capacity of
the bridge is used during the non-work zone hours when all traffic lanes are open.
Table 3:9 Normal Bridge Traffic Capacity
Bridge Configuration Type Ideal Capacity Veh/lane/hour
Two-Lane Undivided 1,400
Two-Lane Divided 1,400
Four-Lane Undivided 2,100
Four-Lane Divided 2,100
Six-Lane Undivided 2,200
Six-Lane Divided 2,200
Multilane Highway bridge 2,300
Work Zone / Detour Capacity
Bridge capacity in the work zone is estimated from research studies according to intensive traffic
data, and adopted in this chapter according to the traffic control planes Table 3.10 reflects average
vehicle flow capacities at several real world work zones under several lane closure scenarios.
Table 3:10 Bridge Traffic Capacity in Case of Work Zone
Bridge Configuration Type
Traffic Control Plan
(TCP)
Recommended Average Capacity
Veh/lane/hour
Two-Lane Undivided Plan 1 600
Two-Lane Divided Plan 2 900
Four-Lane Undivided Plan 3 1,300
Four-Lane Divided Plan 3 1,300
Six-Lane Undivided Plan 4 1,400
Six-Lane Divided Plan 4 1,400
Six-Lane Undivided Plan 5 1,200
Six-Lane Divided Plan 5 1,200
Multilane Plan 6 1,400
- 32 -
3.6 Developed (BUC) Computer program & Practical Example
As culmination of the progress in this chapter, a simple Excel based computer program was
developed; to illustrate this model let us take a real example during a bridge design competition.
3.6.1 Practical Example
Overview
The project objective is to build, maintain, and eventually dispose of a new interstate bridge. The
engineer first makes a general description of the size of the bridge and the environment in which it
will exist. The structure is 115 meters long, 14.5 meters wide. The bridge is part of an interstate
highway that has a currently traffic volume of 35,000 Vehicle per day. The unrestricted design
speed is 90 km/hr. The engineer next lists the minimum performance requirements of the structure
that all design proposals must satisfy. The structure must be able to carry the loads prescribed in
Bro 2004 specification. The spans between piers must not deflect more that L/800 meters.
A four lanes conventional reinforced concrete bridge is on of the proposed design alternatives
which satisfied these performance-based requirements during design competition.
The target now is to calculate the total bridge user cost that will incurred by this design proposal
during its whole life cycle.
3.6.2 Application using the developed computer program
The developed bridge user cost model is available and can be order from KTH or from the author,
the model has four windows, the input window, assumption window, work activation and
deactivation window, and the output window. Consequently, using the above mentioned example,
the input data window is shown in Figure 3:6 below.
Input Data Window
Figure 3:6 BUC computer model window No. 1 (Input Data)
- 33 -
3.6.3 Assumptions Window
All of the assumptions are according to the above mentioned system and formulas, but the user can
change them according to the bridge situation. Accordingly, the assumption window is shown in
the following figure.
Figure 3:7 BUC computer model window No. 2 (Assumptions)
3.6.4 Working Tasks Activation Window
According to the bridge type, the user can activate or deactivate of the proposed actions and can
also change the intervals or add other working activities. Consequently, using the above mentioned
example, work activities window is shown in Figure 3:8 below.
- 34 -
Figure 3:8 BUC computer model window No. 3 (Tasks Activation)
3.6.5 Calculation Sheets
The time delay calculation sheets are hidden sheets within the model. Consequently, using the
above mentioned example, the time delay calculation sheets which present the computation system
are presented in Table 3:11 and Table 3:12 as follow.
- 35 -
Table 3:3 BUC Computer model, Time Delay Calculation Sheets
- 36 -
Table 3:4 BUC Computer model, Queued Vehicles Calculation Sheet
3.6.6 Results Window
The forth window is the output window. Obviously the bridge user cost is shown according to
Figure 3:1, which presents the costs according to the project stages and according to the user cost
type. Figure 3:9 illustrate the result of the above mentioned example.
Figure 3:9 BUC computer model window No. 4 (Output)
- 37 -
4. BRIDGE AESTHETICAL AND CULTURAL VALUE
4.1 Introduction
This chapter is a development, adaption, and modification to the appreciating work which carried
out in ETSI II project /SP 3 subproject, by project group which consisting of following persons:
o Dipl. Eng. Seppo Aitta from the Finnish Road Administration
o Civ. Eng. Hans Bohman from the Swedish Road Administration
o Civ. Arch. Eldar Høysæter from the Norwegian Road Administration
o Dr Tech. Aarne Jutila from Insinööritoimisto Extraplan Oy.
4.1.1 Background
Bridges have been part of human settlement for thousands of years. Historic bridges stand as
evidence of the power and influence of past societies. They vary greatly in style and reflect the
culture and engineering innovation of their society.
Bridges are often seen more or less as sculptures and icons to which the citizens may relate as the
soul of the city. This atmosphere and the will to identify the town and its values with an icon may
motivate for bold and spectacular solutions. Some projects have exceeded all cost estimates but still
it has been possible to fulfill them with success.
Modern bridges exploit the latest technologies and construction techniques. They allow us to
challenge the landscape in new ways and so impose our hand on the landscape. It is important to do
so well. Location of a bridge, cultural values of the surroundings, landscape, viewpoints of local
people, and our understanding of the context should guide our solutions. In short, our bridges
should be beautiful.
4.1.2 Objective
The aim of this chapter is to facilitate the evaluation of bridge aesthetical and cultural values and
relate them to the other important aspects of bridge design and construction, i.e., functionality,
economics and techniques.
The second target is to setup some basic design guidelines which can help design teams to produce
bridges of aesthetic value, or at least keep them aware of the bridge aesthetics evaluation process.
4.2 Issues to be Considered
Ranking of bridges and bridge design proposals is a difficult task. Especially difficult it is, if we
have to make aesthetical and cultural values of bridges measurable with other values like cost. At
the first sight the easiest way seems to be to establish some kind of jury to evaluate different
proposal. Of course the judgment of the jury would be based on individual opinions without an
exact scale of measuring. However, an open question still remains: how to convert the judgment to
money that seems to be the only common value available when comparing different things. It is
- 38 -
generally acknowledged, that such a jury in the case of bridge construction should consist of
experts with right education, profession and position, e.g. owners, bridge engineers and architects.
In some cases even ordinary people of the local community could be represented.
For the decision making and to bases the work of the jury, some guiding principles have to be
setup. The main issue to be clearly stated is where to put weight when comparing different
alternatives. This is even more important, if the bridge has special dignity.
In the decision making the following issues have to be considered:
Classification of bridge sites and its corresponding acceptable additional relative costs
The considered items and issues and to give them appropriate weights
4.2.1 Bridge site classification
In Finland the so-called classification of bridge sites is used. This system was developed by the
Finnish Road Administration (Finnra). It considers the value of the scenery. A publication
"Siltapaikkaluokitusohje" (Guide for Grading a Bridge Site) already exists (in Finnish).
A four-grade system is used for evaluation of a bridge site:
o Class I Very demanding considering the landscape and city view.
o Class II Demanding considering the landscape and city view.
o Class III Remarkable considering the landscape and city view.
o Class IV Ordinary considering the landscape and city view.
Class I, “very demanding”. This means that the site includes nation wide valuable views or city
views, culturally valuable landscape or the most important joints in the transport network. Also the
most remarkable waterway crossings within the country and museum bridges belong to this group.
Class II, “demanding”, possess similar characteristics as those belonging to the previous class but
their importance is local, for instance remarkable city or village objects and big bridges crossing
waterways with less modest views.
Class III, “remarkable”, consists of bridge sites including ordinary waterway crossings and bridge
sites at crossings with heavy traffic located outside city or village areas.
Class IV, “ordinary”, consists of bridge sites including roads with low amount of traffic located in
an ordinary landscape outside city or village areas as well as sites with low importance where a
road or railway crosses a waterway. These kinds of bridge sites usually do not require any special
environmental or aesthetical consideration or design.
4.2.2 Cost and aesthetics can be complementary
Bridges of aesthetic merit need not be more expensive than ugly bridges. For example the shape of
a parapet, abutment or pier might have a negligible impact on costs but a significant improvement
visually. However if a bridge is designed to be as cheap as possible then it is unlikely that it will be
of aesthetic value. This is not to say that the cheapest bridge is necessarily the ugliest bridge,
- 39 -
however it does mean that cost and aesthetics as driving forces in the design process need to be
balanced.
‘It is unwise to pay too much. But it is worse to pay too little’
4.2.3 Corresponding acceptable additional costs
The acceptance of some additional cost due to the bridge site class and the aesthetics demands may
be reasonable; consequently an excellent design or bridge may be 30 % more expensive than a poor
solution and could still be chosen.
The relative shares of bridges in the different classes suggested in the "Siltapaikkaluokitusohje"
(Guide for Grading a Bridge Site) are given in Table 4:1. Consequently, the additional costs
compared to the cheapest possible solution are given in the same table.
Table 4:1 corresponding additional relative costs in percentage in the different classes
Bridge Site Class
Item
I
II
III
IV
Number of Bridges (%)
1…2
5…15
65…75
15…25
Additional cost allowed
0…30
0…20
0…10
0
No additional cost is allocated to bridges belonging to Class IV
4.3 Bridge Aesthetics Design Guidelines
For aesthetics to be successful, it must first be considered. It should be an integral part of design
and must be considered both in the general form and all the details that support it. The parts must
be considered as to how they contribute to the whole.
Generally bridges seem aesthetically more pleasing if they are simple in form, the deck is thinner
(as a proportion of its span), the lines of the structure are continuous and the shapes of the structural
members reflect the forces acting on them.
The aesthetics of a bridge should be considered at the conception of a project and through every
stage of development. Aesthetics is not something that can be added on at the end, it is the
final product of the planning, design and procurement process, from initial route selection,
through environmental assessment, to detail design and construction.
4.3.1 Sensitivity of the bridge type to the context and simplicity
- 40 -
Perhaps the most fundamental response to context is the choice of bridge structure. In most
instances it is span length that is the most significant factor in determining the form (and cost) of a
bridge. Bridges with a horizontal form are generally preferable to bridges on a grade over flat
simple landscapes and significant expanses of water. This can be shown in the following figure.
Bridges with a horizontal form are generally preferable
Figure 4:1 Proper bridge horizontal form
The accepted approximate relationship between span and superstructure type is as
follows.
o Short span (up to approximately 18m): pre-stressed concrete plank bridges.
o Short to medium span (approximately 18-40m): pre-stressed concrete girders or pre-
stressed concrete voided slabs.
o Medium span (approximately 40-80m): steel or post-tensioned concrete box girders
or incrementally launched girders.
o Medium to long span (up to approximately 300m): balanced cantilever.
o Long span (up to approximately 800m): cable stay.
o Very long span (longer than 800m): suspension bridges.
- 41 -
4.3.2 The bridge form as a whole
Proportion
The dictionary defines proportion as the proper relationship between things or parts.
Depth to span ratio
The proportion between depth of superstructure and bridge spans is an important ratio. It is
referred to the slenderness of the bridge and is defined as the span length divided by beam
depth. Common ratios can vary from 5 to 30. The ratio of five can result in a very chunky
bridge although with appearance of strength while 30 can lead to very slender bridge. For a
common pier and girder bridge, ratios generally vary between 15 and 20. These notations
and recommendations are given in Table 4:2.
Table 4:2 Proper proportions guidelines
Depth to span ratio
Bridge with a slenderness ratio of
approximately 1:12.
Captain Cook bridge, a slenderness ratio
of approximately 1:18.
Deck to parapet depth ratio Span to parapet depth ratio
The ratio of deck overhang relative to
parapet depth is also considered a significant
aesthetic proportion and guidelines have
been developed by Cardiff University School
of Engineering.
A ratio has been developed by Frederick
Gottemoeller in his book for the relationship
between span and depth and parapet height.
These formulae form the basis for a guide to
visual proportions.
- 42 -
Symmetry, Order and rhythm
Symmetrical bridges are often more aesthetically pleasing than nonsymmetrical bridges and
symmetry should not be departed from unless for a good reason. Figure 4:2 schematically
present the affects.
Rearranging the parts provides an ordered and pleasing whole
Figure 4:2 Bridge Symetry apperancess
Unity of design and detail important
Careful consideration of interrelationship of each element, and their relationship with the whole is
necessary at all stages of the design process. Good detailing is essential to good bridge design and
lack of attention to detail can spoil an otherwise beautiful bridge.
4.3.3 The bridge Parts
Superstructure
Parapet
The outer face of the parapet can be one of the most important aesthetic elements of a beam bridge.
It is the highest piece of the bridge and often the most dominant in long distance views. The
following principles (Figure 4:3) should be considered in the design of the parapet.
Figure 4:3 Proper parapet design principle
- 43 -
Girder elevation
Table 4:3 Proper girder elevation design guidelines
Hunched girders are expressive and
responsive to the forces in the bridge. They can
often be more distinctive and elegant than single
depth beams
Long haunches smoothly tapering out are
much more graceful and responsive than short
abrupt haunches.
Three or five span haunches are aesthetically
very elegant balanced structures.
Avoid a sharp angle between haunch and
beam.
Girder cross section
Table 4:4 Proper girder cross section design guidelines
Maximizing the overhang will increase the
shadow
An angled connection will minimize this effect
A very acute angle provides a deep
shadow nearly all of the time
A curved soffit will provide a gradation of tone
and minimize a sharp line at the base of the
beam.
- 44 -
Substructure
Headstock
When they are used they draw attention to the pier and the method of support, if avoided
they better allow the superstructure to dominate the bridge view. Table 4:5 schematically
present the affects.
Table 4:5 Proper Headstock design guidelines
The headstock and pier combination on this
bridge adds unnecessary complexity and detail
If possible headstocks should not extend
across the outer face of the girder. This
introduces unnecessary complexity and
appears in elevation as if the headstock is
supporting the deck rather than the girder
Abutment
Table 4:6 Proper abutment design guidelines
Visible size
Spill through abutments allow open views to the
landscape and better visibility to the road beyond.
Reducing the abutments can create a
more refined and better looking bridge. It
does however increase the span and
therefore depth of beam.
Placement
Continuing the superstructure or the parapet allows
the shadow line to reduce the dominance of the
abutment, and makes the bridge appear longer and
more elegant.
Shape
Angling the abutments provides a more
open sleek look and helps visually anchor
the span.
- 45 -
Piers
Table 4:7 Proper Headstock design guidelines
Longitudinal pier spacing
Too many piers can appear cluttered, while too few
piers can result in an overly dominating deep beam,
a balance is required
Multiple piers
When placed too closely multiple piers can
appear complex or wall like, Collecting
multiple piers into pairs or clusters can open
up views below the deck and also give
rhythm and elegance to the supports.
Pier cross section
Pier shapes with only two lines of symmetry (e.g.
ellipses or rectangles) and transverse to the
centerline of the deck are preferable to squares and
circles as they present the thinnest edge to the side
view. Rounding off the corners of rectangular
piers provides a softer form, which may be
preferable in certain contexts
Pier short elevation
Pier shapes which have a slight taper can
add elegance by visually adding weight to
the bottom where stresses are greatest,
economically a taper of around 1:80 is
desirable the reverse taper should only be
used where the appearance of rigidity is
required between superstructure and pier.
Pier long elevation
A taper can appear elegant and better represents
the structural forces acting upon the pier
One significant advantage with a reverse taper is
that it facilitates the elimination of the headstock
- 46 -
Details
Table 4:8 Proper bridge details design guidelines
Joints and connections
A nice joint can enhance the bridge design and
provide another level of detailed aesthetic
interest.
Bridge barriers & Railings
A two rail barrier is better than a single
rail barrier in this respect
Safety screens
An outward curving screen creates a more open
feeling for bridge users and reduces the
opaqueness of the top of the mesh for road users.
However it presents a greater apparent depth of
structure for onlookers.
The screens should extend to the ends of the
bridge span.
Lighting and color
The light columns should relate to the other
bridge elements in position and form. Where
possible lighting on bridges should be
minimized or avoided.
A neutral palette of black, grays and white
colors tend to give a clear definition of the
bridge as an object in the landscape.
- 47 -
4.4 Unique Evaluation System
4.4.1 Body of the system
The system is based on the idea that points given to different things according to a given scheme
and the opinion of the evaluators. The number n of things to be considered can be freely chosen
and each thing can have different weight w
i
of importance.
The evaluator rule is to give a numerical values or points p
i
on a chosen scale to each thing i
that is considered.
For each thing i the scale can be different, but essential is, that the extreme values p
imin
and
p
imax
are related to each other so that always
For evaluating the effect of aesthetical and cultural aspects, Aesthetical coefficient k
AES
calculated
by the equation
Here a is another non-dimensional scaling factor by which the effect of these aspects can be
regulated. Finally, the relative aesthetical and cultural value cost C
RACV
of a design or a bridge, is
then obtained by equation
Here C
AG
is the Agency cost obtained by cost calculation considering the construction, repair,
maintenance and demolishing costs of the bridge from its whole lifetime. Consequently, the final
life cycle cost of the bridge LCC is
Where:
o C
AG
is the corresponding Agency cost.
o C
USER
is the corresponding User cost.
o C
RACV
is the corresponding Relative Aesthetical and Cultural Value cost.
o C
REI
is the corresponding Relative Environmental Impact cost.
The system described above enables comparison between different design proposals, existing
bridges and bridge types as well as evaluation of even different construction methods.
?
?
=
=
? =
n
i
i i
n
i
i i
AES
p w
p w
a k
1
max max
1
REI RACV USER AG C C C C LCC + + + =
AG AES RACV C k C =
max min Pi Pi ? =
- 48 -
075 ,
10
5
15 ,
) 2 3 ( 2
) 1 1 ( ) 2 2 (
15 , ? = × ? =
+ ×
× + ×
× ? = AES k
4.4.2 Numerical values for p
i
and a
The scale for points p
i
and the corresponding individual values should be chosen so that an
evaluator has enough possibilities to distinguish the different designs or bridges, but at the same
time not too many categories to keep the evaluation process simple. That is why it is proposed
that
a) The scale for each item is the same,
b) The scale varies from -2 to +2
c) Only five categories with even steps are used.
When so, the extreme values p
imax
have a constant value p
max
= 2 and the categories are as
presented in Table 4:9.
Table 4:9 Numerical values for the evaluation system and its meaning
Category Explanation
-2 Poor
-1 Modest
0 Medium
1 Good
2 Excellent
For the non-dimensional scaling factor a numerical value a = 0.30 is recommended as it used
also in (Guide for Grading a Bridge Site) are given in Table 2. That means that in the extreme
cases the Aesthetical coefficient k
AES
varies between -0.30 and +0.30. This may be reasonable,
because consequently an excellent design or bridge may be 30 % more expensive than a poor
solution and could still be chosen.
With the values mentioned above Eq. (2) takes a reduced form
To demonstrate the system above, let us take a simple artificial example. Let us assume our
bridge is belonging to class II, and we have only two things to consider: aesthetics and culture.
Let us consider weight w
1max
= 3 and the latter one weight w
2max
= 2 (weights belonging to the
maximum case, case I). Let say in bridge case II the former one have weight w
1
= 2 and the latter
one weight w
2
= 1. Let us further assume that our bridge was given 2 points for its aesthetical
values, i.e., p
1
= 2, and 1 point for cultural values, i.e., p
2
= 1. Thus the Aesthetical coefficient
k
AES
takes the value
?
?
?
?
?
?
=
=
=
=
=
=
? = ? = ? =
n
i
i
n
i
i i
n
i
i
n
i
i i
n
i
i i
n
i
i i
AES
w
p w
w
p w
p w
p w
a k
1
max
1
1
max
1
1
max max
1
15 ,
2
3 , 0
- 49 -
Which means that, because the bridge proposal that we are evaluating is beautiful or have
a good value of aesthetics and culture, so it will reduce the agency cost by = 0,075 = 7,5 %.
In case where k
AES
is (+ ve), that’s mean the proposal that we are evaluating is ugly or have bad
aesthetical and cultural value, so it will increase the agency cost by the value of k
AES
4.4.3 Bridge site classes
The same four classes which used in the publication "Siltapaikkaluokitusohje" (Guide
for Grading the Bridge Site) mentioned above. According to that publication, there are
four different bridge site classes as follows in Table 4:10
Table 4:10 Bridge site classes and its meaning
Class Explanation
Class I Very demanding
Class II Demanding
Class III Remarkable
Class IV Ordinary
That means that Class IV is the lowest one and does not require any special aesthetical attention,
where no additional cost is allocated to bridges belonging to this class (Table 3.2).
4.4.4 Recommended considered evaluation items
The numerical values w
i
recommended here are dependant on the bridge site classes. For a
computer program to be developed, the user is then supposed to evaluate these items according
to the proposed scale. Depend on particular cases, the user is supposed to change these values
to more suitable values or some times neglect or add other things, if needed. The recommended
consider items are presented in Table 4:11 as follow.
- 50 -
Table 4:11 List of the evaluation considered items and its weight factors in each bridge site class
4.5 Practical Application and Testing
4.5.1 The case background
As a practical application of how we handle aesthetics, we can look at the current (2009) bridge
over the Motala Bay in the Middle of Sweden. In order to get a nice and beautiful bridge, a
bridge design competition was arranged. Seven architectural firms were invited to participate.
Nine different proposals were sent in to the Swedish National Road Administration.
The proposals on, how to design the bridge, should contain a lot of documents describing the
bridge from a lot of different aspects as:
The Motala Bay Bridge is located in a small town called Motala. The town was founded in 1822
and has 30 000 inhabitants. It is situated in the western part of Östergötland by the Göta Canal
outlet into Sweden’s second largest lake, Lake Vättern, right between Stockholm and
Gothenburg. The bridge - still in design phase in early 2009 - crosses the Motala Bay and will be
about 600 meters long. The map of the building site is shown in Figure 4:4
- 51 -
Figure 4:4 Map of the Motala Bay Bridge area.
4.5.2 The considered design proposals
Three design proposals are considered here.
Proposal Nr. 1 is a continuous steel-concrete composite box girder bridge with inclined struts
supporting the side cantilevers and inclined V-shape legs made from steel around the main span
that is 156 meters long. The side spans are 72 and 123 meters on one side and 123, 72 and 42
meters on the other, altogether six spans. The sum of spans is 588 meters and the total length 610
meters (Figure4:5 and Figure 4:6).
On both sides of the bridge there is a pedestrian and cycling lane slightly below the road level.
The cross-section is symmetric with respect to the center line of the bridge and constant
throughout the bridge. The steel box part of the superstructure is supported by the sub-structure.
Longitudinally the bridge is symmetric with respect to the waterway, but outside that area it is
not. Due to the modest structural depth, 4 meters, the height of the bridge remains relatively
small reducing the maximum slope to 35 %
0
. Vertical clearance under the bridge is 22,5 meters
on a length of 40 meters. Embankments are not steeper than 1:2. Indirect lighting and spotlights
on the inclined legs will be provided. The traffic density on the bridge will be about 6300
vehicles per day.
- 52 -
Figure 4:5 Side view of the bridge according to Proposal Nr. 1.
Figure 4:6 Perspective view of the bridge according to Proposal Nr. 1
- 53 -
Figure 4:7 Side view of the bridge according to Proposal Nr. 2
Proposal Nr. 2 is a continuous steel-concrete composite box girder bridge with a long arch span,
191 meters, in the middle. The bridge consists of nine spans: 40+3x48+191+3x48+40 = 559
meters. The arch is made from steel. The width of the bridge is 23 meters. The height of the
bridge is 25,5 meters and vertical clearance in the main span is 22,5 meters on a length of 40
meters. The arch is curved in horizontal plane just as the girder, too. There is a pedestrian and
cycling lane on one side of the deck (Figure 4:7 and 4:8 and 4:9). The traffic density on the
bridge will be about 6300 vehicles per day. The design life length of the bridge is planned to be
120 years.
- 54 -
Figure 4.8 Perspective view of the bridge according to Proposal Nr. 2.
Figure 4.9 Perspective view of the bridge according to Proposal Nr. 2.
- 55 -
Figure 4.10 Perspective view of the approaching span according to Proposal Nr. 2.
Proposal Nr. 3 is a continuous prestressed concrete box girder bridge whose 6 out of 13 spans
are supported by cables. So the bridge actually is a combined box girder and cable-stayed bridge.
Its spans are 36+2x54+60+4x72+60+3x54+42 = 756 meters. The total width of the deck is 24,7
meters. In the cable-supported spans there are four and in the other spans 5 boxes side by side. The
deck is unsymmetrical with respect to the center line of the bridge and to the cable planes that
are located in the middle of the bridge. There is a pedestrian and bicycle lane only on one side
of the bridge. The five pylons supporting the stay-cables form a monolithic structure with the
superstructure without any joints. At the other piers, however, and at the abutments the
superstructure is supported by bearings. The design life length of the bridge is planned to be 120
years. Photomontage views of the bridge are shown in Figure 4:11, 4:12, and 4:13.
- 56 -
Figure 4:11 Side view of the bridge according to Proposal Nr. 3
Figure 4.12 Perspective view of the bridge according to Proposal Nr. 3.
- 57 -
Figure 4.13 Perspective view of the approaching span according to Proposal Nr. 3
The following figure presents the three design proposals including superstructure and the whole
bridge cross section for each alternative.
Figure 4:14 Conclusion of the given data in the three proposals
- 58 -
4.5.3 The evaluation process
The testing procedure was carried out so that each of the four evaluators studied the documents
available and then individually tried to evaluate first the bridge site and then the proposals
themselves. Finally the outcome was compared and discussed.
The bridge site classification
Evaluation of a bridge site should be based on maps and documents available and on site visits.
Four different items were evaluated and the corresponding bridge classes were determined
corresponding to each item. Consequently the final bridge site class could be determined. The
process is described in Table 4:12.
Table 4:12 The process used in the evaluation of the Motala Bay Bridge class
Evaluated item Class Arguments
Location of the bridge site II
The bridge site is located between two inhabited
islands. There is settlement on both shores and due
to that the daily traffic is considerable.
Furthermore, the road leading to the ferry is part of
the archipelago ring road that is kept open for
tourists in summer time. The bridge will replace the
present ferry.
Value of the landscape I
Björkö and Mossala villages with there storehouses
on shore are considered as a valuable landscape
even on countrywide level. The bridge site is part
of this valuable cultural landscape.
Cultural value of the
bridge site
II
Important environment considering the history of
the area. In the vicinity there is the Lills-Kills croft
that is protected by the support of the building
protection law.
Aesthetical demands of
the bridge
II
The bridge is part of valuable landscape. The
bridge may not be a too dominating element but
shall be suited to the nearby surrounding.
Overall evaluation of the
bridge site class
I-II Especially demanding or demanding bridge site.
After a short discussion, however, it was not difficult for the evaluators unanimously to agree that
the bridge site class in this case is Class II (“Demanding”). That fixed the weights accordingly
(Table 4:11).
Evaluation of the bridge proposals themselves
The most difficult part is to define the considered items and the weight factors for the
different items in each of the three cases, followed. Consequently, value 0,30 for the scaling
factor a was accepted. The item list was agreed to be the one proposed in this report Table4:11.
- 59 -
Consequently, according to Table 4.11Class II
Thus, Consequently:
The complete results of the evaluation are presented in a compact mathematical form below. The
Aesthetics coefficient kAES is of main concern. In this particular case (bridge site class II)
According to Table 3.12 Class II, to cover all evaluation cases, a matrix presentation is used. Thus,
weight vector {wi} is:
Where {kAES} is the final Aesthetics coefficient vector dimension 1x5, (pi) is the evaluation result
matrix, dimensions 5x20, which in this case has the value
?
?
?
?
=
=
=
=
? = ? = ? =
20
1
20
1
1
max max
1
II) (
II) (
0015 .
200
30 . 0
i
i i
i
i i
n
i
i i
n
i
i i
AES p w
p w
p w
p w
a k class
class
? ?
= =
= + + + + + = =
n
i i
iclass i w w
1
20
1
100 6 .. .......... 4 6 6 12 1 max
[ ] [ ] 4 3 3 2 3 2 3 2 3 3 5 4 4 4 2 2 3 4 4 8 II) ( = class i w
200 100 2 2 1
20
1 1
max max = × = =
? ?
= = i
n
i
i i iclass w p w
- 60 -
In the case of Proposal Nr. 1 the evaluation result matrix {pi} takes the form
In the matrix, the first column represents the points which the first evaluator gave to the twenty
different items. The points are listed in the same order as in Table 4:11, or in the list just above Eq.
Similarly, the second column consists of the points given by the second evaluator, and so on until
the fourth column, which is related to the fourth evaluator. The values in the fifth column are
simply the roundup average values of the four previous ones on the same row.
When the operation shown by equations is carried out using the numerical values presented in
above, the final results will be as follow.
{ } { } 114 . 134 . 102 . 104 . 108 . ? ? ? ? ? = ASE k
The same for Proposal Nr. 2, the final aesthetics coefficient vector {kAES} takes the form:
{ } { } 128 . 142 . 122 . 121 . 118 . ? ? ? ? ? = ASE k
Similarly for Proposal Nr. 3 final Aesthetics coefficient vector {kAES} takes the form:
{ } { } 074 . 091 . 041 . 064 . 084 . ? ? ? ? ? = ASE k
The test carried out shows that the evaluation method developed is easy to use and
[ ]
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
¸
(
¸
? ? ? ?
=
1 0 1 2 1
2 2 2 1 1
1 1 1 2 1
1 2 1 0 2
2 1 2 2 2
1 1 2 1 1
1 1 2 1 0
1 2 1 1 0
2 2 1 2 2
1 1 1 0 1
1 0 1 2 1
1 1 1 2 1
1 1 1 1 2
1 2 2 1 0
1 1 1 0 1
1 1 0 2 2
2 1 2 1 2
2 2 1 1 2
1 2 1 1 1
1 2 0 1 1
i p
- 61 -
mathematically simple. The judgments of the four evaluators were in most cases surprisingly
similar. Although some differences appeared in some details, they were greatly balanced out in
the final result. The smallest differences are in the cases of Proposal Nr. 1 and Proposal Nr. 2,
where the Aesthetics coefficient k
AES
varies between -0,102 and -0,134, and -0,118 and -0,142,
respectively. In the case of Proposal Nr. 3 the variation is bigger, from -0,041 to -0,091, but
even in this case every evaluator comes to the conclusion that the aesthetical and cultural values
of the proposal are positive. Based on these results Proposal Nr. 2 seems to be slightly
superior to Proposal Nr. 2 and Proposal Nr. 3. And it occupies the last position in this
evaluation.
Better than to compare the judgments of individual evaluators might be to compare the average
values. According to Eqs., the variation between the different proposals is extremely small, from
-0,114 to -0,128 in the average values. Maybe the average value give more objective result, when
there are several evaluators, as it was the case in the test evaluation carried out. The final order
between the three proposals, however, is still the same: Proposal Nr. 2 is slightly superior to
Proposal Nr. 2 and Proposal Nr. 3 occupies the last position
4.6 Developed Computer Program
As a culmination of progress in this chapter and its unique aesthetics evaluation system, a simple
computer program is developed. The program is composing all of the things which is explained
and mentioned in above in a very simple systematic way. The program can as easily be used by
an individual as by a jury or group of evaluators. The front page shape is as shown in Figure 4:15.
- 62 -
Figure 4:15 shape of the developed computer program
4.6.1 Introduction
Practical use of the program is simple, only 4 steps to get the bridge proposal equivalent
aesthetical and cultural coefficient K
AES
o, the user is only have to chose the alternative form a
build up list of choices, he don’t have to enter any other values, or perhaps he may have to, if he
decided to change the weight factors of the considered items to suit down his case of study.
- 63 -
4.6.2 Working steps description
The first Step is to agree about the value the scaling factor a. It also needs to be determined in
advance, because it has a decisive influence on the level of appreciation of aesthetical values
compared to costs. The value 0,30 is recommended and its sounds reasonable, because in extreme
cases it restricts the effect of aesthetics up to ±30 %, but of course also any other value between
is possible. Even this value should be determined by the bridge owner. In Finland the are usually
using a=0,30 as its mentioned in Table 3.12
The second step is to evaluate the bridge site by determining which class the bridge site is
belongs to. However, four items have to be evaluated to reach this target and so the average
value of these four items will be the class of the bridge site.
The third step is to agree about the items that will be evaluated and to determine weight of each
item. This should be done before the evaluation process begins. The weights should be
considered as “fixed values” and may not be changed during the evaluation process. One is
totally free to choose any items and their number is by no means restricted.
Too detailed item may cause difficulties to the evaluator. In this program, almost a standard list
of items and there weights is included, which fairly cover the general bridge aesthetics demands,
it can easily be altered to meet the requirements of the project in question, whether by giving
“zero weight” to those items that are left outside consideration or/and by adding new item by
changing the last cell name form others to the new name, and give it the suitable weight factor in
each bridge site class.
The forth and final step includes the evaluation itself, i.e., the determining of points p
i
for each
considered item, however, a fixed scale is determined with p
max
= - p
min
= 2, with steps equal to 1
here one has to decide between five different values, i.e. -2, -1, 0, 1 and 2, according to his point
of view. It can be done by choosing the value form a buildup list beside each considered item.
In case of individual user, he can chose the points p
i
easily form each list according to his view
point, simply if there is a jury or group of evaluators they can use this program by entering the
average evaluation value for each consider item.
When the evaluator has decided on points p
i
, it is a simple mathematical task to calculate the
final values of Aesthetics coefficient k
AES
and all of these equations are built up in this program.
4.6.3 Example
Let us take a simple example, which may illustrate the procedure better, Let us consider the case
of average evaluation in the previous example for proposal number 1, by keeping the same value
of a=0,30 and the bridge site is belong to Class II. The average evaluation from the matrix, which
is column number 5, which is as following:
- 64 -
{ } { } 1 2 1 1 2 1 1 1 2 1 1 1 1 1 1 1 2 2 1 1 ? = Pi
Figure 4:16 Practical example in the developed program
- 65 -
Figure 4:16 describes the usage and the application of the model. By entering this values of points
p
i
in the program, consequently the value of Aesthetics coefficient k
AES
= -0.114 which is the same
value that on equation number (11) column number 5.
According to the proposed list of items and its weight factors and the recommended value of
a=0.30, the extreme values of the Aesthetics coefficient k
AES
will be as followed in table 4:13.
Table 4:13 The extreme values of the Aesthetics coefficient k
AES
according to table 3.12 data
a=0.30 Class I Class II Class III Class IV
Excellent Design K
AES
max -0.30 -0.204 -0.096 0
Bad Design K
AES
min 0.30 0.204 0.096 0
4.6.4 Practical use of the program
The program is concluding a unique system that enables to incorporate aesthetical values to
bridge design or construction projects and to make them comparable with construction and
lifecycle costs. The method can be used beneficially in the following cases:
o Evaluation of aesthetical values with respect to the initial construction costs.
o Comparison of different bridge design proposals within a project or in
engineering skills - including bridge design - competitions.
o Comparison of different routes where bridges are involved during the feasibility
study stage or construction phase.
o Rewarding - or punishing - of those involved when an aesthetically better - or
worse - result is achieved than expected.
The method can as easily be used by an individual as by a jury or group of evaluators. Due to its
simple mathematical formulation it can also be easily incorporated in a LCC computer program
to become part of it.
- 66 -
5. BRIDGE ENVIRONMENTAL IMPACT
5.1 Introduction
Environmental indicators demonstrate significant impacts of current concrete infrastructure
systems. Construction, maintenance and demolition of bridges demand materials and energy inputs,
which in turn lead to environmental impacts. New infrastructure and maintenance of existing
infrastructure has led to a global output of construction-related concrete that exceeds 12 billion tons
per year (van Oss and Padovani 2002b). This enormous volume represents huge flows of material
between natural and human systems, which is expected to increase significantly as world
population urbanizes (UNFPA 2001). Cement production accounts for 5% of all global
anthropogenic carbon dioxide (CO2) emissions (Hendricks et al. 1998, Worrell 2001) and
significant levels of SO2, NOx, particulate matter and other airborne pollutants (WBCSD 2002, US
EPA 1999, US EPA 2000).
5.2 Issued to be Considered
5.2.1 Project development stages and considerations
Modeling the complete life cycle of a bridge system is complex and data intensive. When we talk
about the bridge environmental impact we have to put in mind to consider all bridge life cycle
stages, as shown in Figure 5:1, considering the input and the output as well. The main parameters
that should be considered during the assessing process are as follow.
Figure 5:1 Bridge LCA path
Material resource consumption (The Usage of un renewable materials)
Air and water pollutant emissions
Solid waste generation
Energy use
Fuel consumption
Emissions from the traffic
- 67 -
5.2.2 Toxics Classification
There are thousands of chemicals affecting human health and the environment, hundreds of
different known mechanisms and many other unknown or incompletely known mechanisms. While
toxicologists would not normally combine compounds unless common models of action have been
demonstrated, LCA add all toxics into one overall score even if modes of actions are known to be
different.
Each of all the various environmental stressors throughout the life cycle, relative to the functional
unit, are summarized and then classified into impact categories, according to which environmental
impact(s) the stressors contribute to. Established impact assessment methods cover various impact
categories, like for instance global warming, acidification, toxicity etc. This method includes
characterization factors for 10 impact categories as shown in Figure 5:2; Abiotic depletion potential
(ADP), acidification potential (AP), eutrophication potential (EP) global warming potential (GWP),
ozone layer depletion potential (ODP), human toxicity potential (HTP), fresh water ecotoxicity
potential (FAETP), marine aquatic ecotoxicity potential (MAETP), terrestrial ecotoxicity potential
(TETP) and photochemical ozone creation potential (POCP). However, the 4 toxicity categories
are, for the time being, omitted in BridgeLCA, due to high uncertainties in the calculation principles
of these.
Figure 5:2 Bridge emissions categories
5.2.3 Toxics categories weighting impacts
The best way is to calculate the environmental impact per category using characterization
indicators. These indicators are based on the physicochemical mechanisms of how different
substances contribute to the different impact categories. E.g. Global-warming potential is one of the
environmental categories and CO2 is the equivalent for this category. Methane that is a green house
gas which contributes 23 times as much to global warming than CO2, is multiplied with a factor of
23, and added to the category as CO2-equivalents.
Environmental Impact LCA
ADP
GWP
ODP
HTP
FAETP
MATEP
TETP
PCOP
AP
EP
Used materials during
the whole bridge life cycle
- 68 -
The following graphs (Figure 5:3) present normalized and weighted results. Normalization is done
by dividing the impacts per category by the average emissions (relevant for the respective category)
per person per year, in Western Europe in 1995. Further, the normalized results are multiplied by
weighting factors, which is a measure of the categories’ relative importance. The weighting factors
used here are taken from the BEES software, and are determined by the Environmental Protection
Agency (USA).
Figure 5:3 Environmental Protection Agency (USA) emissions weighting factors
5.2.4 Life cycle assessment (LCA)
Life cycle assessment is an analytical technique for evaluating the full environmental burdens and
impacts associated with a product system (ISO 1997). Life cycle assessment is a global tool,
calculating burdens throughout the life cycle of a product, material or service. Its strength is that it
quantifies all possible environmental burdens; its weakness is low spatial and temporal resolution.
5.3 Presentation of Previous Studies
There are only few scientific publications available on the topic of environmental effects of
bridges; the relevant articles are briefly presented in this section.
Comparison of different bridge deck component alternatives
Keoleian and Kendall, compare two types of deck systems; a steel-reinforced concrete deck with
conventional steel expansion joints and a steel-reinforced concrete deck with a link slab design
using a concrete alternative (Figure 5:4); engineered cementations composites (ECC). ECC is fiber
reinforced and has a strain capacity 500-600 times higher than normal concrete. It also prevents
nearly all corrosion of girders by reducing leakage of corrosive elements usually occurring through
worn expansion joints. Corrosion of steel girders is one of the main causes for replacement of deck
and superstructure. The study includes material production, construction, use and end-of-life
management related to bridge the decks. Initial bridge construction is similar for both studies and
- 69 -
therefore omitted. Three reconstruction options are considered; bridge deck replacement, deck
resurfacing and repair and maintenance (mainly fixing of cracks and potholes). Traffic disruption
during these activities is also included. Various air and water pollutants are considered5. The ECC
link slab deck is assumed a lifetime twice the lifetime of the deck with conventional joints.
Conclusions made in the analysis are that the ECC deck yields significantly lower environmental
impacts, for all pollutants, mainly because of less need for maintenance. For both deck systems, the
construction and repair related traffic turn out to be significant for the environmental performance.
It is also concluded that prediction of maintenance and repair schedules for each system is critical
in evaluating the performance of alternative materials.
Figure 5:4 Keoleian and Kendall comparison case study
Comparison of bridge types and designs
Collings presents two studies where three bridge types and three bridge designs are compared,
respectively. The bridge types compared are a concrete cantilever bridge, a concrete cable stay
bridge and a steel arch bridge. Relative costs and CO2 emissions for the material consumptions and
the use phase of the bridges are considered. The main conclusions are that both costs and emissions
are highest for the steel arch bridge, actually twice as high as for the concrete cantilever bridge that
gives the lowest costs and emissions. Paint, waterproofing and plastics have relatively high values
per ton of embodied energy and CO2 emissions.
The bridge designs compared are a profiled girder bridge, a tied arch bridge and a cable-stayed
bridge, designed for a longest span of 120 m, and 3 smaller spans (66 m in total) at each end. Three
material choices for each design alternative are assessed. The embodied energy and CO2 emissions
from the construction phase and the CO2 emissions during the lifetime of the bridge are given,
assuming a lifetime of 120 years. Maintenance activities included are repainting, bearing
replacement, re-surfacing and re-waterproofing. Traffic disruption due to maintenance is also
included. The main conclusions from this study are that concrete bridges have lower embodied
energy and CO2 emissions. More architectural designs like leaning or distortion of elements have
larger environmental impact, as they require more materials and more complex construction.
Emissions during the use phase are approximately the same for the three material alternatives. The
maintenance activity causing most of the emissions in the use phase is resurfacing of the bridge.
The traffic disruption due to repair and maintenance are a highly uncertain parameter, as it depends
on amount of traffic, proportion of lorries and diversion distance.
- 70 -
5.4 Case study
BridgeLCA is computer program developed in the ETSI Stage 2 by Johanne Hammervold, based
on the use of three case bridges; one steel bridge, one concrete bridge and one wooden bridge. The
bridges are already built bridges in Norway, and are thus not planned for the same location. They
differ in size and are not directly comparable. The concrete bridge, Hillersvika, has longer
construction length and width, and thus requires the most materials. The steel bridge, Klenevågen,
is the shortest bridge. An overview of the bridges and key parameters are given in following Table:
Table 5:1 BridgeLCA case study parameters
5.4.1 Total weighted results
Total weighted results, given in Figure 5:5, show that Klenevågen (steel box girder bridge) causes
the highest impacts, closely followed by Hillersvika (concrete girder bridge). Fretheim (wooden
arch bridge) causes roughly half the impacts as Klenevågen. The most important categories in total
weighted results are Global Warming Potential (GWP) and Abiotic Depletion Potential (ADP) for
all three bridges. Acidification Potential (AP) is also a relatively important category, while Ozone
Depletion Potential (ODP) is negligible in these results.
Figure 5:5 Case study total weighted result
- 71 -
5.4.2 Result per bridge and category
The impacts caused by material and energy consumptions related to various bridge as totals per
bridge and impact category as given in Table 5:2 below. In the category Abiotic Depletion Potential
bridge equipment and the use phase (OR&M) also contribute substantial shares of the impacts. This
is mainly caused by the surfacing of the bridges. The original surfacing is part of the bridge
equipment, and re-asphalting is performed each 10
th
year throughout the lifetime. Asphalt, asphalt
membrane and mastic are all bitumen products, which consume raw oil in production which again
causes the impacts to the ADP category.
For all three bridges, the construction phase causes a small share of the impacts to all categories.
The construction phase includes use of formwork and building machines and transport of workers
and materials. The results show that these factors are of less importance in this analysis.
Table 5:2 Total results per bridge and category
5.4.3 Impact per m
2
surface area of the bridge
Table 5:3 show the impact for each category per m
2
of the bridge surface area. It is important to
keep in mind that a comparison per m2 will neither give directly comparable results. The material
and energy consumptions, and also transport services and operation, repair and maintenance
activities will not vary linearly relative to bridge size. One example is the abutments; the size of
these will not change if bridge length is changed, but it will change if the width of the bridge is
changed. The main load-bearing systems and their consumption of materials will differ with bridge
length and width, but only to a certain degree, and definitely not linearly.
Table 5:3 Impacts for each category, per m2 surface area of bridge
Finally, the Relative Environmental Impact cost C
REI
of a bridge, is then obtained by equation:
o k
EI
Is the environmental impact coefficient. Range from 0,0 To +0,20
Could complement information to be used in the topic, but is not presented here. For more
information see ETSI Stage 2.
AG REI C k C EI =
- 72 -
6. SUMMARY
6.1 Conclusion and Discussion
This master thesis was devoted as a research study within ETSI project, which is a Scandinavian
contributed project. ETSI project is contributed between three Nordic countries, Sweden, Norway,
and Finland. The main task of the ETSI project is to develop a Nordic unified methodology and
computer program for bridge LCC calculations.
The idea behind this study is that, bridges investment decisions should consider all of the costs and
considerations incurred during the period over which the alternatives are being compared. Bridges
are required to provide service for many years. The ability of a bridge to provide service over time
is predicated on its being maintained appropriately by the agency. Thus the investment decision
should consider not only the initial activity that creates a public good, but also all future activities
that will be required to keep that investment available to the public. It is important to note that the
lowest agency cost option may not necessarily be implemented when other considerations such as
aesthetical and cultural value, user cost, and environmental concerns are taken into account.
This research study demonstrates a unique methodology and present a new systematic way for
analysis, evaluation, and optimization of the bridge life cycle indicators like agency cost, user cost,
aesthetical and cultural value, and the environmental impact. Present a unique flexible system
integrating all of bridge life cycle issues and make them measurable and comparable like the bridge
initial cost.
Based on this unique evaluation system, two computer programs were developed to facilitate the
usage, one for calculating the bridge user cost and one to evaluate the bridge aesthetical and
cultural value. The application of this integrated model to bridge design highlighted a critical
importance of using the life cycle modeling in order to enhance the sustainability of bridges
infrastructure systems.
6.2 Recommendation and Further Research
The application of this integrated model to bridge design highlighted the critical importance of
using the life cycle modeling in order to enhance the sustainability the bridges. Fields for future
research and development can be in the following issues.
o Sorting and gathering of agency historical data to feed the LCCA process
o Degradation models for all kinds of bridges and their structural elements.
o Tools for transforming degradation models into timings for MR&R actions.
o Methodologies for describing bridges both regarding their measures, structural parts
and their conditions.
o Development of the proposed two computer models
- 73 -
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ETSI PROJECT (Stage 1) Bridge Life Cycle Optimisation
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ETSI PROJECT (Stage 2) Bridge Life Cycle Optimisation
Håkan Sundquist and Raid Karoumi. TRITA-BKN. Report 128 ISSN 1103- 4289 ISRN KTH - 128 -
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Transportation Research Record No 1490, p.23-31, National Academy Press, Washington D.C.
Keoleian, G.A., et al. Life cycle modeling of concrete bridge design: Comparison of engineered
cementitious composite link slabs and conventional steel expansion joints. Journal of Infrastructure
Systems, 2005. 11(1): p. 51-60.
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doc_721775218.pdf
Information Technology perspective optimizing your costs is about spending wisely, judging where you cut and where you invest in terms of the impact on the business.
Bridge Life Cycle Cost
Optimization
Analysis, Evaluation, & Implementation
MOHAMMED ABED EL-FATAH SAFI
Master of Science Thesis
Stockholm, Sweden 2009
ii
KTH Architecture and
the Built Environment
Bridge Life Cycle Cost Optimization
Analysis, Evaluation, & Implementation
MOHAMMED ABED EL-FATAH SAFI
TRITA-BKN. Master Thesis 278
Structural Design and Bridge, 2009
ISSN 1103-4297
ISRN KTH/BKN/EX-278-SE
iv
© Mohammed Abed El-Fattah Safi, 2009
Supervisor: Professor Håkan Sundquist
Co-supervisor: Dr. Hans-Åke Mattsson
Royal Institute of Technology (KTH)
Department of Civil and Architectural Engineering
Division of Structural Design and Bridges
Stockholm, Sweden, 2009
Cover photo: Svinesund bridge between Sweden and Norway - right is Sweden, left is Norway.
i
PREFACE
This master thesis is devoted as a research study within ETSI project. ETSI project is contributed
between three Nordic countries, Sweden, Norway, and Finland. The main goals of the ETSI project
are to develop a Nordic unified methodology and computer program for bridge LCC evaluation.
After thanking God for granting me the strength and the will to fulfill the targets of this research
study, I would like to express my sincere thanks and hopes to my darling home country (The
occupied Palestine/Gaza), my parents, and my family who have instilled in me the drive and
encouragement to complete this work.
I would like to express my sincere appreciation and gratitude to my supervisors, Prof. Håkan
Sundquist & Dr. Hans Åke Mattsson, for their invaluable guidance, patience, kindness, and
encouragement throughout the work of my master thesis. It has been great honor to work with them
and to learn from their experience.
I want here to greatly appreciate my previous degree supervisors in Egypt, Prof. Baher Abou Stait
& Dr. Ahmed Al-Laithy, for their invaluable guidance and assistants to join KTH.
Finally, I would also like to acknowledge and thank everybody that has contributed to my pleasant
time at KTH during my master studies.
Stockholm, Sweden, Jun 2009
Mohammed Safi
ii
- iii -
ABSTRACT
Decisions related to implementation of a bridge design proposal generally require that several
alternatives be considered. Many factors contribute to an agency’s decision to select a particular
proposal. Although the initial project costs may dominate this decision, initial agency costs,
however, tell only a part of the story.
Currently, almost only functional performance and conventional financial costing guides the design
of a new bridge. A new life cycle framework to integrate all bridge life cycle considerations like the
aesthetical and cultural value, and the environmental impact with the economic issues become very
essential for achieving sustainable infrastructure.
This research study demonstrates a unique methodology and present a new systematic way for
analysis, evaluation, and optimization of the bridge life cycle indicators. This study is presenting a
unique flexible system, integrating all of bridge life cycle issues, and making them measurable and
comparable like the bridge initial cost.
One of the main aims of bridge projects is to preserve the harmony of the scenery and the
surrounding context. Aesthetics is not something that can be added on at the end. For aesthetics to
be successful, it must first be considered as an integral part of the design. Basic bridge aesthetics
design guidelines were proposed, which intended to set down considerations and principles, which
help in eliminating the worst aspects of bridge design and encourage the best.
Based on this unique evaluation system, two computer programs were developed to facilitate the
usage, one for calculating the bridge user cost and one to evaluate the bridge aesthetical and
cultural value. The application of this integrated model to bridge design highlighted a critical
importance of using the life cycle modeling in order to enhance the sustainability of bridge
infrastructure systems.
Keywords: life cycle cost analysis, aesthetical and cultural value, user cost, life cycle assessment
- iv -
DENOMINATIONS AND ABBREVIATIONS
LCC Life cycle cost
LCCA Life cycle cost analysis
LCA Life cycle assessment
SRA Swedish Road Administration
Finnra Finnish Road Administration
BMS Bridge Management System
BaTMan Bridge and Tunnel Management System (SRA’s BMS since 2004)
C
AG
Corresponding Agency cost
C
USER
Corresponding User cost
C
RACV
Corresponding Relative Aesthetical and Cultural Value cost
C
REI
Corresponding Relative Environmental Impact cost
k
AES
Aesthetical and cultural coefficient
k
EI
Environmental impact coefficient
C
REI
Corresponding Relative Environmental Impact cost
T Travel time delay for one vehicle in case of work zone
ADT
t
Average daily traffic at time t
N
t
Number of days needed to perform the work at time t
C
F
Average cost per fatal deaths accident for the society
C
I
Average cost per serious injury accident for the society
w
T
Hourly time value for one truck
w
p
Hourly time value for one passenger care
O
T
Average hourly operating cost for one truck including its goods operation
O
P
Average hourly operating cost for one passenger care
A
n
Bridge accident rates during the normal condition
A
a
Bridge accident rates during the work activities
- v -
CONTENTS
PREFACE v
ABSTRACT v
DENOMINATIONS AND ABBREVIATIONS v
1. INTRODUCTION ................................................................................. 1
1.1 General Background .................................................................................................1
1.2 Objective ....................................................................................................................1
1.3 Definitions..................................................................................................................1
1.4 Terminology...............................................................................................................2
2. AGENCY COST.................................................................................... 4
2.1 Bridge LCC Classification Scheme..........................................................................4
2.2 Costs by the Entity that Bears the Cost (Level 1) ...................................................4
2.2.1 Agency Costs ..........................................................................................................4
2.2.2 User Costs ...............................................................................................................4
2.2.3 Society Costs or Third-Party Costs.........................................................................5
2.3 Costs by LCC Category (Level 2).............................................................................5
2.3.1 Investment Cost (Purchasing, Construction, & Installation) ..................................6
2.3.2 Operation & Maintenance.......................................................................................6
2.3.3 Inspection................................................................................................................7
2.3.4 Repair/Rehabilitation & Replacement ....................................................................8
2.3.5 End of life Management (Demolition and Landscaping) .......................................9
2.4 Costs by Elemental Breakdown (Level 3) ...............................................................9
2.4.1 Elemental Costs ......................................................................................................9
2.4.2 Non-Elemental Costs ............................................................................................10
2.5 Life-Cycle Cost Analysis Approach........................................................................11
2.5.1 Integrated Life-Cycle Cost Analysis Approach....................................................11
2.5.2 Steps in Life-Cycle Cost Analysis ........................................................................12
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2.5.3 Economic Analysis Technique............................................................................. 12
3. BRIDGE USER COST........................................................................ 14
3.1 Introduction............................................................................................................. 14
3.1.1 Definition.............................................................................................................. 14
3.1.2 Background........................................................................................................... 14
3.1.3 Objective............................................................................................................... 14
3.2 Bridge User Cost Components .............................................................................. 15
3.2.1 Traffic Delay Cost (TDC) .................................................................................... 15
3.2.2 Vehicle Operation Cost (VOC) ............................................................................ 16
3.2.3 Accident Cost (AC) .............................................................................................. 17
3.2.4 Failure cost (FC)................................................................................................... 18
3.3 Sources of the Traffic Delay on the Bridge........................................................... 19
3.4 Work Zone and Traffic Flow Condition Relationship ......................................... 19
3.4.1 Work Zone Definition .......................................................................................... 20
3.4.2 Causes of the Traffic Delay at the Work Zone..................................................... 20
3.4.3 Work Zone Construction Window....................................................................... 20
3.4.4 Work Zone & Traffic Flow Conditions................................................................ 21
3.4.5 Work Zone Duration (Nt)..................................................................................... 27
3.5 Traffic Characteristics ............................................................................................ 28
3.5.1 Vehicle Classification........................................................................................... 28
3.5.2 Traffic Growth Rate ............................................................................................. 29
3.5.3 Traffic Control Plan (TCP)................................................................................... 29
3.5.4 Bridge Traffic Capacity........................................................................................ 31
3.6 Developed (BUC) Computer program & Practical Example.............................. 32
3.6.1 Practical Example................................................................................................. 32
3.6.2 Application using the developed computer program............................................ 32
3.6.3 Assumptions Window.......................................................................................... 33
3.6.4 Working Tasks Activation Window..................................................................... 33
3.6.5 Calculation Sheets ................................................................................................ 34
3.6.6 Results Window.................................................................................................... 36
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4. BRIDGE AESTHETICAL AND CULTURAL VALUE ................... 37
4.1 Introduction.............................................................................................................37
4.1.1 Background...........................................................................................................37
4.1.2 Objective...............................................................................................................37
4.2 Issues to be Considered..........................................................................................37
4.2.1 Bridge site classification.......................................................................................38
4.2.2 Cost and aesthetics can be complementary...........................................................38
4.2.3 Corresponding acceptable additional costs...........................................................39
4.3 Bridge Aesthetics Design Guidelines ....................................................................39
4.3.1 Sensitivity of the bridge type to the context and simplicity..................................39
4.3.2 The bridge form as a whole ..................................................................................41
4.3.3 The bridge Parts ....................................................................................................42
4.4 Unique Evaluation System.....................................................................................47
4.4.1 Body of the system................................................................................................47
4.4.2 Numerical values for p
i
and a ...............................................................................48
4.4.3 Bridge site classes.................................................................................................49
4.4.4 Recommended considered evaluation items.........................................................49
4.5 Practical Application and Testing..........................................................................50
4.5.1 The case background.............................................................................................50
4.5.2 The considered design proposals ..........................................................................51
4.5.3 The evaluation process..........................................................................................58
4.6 Developed Computer Program...............................................................................61
4.6.1 Introduction...........................................................................................................62
4.6.2 Working steps description.....................................................................................63
4.6.3 Example ................................................................................................................63
4.6.4 Practical use of the program.................................................................................65
5. BRIDGE ENVIRONMENTAL IMPACT.......................................... 66
5.1 Introduction.............................................................................................................66
5.2 Issued to be Considered..........................................................................................66
5.2.1 Project development stages and considerations....................................................66
- viii -
5.2.2 Toxics Classification ............................................................................................ 67
5.2.3 Toxics categories weighting impacts.................................................................... 67
5.2.4 Life cycle assessment (LCA)................................................................................ 68
5.3 Presentation of Previous Studies............................................................................ 68
5.4 Case study................................................................................................................ 70
5.4.1 Total weighted results........................................................................................... 70
5.4.2 Result per bridge and category............................................................................. 71
5.4.3 Impact per m
2
surface area of the bridge.............................................................. 71
6. SUMMARY.......................................................................................... 72
6.1 Conclusion and Discussion.................................................................................... 72
6.2 Recommendation and Further Research .............................................................. 72
BIBLIOGRAPHY.......................................................................................... 73
- 1 -
1. INTRODUCTION
1.1 General Background
Decisions related to implementation of a transportation improvement generally require that several
alternatives be considered. Many factors contribute to an agency’s decision to select a particular
option, although initial project costs may dominate this decision. Initial agency costs, however, tell
only part of the story.
The idea behind this study is that, bridges investment decisions should consider all of the costs and
considerations incurred during the period over which the alternatives are being compared. Bridges
are required to provide service for many years. The ability of a bridge to provide service over time
is predicated on its being maintained appropriately by the agency. Thus the investment decision
should consider not only the initial activity that creates a public good, but also all future activities
that will be required to keep that investment available to the public. It is important to note that the
lowest agency cost option may not necessarily be implemented when other considerations such as
aesthetical and cultural value, user cost, and environmental concerns are taken into account.
1.2 Objective
This study was designed firstly to expose the principles of bridge life cycle cost (BLCC) and
identify all of relevant affected parameters, secondly to separately focus on each life cycle
consideration and deeply illustrate the methodology of assessing its impacts on the whole BLCC.
The most important part of this study is the unique systematic way of converting all of the
theoretical data and parameters to a simple numerical calculations system which is relating the
aesthetical and cultural values, and the environmental impact with the other important aspects of
bridge like functionality, economics and techniques. When doing so, facilitate the implementation
of the optimization process.
The final goal is to create a simple compromise computer program, which is based on these data
and parameters and providing a simple optimization process to help the design makers to chose the
optimum alternative.
1.3 Definitions
Life Cycle Cost (LCC):
Technique which enables comparative cost assessments to be made over a specified period of time,
taking into account all relevant economic factors both in terms of initial capital costs and future
operational costs. In particular, it is an economic assessment considering all projected relevant cost
flows over a period of analysis expressed in monetary value. Where the term uses initial capital
letters it can be defined as the present value of the total cost of an asset over the period of analysis.
Life-Cycle Cost Analysis (LCCA):
LCCA is a cost-centric approach used to select the most cost-effective alternative that accomplishes
a preselected project at a specific level of benefits that is assumed to be equal among project
alternatives being considered. All of the relevant costs that occur throughout the life of an
alternative, not simply the original expenditures, are included.
- 2 -
Benefit-Cost Analysis (BCA):
BCA is the appropriate tool to use when design alternatives will not yield equal benefits, such as
when unlike projects are being compared or when a decision-maker is considering whether or not to
undertake a project. The elements typically included in LCCA and BCA are listed below.
Differences between (LCCA) and (BCA):
The agency that uses LCCA has already decided to undertake a project or improvement and is
seeking to determine the most cost-effective means to accomplish the project’s objectives.
LCCA is appropriately applied only to compare project implementation alternatives that would
yield the same level of service and benefits to the project user at any specific volume of traffic.
Unlike LCCA, BCA considers the benefits of an improvement as well as its costs and therefore can
be used to compare design alternatives that do not yield identical benefits (e.g., bridge replacement
alternatives that vary in the level of traffic they can accommodate), as well as to compare projects
that accomplish different objectives (a road realignment versus a widening project). Moreover,
BCA can be used to determine whether or not a project should be undertaken at all (i.e., whether
the project’s life-cycle benefits will exceed its life-cycle costs).
Life Cycle Assessment (LCA):
Tool for identifying and evaluating the environmental aspects of products and services from the
“cradle to the grave”: from the extraction of resource inputs to the eventual disposal of the product
or its waste. Life Cycle Assessment LCA is for assessing the total environmental impact associated
with a product's manufacture, use and disposal and with all actions in relation to the construction
and use of a building or other constructed facilities. LCA does not address economic or societal
aspects!
1.4 Terminology
Figure 1:1 Bridge breakdown components titles
- 3 -
Table 1:1 Bridge breakdown components name
Superstructure :
The part of structure which
supports traffic (include deck
, slab, and girders)
Deck :
bridge floor directly
carrying traffic loads
Hunching :
Increase in the depth of a continuous beam at the point
of support to withstand the increased moment of
bending on the beam.
Transition pier
Pier separating
different
superstructure types
Substructure
That part of the structure, i.e.
piers and abutments, which
supports the superstructure and
transfers load to the
foundations
Bearing
A component which transmits
forces from that par t to
another part
Abutment
The part of the structure
which supports the
superstructure at its
extremities and retains
earth works.
Pier Cap / Headstock :
A component which transfers
loads from the multiple girders
to the pier.
Safety / throw screen :
protective fence to deter the
launching of objects from the
bridge onto the highway
below
Pedestrian barrier
Traffic barrier :
Parapet – low protective
concrete wall at edge of
bridge deck.
- 4 -
2. AGENCY COST
2.1 Bridge LCC Classification Scheme
There are two primary reasons for establishing a life-cycle cost classification or taxonomy when
evaluating bridges. First, the classification insures that all costs associated with the project are
taken into account. Second, the classification scheme allows for a detailed, consistent breakdown of
the life-cycle cost and net savings estimates at several levels so that a clear picture can be had of the
respective cost differences between material/design alternatives.
The third benefit of this life-cycle cost classification is that, actual construction costs classified by
the same structural elements can be used to compile historical unit cost data on bridge element
costs to be used in future life-cycle cost analyses.
2.2 Costs by the Entity that Bears the Cost (Level 1)
In this level, the costs can be divided as shown in Figure 2:1 below, and will discuss in he
following subsections.
Figure 2:1 Cost by the Entity that Bears the Cost (Level 1)
2.2.1 Agency Costs
Agency costs are all costs incurred by the project’s owner or agent over the study period. These
include but are not limited to design costs, capital costs, insurance, utilities, and servicing and
repair of the facility. Agency costs are relatively easy to estimate for conventional material/designs
since historical data on similar projects reveal these costs, will discuss it later in this chapter.
2.2.2 User Costs
Bridge LCC
Agency cost User Cost Society Cost
Aesthetical &
Cultural Value
Environmental
Impact (LCA)
- 5 -
User costs accrue to the direct users of the project. For example, bridge construction often causes
congestion and long delays for private and commercial traffic. New bridge construction impacts
traffic on the highway over which it passes. Maintenance and repair of an existing bridge, along
with the rerouting of traffic, can impact drivers’ personal time, as well as the operating cost of
vehicles sitting in traffic. Accidents, involving harm to both vehicles and human life, tend to
increase in road work areas; will deeply discuss it later in this chapter (3).
2.2.3 Society Costs or Third-Party Costs
Third-party or spillover costs are all costs incurred by entities who are neither the agency/owners
themselves nor direct users of the project. One example is the lost sales for a business establishment
whose customer access has been impeded by construction of the project, or whose business
property has been lost through the exercise of eminent domain. A second example is cost to humans
and the environment from a construction process that pollutes the water, land, or atmosphere. These
costs can be subdivided into two main categories:
Bridge Aesthetical & Cultural Value (ACV)
Some projects have exceeded all cost estimates but still it has been possible to fulfill them with
success. One of the main aims of bridge projects is to preserve the harmony of the scenery.
Location of a bridge, cultural values of the surroundings, landscape and the viewpoints of local
people have influence on the goals that are set to a bridge in the beginning of a project. Bridges are
often seen more or less as sculptures and icons which the citizens may relate with the soul of the
city. This atmosphere and the will to identify the town and its values with an icon may motivate for
bold and spectacular solutions.
So, absolutely there is a hidden value for the external appearance and the beauty of the bridge, it
should be considered during the design and in the LCCA process. This value is called the ACV.
It is not the intention to provide a formula for good design. Rather it is the intention to set down
considerations and principles, which will help, eliminate the worst aspects of bridge design and
encourage the best, will deeply discuss it later in this chapter (4).
Bridge Environmental Impact (LCA)
Environmental impact categories evaluated include energy and material resource consumption, air
and water pollutant emissions, solid waste generation, energy use, fuel consumption, and emissions
for the traffic. Life cycle assessment is an analytical technique for evaluating the full environmental
burdens and impacts associated with a product system, will deeply discuss it later in this chapter
(5).
2.3 Costs by LCC Category (Level 2)
Level 2 groups the costs according to the life-cycle categories which, in KTH we agreed to classify
them ascending by there occurrence during the bridge life cycle, with these proposed titles as
follow:
Investment Cost (Purchasing, Construction, & Installation)
Operation & Maintenance Cost
- 6 -
Inspection Cost
Repair/Rehabilitation & Replacement Cost
End of life Management Cost (Demolition and Landscaping)
Historical agency data are only one mechanism that may be used to feed LCCA input needs. The
expert opinion of senior agency staff members can also provide a wealth of information for
investment analyses, as can research conducted by industry and government. Still, the agency will
have to devote resources toward the development and validation of data sources for LCCA inputs,
as well as toward learning how to use those sources.
2.3.1 Investment Cost (Purchasing, Construction, & Installation)
An example of historical agency data for bridge investment costs can be as shown in following
table:
Table 2:1 Investment Feedbacks and Recommendation
2.3.2 Operation & Maintenance
Operation: - The preservation and upkeep of a structure, including all its appurtenances, in its
original condition (or as subsequently improved). Maintenance includes any activity intended to
“maintain” an existing condition or to prevent deterioration. Examples include: cleaning,
lubricating, painting, and application of protective systems.
Maintenance: - The minor repair and preventative maintenance activities necessary to maintain a
satisfactory and efficient structure, usually prescheduled maintenance and repair activities.
An example of historical agency data for bridge operation and maintenance costs can be as shown
in following table:
Table 2:2 Operation & Maintenance Feedbacks and Recommendation
- 7 -
2.3.3 Inspection
The main purpose of the inspections is to ensure that the safety and traffic ability of the bridges
meet the requirements; the inspections reveal the physical and functional condition thus providing
the basis for an efficient and economical bridge management. The bridge inspections in Sweden are
since 1987 divided into three types, according to the nature of their aim, scope and frequency. They
are:
General inspection
Major inspection
Special inspection
General inspection: - The aim of is to follow up the assessed damage during earlier inspections,
detect and assess new damage, and detect if the contracted maintenance work has been properly
performed. Every structural part of the bridge together and their included elements have to be
visually inspected. Structural parts under water are excluded. There is no demand on hand-close
investigation unless new damage is detected. General inspection is a simpler inspection compared
to the major inspection. The scope of the general inspection is to check the recorded damage from
previous major inspections and check if the assessed development of these was correct. If new
damages are detected, they will be recorded and assessed according to current rules. General
inspection has to be performed on bridges with a theoretical span larger than 2,0 meters. Smaller
bridges are normally exempted from this inspection type. The time interval between two general
inspections is maximum three years. The personnel performing this inspection type have to posses
the same competence as the inspectors performing major inspections.
Major inspection: - The most important inspection type performed on the Swedish road bridges.
The scope of this inspection type is to detect and asses damages and defects which can affect the
designed function or the traffic safety, both in the short and the long run (within 10 years). Another
aim is to detect even minor damage or defects that, if not attended to, can cause increased
maintenance or repair costs within a 10-year period. Every structural part and their in-going
elements, which are within hand reach, have to be investigated.
During this inspection, even the structural parts located under the water surface have to be closely
inspected by qualified divers. Even adjoining parts of the bridge such as road embankments, slopes,
abutment ends, fill revetment and fenders have to be inspected. If the inspected bridge contains
mechanical or electrical equipment, such as movable bridges, these parts will also be subject to
close inspection. The inspection has to be done hand-close. Special inspection equipment, such as a
bridge-lift, will allow a close look under the bridge deck, a structural part difficult to inspect
otherwise.
This inspection type requires that a series of physical measurements have to be performed. Such
measurements are made to determine for example the real bottom profile (erosion risk), chloride
content and carbonization of concrete, measurements of the level of corrosion of the reinforcement
bars and cracking. The major inspection has to be carried out at least every sixth year. The demands
on the bridge inspectors performing these are high.
Special inspection: -For more information see BaTMan (2000) or the Swedish Bridge inspection
An example of historical agency data for bridge inspection costs can be as shown in following
table:
- 8 -
Table 2:3 Inspection Feedbacks and Recommendation
2.3.4 Repair/Rehabilitation & Replacement
Repair: - The restoration of a structure, including all its appurtenances, to its original condition (or
as subsequently improved) insofar as practicable. Repair includes any activity intended to correct
the affects of material deterioration by restoring or replacing in-kind any damaged member.
Rehabilitation: - The improvement or betterment of a structure, including all its appurtenances, to
a condition which meets or exceeds current design standards.
Examples of rehabilitation include, widening a bridge to meet lane/shoulder width requirements,
raising a bridge to meet clearance requirements, replacement of substandard bridge rails,
strengthening a bridge to increase load carrying capacity to accepted limits, replacement of deck,
rehabilitation of deck, and rehabilitation of superstructure.
Replacement: - The erection of a new structure at or near an existing structure, with the new
structure(s) intended to receive the service loads from the existing structure which is eventually
abandoned, relocated, or demolished.
An example of historical agency data for bridge repair/rehabilitation & replacement costs can be as
shown in following table:
Table 2:4 Repair/Rehabilitation & Replacement Feedbacks and Recommendation
- 9 -
2.3.5 End of life Management (Demolition and Landscaping)
An example of historical agency data for bridge demolition and landscaping costs can be as shown
in following table:
Table 2:5 Ends of Life Management Feedbacks and Recommendation
2.4 Costs by Elemental Breakdown (Level 3)
The third level of classification organizes costs (1) by specific functional element of the structure or
facility, (2) by activities not assignable to functional elements (e.g., overhead). Parts (2) is the
traditional “elements” cost. We add new-technology introduction costs to measure the unique costs
of using a new material. Schematically Figure 2:2 below will introduce this level.
Figure 2:2 Costs by Elemental Breakdown (Level 3)
2.4.1 Elemental Costs
Elements are major components of the project’s structure, and are sometimes referred to as
component systems or assemblies. Elements common to bridges are superstructure, substructure,
and approach. Each element performs a given function regardless of the materials used, design
specified, or method of construction employed.
Individual cost estimates at the elemental level (e.g., $/square meter to furnish and install a concrete
deck) are most useful in the pre-design stage when a variety of material/design combinations are
being considered. This is the stage at which large net savings can be achieved by making
economically optimal material/design choices as shown in Figure 2:3.
Agency cost
Non-Elemental
Costs
Elemental Costs
Studies,Planning,Design,&
Management
Site Facilitate
Mobilization Camping
Traffic Organization &
Safety Control
Overheads
Introduction of New
Technology
- 10 -
2.4.2 Non-Elemental Costs
Non-elemental costs are all costs that cannot be attributed to specific functional elements of the
project. A common example of a non-elemental agency cost is overhead expenses; a non-elemental
third-party cost could be spillover costs. Because elemental cost categories are useful for generating
and updating historical unit cost measures, all project costs that are not truly elemental must be
excluded from these historical statistics and put in the non-elemental group. Schematically graph
compose these three levels can be as shown in Figure 2:4 below
1
0
0
%
Time
Planning
Design
Construction
Investment decision
Accumulated
consumption of
resources
Possibilities to
influence the final cost
Inauguration
L
C
C
/
C
o
n
s
t
r
u
c
t
i
o
n
c
o
s
t
Operation and
maintenance
Obs change of
time scale
Figure 2:3 Bridge Stages and the possibilities to influence the LCC
- 11 -
Figure 2:4 Bridge LCC Classification Levels
Notation for bridge main structures and its elements are presented in Table 2:6; see also Figure 1:1,
and Table 1:1.
Table 2:6 Bridge Component Breakdown
2.5 Life-Cycle Cost Analysis Approach
2.5.1 Integrated Life-Cycle Cost Analysis Approach
The term life cycle cost (LCC) is not used consistently. The more traditional view of LCC evaluates
costs incurred by government agencies all through the value chain (from raw material acquisition to
end of life). Such costs are termed “agency costs.” Recently, efforts have been made to broaden this
definition to be more inclusive of other costs associated with construction projects. In particular,
several studies, using a more holistic LCC approach, have been conducted with the goal of
determining agency costs as well as user costs
An integrated life cycle assessment, aesthetical and cultural value, and cost model was developed in
this master thesis to evaluate the bridge sustainability, and compare alternative materials and
designs using environmental, economic and social indicators where, the bridge LCC is equal to:
- 12 -
REI RACV USER AG C C C C LCC + + + =
Where:
o C
AG
Is the corresponding Agency cost.
o C
USER
Is the corresponding User cost.
o C
RACV
Is the corresponding Relative Aesthetical and Cultural Value cost.
o C
REI
Is the corresponding Relative Environmental Impact cost.
Where:
Here C
AG
is the Agency cost obtained by cost calculation considering the construction, repair,
maintenance and demolishing costs of the bridge from its whole lifetime.
The Relative Aesthetical and Cultural Value cost C
RACV
of a bridge, is then obtained by equation:
AG C k C AES RACV =
o k
AES
Is the aesthetical and cultural coefficient. Range from +0,30 To -0,30
Finally, the Relative Environmental Impact cost C
REI
of a bridge, is then obtained by equation:
AG REI C k C EI =
o k
EI
Is the environmental impact coefficient. Range from 0,0 To +0,20
Consequently, the system described above enables comparison between different design
proposals, existing bridges and bridge types as well as evaluation of even different construction
methods.
2.5.2 Steps in Life-Cycle Cost Analysis
Define the project objective and minimum performance requirements.
Identify the alternatives for achieving the objective.
Establish the basic assumptions for the analysis.
Identify, estimate, and determine the timing of all relevant costs.
Compute the life-cycle cost of each alternative
Perform sensitivity analysis by reusing different assumptions
Compare the alternatives’ life-cycle costs
Consider other project effects
Select the best alternative.
For LCCA to yield valid results, each project alternative considered must provide the same level of
service or utility for a specific, given volume of traffic. In the event that the alternatives yield
different levels of service or utility, then benefit-cost analysis (BCA), not LCCA, would be the
appropriate decision tool. LCCA provides a comprehensive means to select among two or more
alternatives to accomplish the project.
2.5.3 Economic Analysis Technique
- 13 -
The time value of money is germane to LCCA because costs included in the analysis are incurred at
varying points in time. Figure 2:5 show an example of the bridge LCC cash flow. For LCCA, costs
occasioned at different times must be converted to their value at a common point in time. It's
recommended to use the present value (PV) approach (also known as “present worth”), the formula
to discount future constant value costs to present value is:
( )
n
r
+
× =
1
1
Value Future Value Present
Where:
- r Is the real discount rate
- n Is the number of years in the future when the cost will be incurred.
Figure 2:5 LCC Cash Flow Example
For LCCA to be performed in a right way, the proposals on, how to design the bridge should
contain a lot of documents describing the bridge from a lot of different aspects, Table 2:7 present
these documents as follow.
Table 2:7 Documents to be submit with the bridge design proposal
A) Descriptions B) Design calculations
• General description of the
proposal and
design concept
• Technical description.
• Description of the construction
process.
• Description on how to inspect and
maintain the bridge
• Rough statical and dynamical analyses of
the bridge
• A lot of other important factors that affect
the bridge, as for instance wind, stability,
vibration, stiffness, etc
• Rough estimated cost calculations
• LCC-calculation.
C) Drawings D) Perspective/Photomontage/Model
• Plan.
• Elevation.
• Special elevations in a smaller
scale 1:100.
• Type sections.
• Important details.
• Photomontage of the bridge on four
delivered pictures.
• Model in scale 1:500.
- 14 -
3. BRIDGE USER COST
3.1 Introduction
3.1.1 Definition
Bridge user costs are costs incurred by users of the bridge as a result of deteriorated conditions on
the bridge, such as a narrow width, low load capacity, or low vertical clearance which are resulting
from construction, maintenance, inspection, rehabilitation, and demolition activities, leading to an
increase in the vehicles trip time which is translated into user delay costs, additional vehicle
operating costs and increase risk and accident costs.
3.1.2 Background
The bridges are aging, and the agencies are focusing on maintenance and rehabilitation of existing
bridges infrastructure to a greater extent than ever before. Work on existing bridges, whether its
purpose is to rehabilitate or to add capacity, requires the use of work zones to protect bridge users
and construction workers. By reducing capacity, work zones often cause user costs to rise due to
increases in travel time, vehicle operating costs, and possibly the number and severity of crashes.
User costs contribute significantly to the total life cycle cost and should be considered in the
analysis of bridge networks, designers should consider road user costs when determining the most
appropriate construction staging and final design. A study by the Florida Department of
Transportation (Thompson et al., 1999) estimated that user costs may exceed the repair costs by a
factor of 5 or more.
Bridge user costs are not direct costs, but they do directly affect the public it serves. For example,
the construction of a $1 million full width shoulder to reduce bridge user costs by $2 million
increases agency costs to reduce road user costs.
3.1.3 Objective
This chapter will familiarize the analyst with work zone and traffic characteristics, explain the
possible related bridge user cost components, and provide a step by step procedure for
computations considering all traffic condition related aspects.
Based on this procedures and information, develop a systematic computer program to simplify and
facilitate the quantification and then, enable to determine the cost effectiveness of various
alternatives and optimize the work-zone strategies in order to minimize user costs.
- 15 -
3.2 Bridge User Cost Components
Before addressing bridge user cost calculation procedures, it is helpful to understand the bridge user
cost components. Figure 3:1 illustrate the user cost components and their appearance events.
Figure 3:1 Bridge user cost components and appearance events
Bridge user cost during a work zone are usually evaluated with respect to the traffic delay costs
(TDC), the additional vehicle operating costs (VOC) to cross the work zone, the related-accident-
costs (AC), and the risk of failure cost (FC). The following equation is used to determine bridge
user cost during a work zone.
FC AC VOC TDC Cost User Bridge + + + =
The costs should be calculated to present value and added up for all foreseen maintenance and
repair works for the studied time interval T
E
.
3.2.1 Traffic Delay Cost (TDC)
The traffic delay cost (TDC) results from the increase in travel time through the work zone due to
speed reductions, congestion delays, or increased distance as a result of a detour. Therefore, the
TDC is calculated based on the difference between the time taken to cross the bridge and the time
taken to finish the detour or the work zone.
) 1 (
1
) ) 1 ( (
0
?
=
+
? + × × × =
E
P T T T
T
t
t
t t
r
N ADT T TDC w r w r
Where:-
??? , , = = ? = WZ
o
WZ T
v
L
T T T T o o
- T is the travel time delay for one vehicle in case of work zone, (hour),
- ADT
t
is the average daily traffic at time t, measured in number of, (vehicle/day),
Bridge User Cost
Construction & Installation
Operation & Maintenance
Inspection Repair, Replacement &
Rehabilitation
Traffic Delay Cost Vehicle operation Cost Accident Cost Failure cost
Demolition & landscaping
- 16 -
- N
t
is the number of days needed to perform the work at time t, (Day),
- r
T
is the percentage of trucks from all AVD,
- w
T
is the hourly time value for one truck,
- w
p
is the hourly time value for one passenger care,
- T
WZ
is the time taken to finish the detour or to cross the work zone, (hour),
- T
o
is the taken to cross the bridge during the normal flow conditions, (hour),
- L is the affected bridge length, (km),
- vo is the traffic speed in the normal traffic flow condition, (km/hr),
- v
WZ
is the work zone speed, (km/hr),
- TE is the bridge expected life span.
The duration travel delay time in case of work zone (T) is strongly associated with the traffic flow
condition, the hourly traffic distribution, and work zone construction window; we will do deeply in
this matter in the work zone and traffic characteristics subsection in this chapter.
The value of w
The value of one hour of travel time per vehicle is assumed to be equal to:
o $8/hr/veh regardless of vehicle type; The Federal Highway Administration (1989)
o $25/hr/veh. regardless of vehicle type; He et al. (1997)
o $12/hr/veh. regardless of vehicle type; Schonfeld (2003)
o Thoft-Christensen (2006)
$ 11,38 - 11,58 for passenger cars.
$ 22,31 - 27,23 for trucks
Recommended value of w:
It should be equal to the average hourly wage for average employee in the considered country. The
argument for that is, because W is representing the value of delaying the vehicle driver one hour
instead of reaching his work at time. For example, in Sweden 2009 the average hourly wage is
equal to 120 SEK which is approximately equal to $14, this will be suitable for passenger cars, and
for other vehicles is equal to this value multiply by 2, regardless the number of persons inside the
vehicle, so the recommended value according to Sweden 2009:
$ 14,0 /hr for passenger cars.
$ 28,0/hr for other vehicles.
3.2.2 Vehicle Operation Cost (VOC)
VOC is an additional cost incurred by the bridge user, expressed as extra costs to operate the
vehicle additional time due to the traffic disturbances because of the work zone or detour. The
operating costs include fuel, engine oil, lubrication, maintenance, and depreciation.
) 1 (
1
) ) 1 ( ( OC
0
?
=
+
? + × × × =
E
P T T T
T
t
t
t t
r
O O N ADT T V r r
- 17 -
Where:-
Same parameters are used except for:
- O
T
is the average hourly operating cost for one truck including its goods operation,
- O
P
is the average hourly operating cost for one passenger care.
The value of O
The recommended value according to Sweden 2009:
$ 9,5/hr for passenger cars.
$ 21,5/hr for other vehicles.
3.2.3 Accident Cost (AC)
Background
AC is representing the costs of increasing the risk of crushes, health-care, and deaths which
resulting from the traffic disturbances due to work zone on the bridge.
Although bridge-related accidents represent only about 1.7% of all traffic accidents, the degree of
severity is estimated to be from 2 to 50 times the severity of general roadway traffic accidents. The
average number of peoples were killed in bridge related accidents was determined to be equal to
0.009 persons/accident (Abed-Al-Rahim and Johnston, 1991, 1993).
Computation method
Obviously its consequences appear when comparing two different types bridge structures, where
the risks for accidents and the safe maintainability are differs. The bridge accident costs during
work zone could be calculated as:
[ ]
) 1 (
1
) ( ) ( ) ( C
0
?
=
+
× + × × ? × × =
E
I I F F a n
T
t
t
t t
r
P C P C A A N ADT A
Where:-
Same parameters are used except for:
- A
n
The bridge accident rates during the normal condition, (Accident/Vehicle/L/day),
- A
a
The bridge accident rates during the work activities, (Accident/Vehicle/L/day),
- C
F
The average cost per fatal deaths accident for the society
- C
I
The average cost per serious injury accident for the society
- P
F
The average number of killed persons in bridge related accidents, which is
equal to 0,009 (Persons/Accident)
- P
I
The average number of injured persons (not killed) in bridge related accidents,
which is equal to 0,991 (Persons/Accident)
Value of average cost per accident
- 18 -
[ ] 33 , 1 ) 1 ( ) ( ) ( 783 , 0
05 , 0 033 , 0 073 , 0
? + × × × = WZ BL ADT NOACC
o Swedish Road Administration 2009
$1,500,000 for fatal deaths crush
$500,000 for serious injury crush
o United States of America FHWA
$1,240,000 for fatal deaths crush
$151,000 for serious injury crush
o $68,404 Soares (1999)
o Recommended value in this chapter
$1,500,000 for fatal deaths crush
$160,000 for serious injury crush
Bridge- related accident rate
Aded-Al-Rahim and Johnston (1991, 1993) proposed a model for calculating the risk of accidents
that considers the average daily traffic (ADT) and the bridge length, as follows:
Where:
- NOACC = The number of accidents per year,
- LB = The bridge length in (Feet)
- WZ = The work zone width, in (Feet), equal to zero during normal conditions
Comments & Recommendation
It is difficult to accurately quantify the work zone exposure rate (i.e. the length of the work zone
and the hours and days the work zone queues are in place). Further, the crash rate, while generally
higher in work zones than non-work zones, is still low enough that there may not be any crashes in
a given work zone because the exposure period is just too short to allow for statistically valid
results. Finally, the problem is compounded by the fact that work zones differ in the way they treat
maintenance of traffic. For example, some work zones use permanent barriers, while others use
cones or drums; some narrow the lanes, while others maintain lane width and shoulders, etc.
o While there is a limited amount of work zone crash data, the validity of the data used to
compute the crash rates is sometimes suspected.
3.2.4 Failure cost (FC)
- 19 -
There is a small risk for the total failure of a structure. To get the cost for failure one has to
calculate all costs (KH,j) for the failure, accidents, rebuilding, user delay costs and so on and then
multiply these costs with the probability for failure and with the appropriate present value factor
according to the formula
?
=
+
=
n
j
j
r
R K FC j j H
1
) 1 (
1
,
Rj is the probability for a specified failure coupled to KH,j. For normal bridges the probability of
failure is so small that the failure costs could be omitted in the analysis. The cost for serviceability
limit failure is discussed in Radoji?i? (1999), but actually the methods presented in the present
paper are a kind of statistically LCC-method given that the parameters for remedial actions are
considered random.
o Due to the limited availability of probability of failure data, the inclusion of the failure
costs as part of the Bridge user costs is not recommended.
3.3 Sources of the Traffic Delay on the Bridge
An example of historical agency data and feedbacks including recommended time required to
perform work activates are presented in Table 3:1 as follow:
Table 3:1 Work activities that affect the traffic
3.4 Work Zone and Traffic Flow Condition Relationship
- 20 -
3.4.1 Work Zone Definition
Work zone is defined as an area of a highway in which maintenance and construction operations
are taking place that impinge on the number of lanes available to traffic or affect the operation of
the traffic flowing. Work zones restrict traffic flow either by restraining the capacity of the bridge
or, by posting lower speed limits.
In order to calculate bridge work zone related user costs the characteristics of the work zone must
be defined. Work zone characteristics include such factors as work zone length, number and
capacity of lanes open, duration of lane closures, timing (hours of the day and days of the week) of
lane closures, posted speed, and the availability and traffic characteristics of alternative routes.
3.4.2 Causes of the Traffic Delay at the Work Zone
There are three sources of traffic delay at work zone:
o Speed reduction delay (moving delay),
o Congestion delay (stopping delay).
o Circuity delay (extra distance moving delay),
Speed-reduction delay: result from vehicles moving more slowly than the normal bridge speed.
Congestion delay: occurs when the hourly traffic volume is greater than the capacity of a work zone
for a significant period of time. In this case a queue forms, the queue decreases only during time
periods when the demand is less than the capacity.
Circuity delay: is a term used to describe the additional mileage that users travel, either voluntarily
or involuntarily, on a detour to avoid a bridge work zone or queue situation. Its usually take place
in the construction and in the major replacement activities when the bridge have to be closed.
3.4.3 Work Zone Construction Window
Bridge repair and rehabilitation window (time of day to do the work) traditionally occur at
nighttime because daytime closures cause unacceptable delays to weekday peak travel. However,
the disadvantage of having nighttime closures is that they may lead to lower work quality, longer
closure time and higher construction and traffic control plan costs. Four construction window
strategies are recommended:
o Nighttime shifts closure, from 7:00PM To 5:00AM,
o Fulltime closure, 24 Hour/Day.
o Weekend closure,
o Weekday closure.
Alternatively, combinations of the four construction windows are used some times.
Hourly traffic distribution
The effective procedure for quantifying speed reduction delay and is to convert the ADT into an
hourly volume, estimate the delay on an hourly basis, and cumulate the hourly delay into a daily
delay. Data related to the ADT and the hourly traffic distribution is often available from the
municipalities. As an illustration, Table 3.2 shows an example of hourly traffic distribution
- 21 -
(USDOT/FHWA, 1998) and provides a distribution factor (% ADT) for each hour of the day for
different highway types. Based on this distribution factor, the hourly traffic can be calculated as:
Hourly Traffic = ADT × Distribution Factor
Table 3:2 Example of Hourly Traffic Distribution (USDOT/FHWA, 1998)
Hour Distribution Factor(%ADT) Hour Distribution Factor(%ADT)
From To Interstate Other From To Interstate Other
0 1 1.70% 0.90% 12 13 5.70% 5.70%
1 2 1.40% 0.50% 13 14 5.90% 5.90%
2 3 1.30% 0.50% 14 15 6.30% 6.60%
3 4 1.30% 0.50% 15 16 6.90% 7.70%
4 5 1.40% 0.90% 16 17 7.20% 8.00%
5 6 2.10% 2.30% 17 18 6.60% 7.40%
6 7 3.70% 4.90% 18 19 5.30% 5.50%
7 8 4.90% 6.20% 19 20 4.40% 4.30%
8 9 4.90% 5.50% 20 21 3.80% 3.60%
9 10 5.20% 5.30% 21 22 3.40% 3.00%
10 11 5.50% 5.40% 22 23 2.90% 2.30%
11 12 5.80% 5.60% 23 24 2.40% 1.50%
3.4.4 Work Zone & Traffic Flow Conditions
The duration of work zone delay time is strongly associated with the traffic flow condition. Three
types of the traffic flow condition:
o Unrestricted flow conditions, where the traffic operates under “Base Case” situation
o Forced flow conditions, where traffic operates under “Queue” situation
o Circuity flow condition, where traffic is forced to utilize a detour
Unrestricted Flow Condition
Where the traffic volume is below the work zone capacity, all traffic that flows through the work
zone, must slow down while traveling through it and then accelerate back to normal operating
speed. The delay time components associated with the unrestricted flow condition are described in
the below figure.
Figure 3:2 The Delay Time Duration In Case of Unrestricted Flow Condition
- 22 -
3 2 1 T , , T T T
V
L
T T T T WZ
o
WZ o o + + = = ? =
Where:-
- T is the travel time delay, (hour),
- T
o
is the required to cross the affected bridge length (L) during the normal flow
conditions, (hour),
- T
1
is the time required to decelerate from the normal speed (V
0
) to the work zone
speed (V
WZ
), (hour),
- T
2
is the time required to cross the work zone driving by the posted work zone
speed (V
WZ
), (hour),
- T
3
is the time required to accelerate back from the work zone speed (V
WZ
), to the
normal speed (V
0
), (hour).
Parameters identification and valuation:
L
1
Is the minimum distance needed to decelerate from V
o
to V
wz
(m)
) ( 245
278 . 0
2 2
0
0 . 1
G f
V V
V t d d L
wz
r dec r
±
?
+ = + =
Where:
- d
r
The perception reaction distance (m)
- d
dec
The minimum deceleration distance (m)
- V
0
,V
wz
The normal speed and work zone speed (km/h)
- t
r
The perception/reaction time(Sec.), average equal to 2,5 sec.
- f The AASHTO stopping friction coefficient (dimensionless), Table 3:3
- G The roadway grade (dimensionless), assume it equal to zero(horizontal bridge)
Table 3.3 Design speed and the corresponding friction coefficient (USDOT/FHWA, 1998)
Design Speed
(km/h)
30 40 50 60 70 80 90 100 110 120
Coefficient of
Skidding Friction(f)
0.4 0.38 0.35 0.33 0.31 0.3 0.3 0.29 0.28 0.28
T
1
Is the time needed to decelerate from V
o
to V
wz
(hr)
) (
. 2
0
1
wz
dec
r
V V
d
t T
+
+ =
L
0
Is the optimum work zone length, which is the suitable length to fit the work
equipments, workers, and the working area itself. Of coarse its depend on the type of the
working activities, the bridge length, and the technology used in the work. But we can say
here, the minimum acceptable safe working length should not be less than 150 m regardless
the bridge length, the recommended length can be obtained from the following table:
- 23 -
Table 3:4 Bridge length and the recommended work zone length
Bridge Length (m) <150 150 - 500 >500
Recommended optimum work zone length L0 (m) 150 200 300
For simplification consider the average length regardless the bridge length is equal to 200 m.
T
2
Is the time required to cross the work zone driving by V
WZ
, (hour),
wz V
L
T
0
2 =
L
3
Is the minimum distance needed to accelerate back from V
wz
to V
0
2
) (
2
3
3 3
T a
T V L wz + =
Where:
- a is an average vehicle acceleration rate which is equal to 2,28 m/Sec
2
(29458,8km/hr)
T
3
Is the time required to accelerate back from V
WZ
to V
0
, (hr).
a
V V
T
wz ?
=
0
3
As an application for the above mentioned system and formulas, we can relate the travel
time delay of the bridge work zone to bridge normal speed as shown in Table 3:5.
Table 3:5 Traffic delay time due to unrestricted flow condition
Forced Flow Condition
Where the traffic volume exceeds the work zone capacity, traffic flow breaks down and a queue of
vehicles develops as shown in Figure 3.4. Once a queue develops, all approaching vehicles must
stop at the approach to the work zone and creep through the length of the physical queue under
forced flow conditions at significantly reduced speeds, it is common for queues to develop in the
- 24 -
morning peak traffic period, dissipate, and then redevelop in the afternoon peak traffic period. The
delay time components associated with the forced flow condition are described in the below figure.
Figure 3:3 The Delay Time Duration In Case of Forced Flow Condition
4 3 2 1 T , , T T T T T
V
L
T T T T q WZ
o
WZ o o + + + + = = ? =
Where:-
- T is the travel time delay, (hour),
- T
o
is the required to cross the affected bridge length (L) during the normal flow
conditions, (hour),
- T
1
is the time required to stop the vehicle from the normal speed (V
0
), (hour),
- T
q
is the time required to creep through the queue by the queue speed (V
q
), (hour),
- T
2
is the time required to creep through the work zone by firs step, accelerating from
The queue speed (V
q
) the work zone speed(V
WZ
), (hour),
- T
3
is the time required to creep through the work zone by second step, driving by
work zone speed(V
WZ
), (hour),
- T
4
is the time required to accelerate back from the work zone speed (V
WZ
), to the
normal speed (V
0
), (hour).
Parameters identification and valuation:
L
1
Is the minimum stopping sight distance needed to decelerate from V
o
to 0 ,
(m)
) ( 245
278 . 0
2
0
0 1
G f
V
V t d d L r b r
±
+ = + =
Where:
- d
r
The perception reaction distance (m)
- d
b
The minimum breaking distance (m)
- V
0
The normal speed, (km/h)
- t
r
The perception/reaction time (Sec.), average equal to 2,5 sec.
- f The AASHTO stopping friction coefficient (dimensionless)
- G The roadway grade (dimensionless), assume it equal to zero(horizontal bridge)
- 25 -
T
1
Is the time needed to stoop the vehicle (Sec.)
0
1
2
V
d
t T
b
r + =
L
q
Is the average length of the queue ,
(m)
(AQV) (AVL) Lq /Lan vehicles queued Average lenght vehicle Average × =
The average vehicle length includes an assumed vehicle length (VL) and the space between
vehicles. The mixed flow VL is 7,62 m. The space between vehicles is computed as one VL for
every 16 km/h of the average queue velocity (V
q
). The minimum average vehicle length is 12,2 m.
¦
)
¦
`
¹
¦
¹
¦
´
¦
+
=
m ,
V
, ,
AVL
q
2 12
)
16
( 62 7 62 7
of max.
V/C Ratio
The volume to capacity (V/C) ratio is calculated by dividing capacity of the bridge in case of work
zone by the normal capacity of the bridge. The average queue velocity (V
q
) is determined by using
V/C Ratio and the following graph.
0
5
10
15
20
25
30
35
40
45
0 0.2 0.4 0.6 0.8 1
V/C Ratio
A
v
e
r
a
g
e
Q
u
e
u
e
V
e
l
o
c
i
t
y
V
q
(
k
m
/
h
r
)
Figure 3:4 Average Queue Velocity Vq versus V/C Ratio sourc
NCHRP133)The formula for this graph can be utilities in the following equation.
0057 0 48 21 18 19
2
, (V/C) , (V/C) , Vq + + =
According to this, the average vehicle length can be calculated as show in Table 3:6.
- 26 -
Table 3:6 Average vehicle length according to bridge configuration
T
q
Is the time required to creep through the queue (Sec.)
q
q
q
V
L
T =
L
2
Is the minimum distance needed to accelerate from speed equal to V
q
to V
WZ
2
) (
2
2
2 2
T a
T V L q + =
T
2
Is the time required to accelerate from V
q
to V
WZ
through the work zone, (hour),
a
V V
T
q wz ?
= 2
Where:
- a is an average vehicle acceleration rate which is equal to 2,28 m/Sec
2
(29458,8km/hr)
L
3
Is the remaining work zone length which is equal to L
o
-L
2
2 0 3 L L L ? =
T
3
Is the time required to creep through the work zone by driving with (V
WZ
), (hour),
wz V
L
T
3
2 =
L
4
Is the minimum distance accelerate back needed to from V
wz
to V
0
2
) (
2
4
4 4
T a
T V L wz + =
Where:
- a is an average vehicle acceleration rate which is equal to 2,28 m/Sec
2
(29458,8km/hr)
- 27 -
T
4
Is the time required to accelerate back from V
WZ
to V
0
,
a
V V
T
wz ?
=
0
4
Cricuity Flow Condition
Circuity is a term used to describe the additional distance that users travel, either voluntarily or
involuntarily, on a detour to avoid a highway work zone or because of the bridge closing situations.
For non-detour cases, it is assumed the traffic will remain on the bridge and travel the queue and/or
work zone situations. If a formal detour is established and traffic is forced to detour, the associated
cost components are described below.
D
D
D
o
WZ
V
L
T
V
L
T T T T o o = = ? = , ,
Where:-
- T is the travel time delay, (hour),
- T
o
is the time required to cross the affected bridge length (L) during the normal
flow conditions, (hour),
- L
D
is the length of the detour, (km),
- V
D
is the posted detour speed, (km/hr).
If the traffic is forced to detour and the length of the detour is not mentioned as in the
construction and demolition stages, assume the length of the detour and the detour velocity are
equal to:
Lenght The Bridge LD × = 3
0 85 , 0 V VD × =
3.4.5 Work Zone Duration (Nt)
The duration of the maintenance/rehabilitation activity is a major factor in determining the number
of days a work zone is required. The work zone duration is defined as the length of time a work
activity occupies a specific location. The manual of uniform traffic control devices (MUTCD)
(USDOT/FHWA, 1998) divides work duration into the following five categories:
o Long-term: for several days or more
o Intermediate-term: from a minimum of one day up to several days
o Short-term: for no more than 12 hours
o Short-duration: for up to one hour
o Mobile-work: a work zone that moves continuously
Work Zone Velocity (V
wz
)
"The safety of motorists and construction workers is the top priority of the department," said
Transportation Secretary Gene Conti. "Speeding is the number one contributing factor in work zone
crashes and the results of this partnership should remind motorists that it will not be tolerated."
- 28 -
o Road User Cost Manual (NJDOT)
Generally a 10 - 15 mph reduction in the normal speed (V
0
).
o Chen and Schonfeld, 2003,
On average, V
wz
is equal to 50 km/hr work zones V
0
equal to 80 km/hr
o Michigan Vehicle Code, 1974,
Work zone speed is 45 mph maximum unless otherwise posted,
o National Cooperative Research (NCHRP) report 1996, 2006 adopted by AASHTO,
Maximum speed reduction should not exceed 10 mph,
In case of worker existence on the work zone, V
wz
should be less than 45 mph,
o North Carolina Department of Transportation 2008,
Typical speed limit reductions are 10 mph below the existing posted speed limit a
maximum 15 mph speed reduction may be used,
It is strongly recommended that no speed limits below 55 mph be posted on fully
controlled access facilities,
Speed reduction should applies to an area 1/2 mile in length or greater.
o Recommended Values of V
wz
,
Generally a 15 - 25 mph reduction in the normal speed (V
0
).
Table 3:7 Average vehicle length according to bridge configuration
Normal speed V
0
(km/h) 30 40 50 60 70 80 90 100 110 120
Recommended V
wz
(km/h) 25 30 40 50 60 65 75 85 90 95
3.5 Traffic Characteristics
Bridge user costs are directly dependent on the volume and operating characteristics of the traffic
on the bridge. Each construction, maintenance, and rehabilitation activity generally involves some
temporary impact on traffic using the facility. The impact can vary from insignificant for minor
work zone restrictions on low volume facilities to highly significant for major lane closures on high
volume facilities.
The major traffic characteristics of interest for each work zone include such factors as the overall
projected Average Daily Traffic (ADT) volumes, the associated 24-hour hourly traffic distributions,
and the vehicle classification distribution within the traffic stream. Each of the major traffic
characteristics is discussed in the sections that follow.
3.5.1 Vehicle Classification
Bridges users are not a homogeneous group. They include commercial and non-commercial
vehicles ranging from motorcycles and passenger cars through the heaviest trucks. Appendix of the
- 29 -
FHWA Traffic Monitoring Guide, Third Edition (February 1995) includes 13 different vehicle
classifications. These different vehicle types have different operating characteristics and associated
operating costs.
For simplification of vehicle classifications and consistency with available traffic data, it is
recommended to use Passenger Car and Truck classifications only.
The Truck Percent from the ADT (r
T
)
Of course the percentage of the truck on bridges is differing from case to case. Many case studies
were tock place to compute the average percent of trucks on the roads or bridges. The following
information and equation are concluding some.
o Calgary Region External Truck Survey Study 2001:
Average for All Locations 15.3%
o FSOT Florida Traffic Information 2002 :
Average for All Locations range from 7,36% to 11,74%
o Based on analysis of intensive traffic surveying data, the recommended value
40 , 8 0001 , 0 + = ADT rT
Where:
- r
T
is the percentage of trucks from the AVD,
3.5.2 Traffic Growth Rate
Due to factors such as population growth and economic prosperity, the volume of traffic on bridges
increases each year. Johnston et al. (1994) estimated that the traffic growth on interstate highways
is 4.06% and on other highways is 1.94%.
Calvano (2003) stated that in Canada the traffic growth between 2006 and 2011 is estimated to be
1.1%. Based on these values, the current ADT estimate in the present user cost model is given in
the following equation,
m t
t
Year Year
ADT ADT
?
+ × = %) 1 . 1 1 (
Where:-
- ADT
t
is the ADT to be used in the analysis at year t, (Vehicle/Day),
- ADT is the measured average daily traffic, (Vehicle/Day),
- Year
t
is the current year,
- Year
m
is the last year in which the ADT is measured.
3.5.3 Traffic Control Plan (TCP)
The basic concept of a traffic control plan is to permit the contractor to work on a bridge while
maintaining a safe and uniform flow of traffic. TCP are chosen based on the number of bridge lanes
and the type of repair. Table 3:8 and Figure 3:5 illustrate some available bridge TCP.
- 30 -
Table 3:8 Suggested Traffic Control Plans for Bridge Configurations
Direction Lanes Bridge Configuration
Type
Normal Open
TCP Notes
Two-Lane Undivided 1 1 Plan 1 One lane open for traffic in two directions
Two-Lane Divided 1 1 Plan 2 Shoulder used as a lane in the work zone (*)
Four-Lane Undivided 2 1 Plan 3 One lane closed in one direction
Four-Lane Divided 2 1 Plan 3 One lane closed in one direction
Six-Lane Undivided 3 2 Plan 4 One lanes closed in one direction
Six-Lane Divided 3 2 Plan 4 One lanes closed in one direction
Six-Lane Undivided 3 1 Plan 5 Two lanes closed in one direction
Six-Lane Divided 3 1 Plan 5 Two lanes closed in one direction
Multilane >3 ?2 Plan 6 Two lanes closed in each direction
Special Traffic control Planes
Six-Lane Undivided 3 1,5 Plan 7
Two lanes closed in one direction and
one lane in the other direction
Deck full replacement 0 Plan 8 Full bridge closure and complete detour
Figure 3:5 Suggested Bridge Traffic Control Plans (TCP)
(*) in this case, the cost of the temporally shoulder must be added as extra cost
- 31 -
3.5.4 Bridge Traffic Capacity
Bridge traffic capacity is the maximum number of vehicles passing a point on the bridge at
established bridge conditions. In analyzing bridge work zone related user costs, there are two
possible capacities:
o The capacity of the bridge under normal operating conditions,
o The capacity of the bridge when the work zone is in place,
Normal Bridge Traffic Capacity
Normal Capacity is the maximum traffic volume a bridge can handle under normal bridge
conditions. Table 3.9 provides the ideal capacity a facility type can handle. The normal capacity of
the bridge is used during the non-work zone hours when all traffic lanes are open.
Table 3:9 Normal Bridge Traffic Capacity
Bridge Configuration Type Ideal Capacity Veh/lane/hour
Two-Lane Undivided 1,400
Two-Lane Divided 1,400
Four-Lane Undivided 2,100
Four-Lane Divided 2,100
Six-Lane Undivided 2,200
Six-Lane Divided 2,200
Multilane Highway bridge 2,300
Work Zone / Detour Capacity
Bridge capacity in the work zone is estimated from research studies according to intensive traffic
data, and adopted in this chapter according to the traffic control planes Table 3.10 reflects average
vehicle flow capacities at several real world work zones under several lane closure scenarios.
Table 3:10 Bridge Traffic Capacity in Case of Work Zone
Bridge Configuration Type
Traffic Control Plan
(TCP)
Recommended Average Capacity
Veh/lane/hour
Two-Lane Undivided Plan 1 600
Two-Lane Divided Plan 2 900
Four-Lane Undivided Plan 3 1,300
Four-Lane Divided Plan 3 1,300
Six-Lane Undivided Plan 4 1,400
Six-Lane Divided Plan 4 1,400
Six-Lane Undivided Plan 5 1,200
Six-Lane Divided Plan 5 1,200
Multilane Plan 6 1,400
- 32 -
3.6 Developed (BUC) Computer program & Practical Example
As culmination of the progress in this chapter, a simple Excel based computer program was
developed; to illustrate this model let us take a real example during a bridge design competition.
3.6.1 Practical Example
Overview
The project objective is to build, maintain, and eventually dispose of a new interstate bridge. The
engineer first makes a general description of the size of the bridge and the environment in which it
will exist. The structure is 115 meters long, 14.5 meters wide. The bridge is part of an interstate
highway that has a currently traffic volume of 35,000 Vehicle per day. The unrestricted design
speed is 90 km/hr. The engineer next lists the minimum performance requirements of the structure
that all design proposals must satisfy. The structure must be able to carry the loads prescribed in
Bro 2004 specification. The spans between piers must not deflect more that L/800 meters.
A four lanes conventional reinforced concrete bridge is on of the proposed design alternatives
which satisfied these performance-based requirements during design competition.
The target now is to calculate the total bridge user cost that will incurred by this design proposal
during its whole life cycle.
3.6.2 Application using the developed computer program
The developed bridge user cost model is available and can be order from KTH or from the author,
the model has four windows, the input window, assumption window, work activation and
deactivation window, and the output window. Consequently, using the above mentioned example,
the input data window is shown in Figure 3:6 below.
Input Data Window
Figure 3:6 BUC computer model window No. 1 (Input Data)
- 33 -
3.6.3 Assumptions Window
All of the assumptions are according to the above mentioned system and formulas, but the user can
change them according to the bridge situation. Accordingly, the assumption window is shown in
the following figure.
Figure 3:7 BUC computer model window No. 2 (Assumptions)
3.6.4 Working Tasks Activation Window
According to the bridge type, the user can activate or deactivate of the proposed actions and can
also change the intervals or add other working activities. Consequently, using the above mentioned
example, work activities window is shown in Figure 3:8 below.
- 34 -
Figure 3:8 BUC computer model window No. 3 (Tasks Activation)
3.6.5 Calculation Sheets
The time delay calculation sheets are hidden sheets within the model. Consequently, using the
above mentioned example, the time delay calculation sheets which present the computation system
are presented in Table 3:11 and Table 3:12 as follow.
- 35 -
Table 3:3 BUC Computer model, Time Delay Calculation Sheets
- 36 -
Table 3:4 BUC Computer model, Queued Vehicles Calculation Sheet
3.6.6 Results Window
The forth window is the output window. Obviously the bridge user cost is shown according to
Figure 3:1, which presents the costs according to the project stages and according to the user cost
type. Figure 3:9 illustrate the result of the above mentioned example.
Figure 3:9 BUC computer model window No. 4 (Output)
- 37 -
4. BRIDGE AESTHETICAL AND CULTURAL VALUE
4.1 Introduction
This chapter is a development, adaption, and modification to the appreciating work which carried
out in ETSI II project /SP 3 subproject, by project group which consisting of following persons:
o Dipl. Eng. Seppo Aitta from the Finnish Road Administration
o Civ. Eng. Hans Bohman from the Swedish Road Administration
o Civ. Arch. Eldar Høysæter from the Norwegian Road Administration
o Dr Tech. Aarne Jutila from Insinööritoimisto Extraplan Oy.
4.1.1 Background
Bridges have been part of human settlement for thousands of years. Historic bridges stand as
evidence of the power and influence of past societies. They vary greatly in style and reflect the
culture and engineering innovation of their society.
Bridges are often seen more or less as sculptures and icons to which the citizens may relate as the
soul of the city. This atmosphere and the will to identify the town and its values with an icon may
motivate for bold and spectacular solutions. Some projects have exceeded all cost estimates but still
it has been possible to fulfill them with success.
Modern bridges exploit the latest technologies and construction techniques. They allow us to
challenge the landscape in new ways and so impose our hand on the landscape. It is important to do
so well. Location of a bridge, cultural values of the surroundings, landscape, viewpoints of local
people, and our understanding of the context should guide our solutions. In short, our bridges
should be beautiful.
4.1.2 Objective
The aim of this chapter is to facilitate the evaluation of bridge aesthetical and cultural values and
relate them to the other important aspects of bridge design and construction, i.e., functionality,
economics and techniques.
The second target is to setup some basic design guidelines which can help design teams to produce
bridges of aesthetic value, or at least keep them aware of the bridge aesthetics evaluation process.
4.2 Issues to be Considered
Ranking of bridges and bridge design proposals is a difficult task. Especially difficult it is, if we
have to make aesthetical and cultural values of bridges measurable with other values like cost. At
the first sight the easiest way seems to be to establish some kind of jury to evaluate different
proposal. Of course the judgment of the jury would be based on individual opinions without an
exact scale of measuring. However, an open question still remains: how to convert the judgment to
money that seems to be the only common value available when comparing different things. It is
- 38 -
generally acknowledged, that such a jury in the case of bridge construction should consist of
experts with right education, profession and position, e.g. owners, bridge engineers and architects.
In some cases even ordinary people of the local community could be represented.
For the decision making and to bases the work of the jury, some guiding principles have to be
setup. The main issue to be clearly stated is where to put weight when comparing different
alternatives. This is even more important, if the bridge has special dignity.
In the decision making the following issues have to be considered:
Classification of bridge sites and its corresponding acceptable additional relative costs
The considered items and issues and to give them appropriate weights
4.2.1 Bridge site classification
In Finland the so-called classification of bridge sites is used. This system was developed by the
Finnish Road Administration (Finnra). It considers the value of the scenery. A publication
"Siltapaikkaluokitusohje" (Guide for Grading a Bridge Site) already exists (in Finnish).
A four-grade system is used for evaluation of a bridge site:
o Class I Very demanding considering the landscape and city view.
o Class II Demanding considering the landscape and city view.
o Class III Remarkable considering the landscape and city view.
o Class IV Ordinary considering the landscape and city view.
Class I, “very demanding”. This means that the site includes nation wide valuable views or city
views, culturally valuable landscape or the most important joints in the transport network. Also the
most remarkable waterway crossings within the country and museum bridges belong to this group.
Class II, “demanding”, possess similar characteristics as those belonging to the previous class but
their importance is local, for instance remarkable city or village objects and big bridges crossing
waterways with less modest views.
Class III, “remarkable”, consists of bridge sites including ordinary waterway crossings and bridge
sites at crossings with heavy traffic located outside city or village areas.
Class IV, “ordinary”, consists of bridge sites including roads with low amount of traffic located in
an ordinary landscape outside city or village areas as well as sites with low importance where a
road or railway crosses a waterway. These kinds of bridge sites usually do not require any special
environmental or aesthetical consideration or design.
4.2.2 Cost and aesthetics can be complementary
Bridges of aesthetic merit need not be more expensive than ugly bridges. For example the shape of
a parapet, abutment or pier might have a negligible impact on costs but a significant improvement
visually. However if a bridge is designed to be as cheap as possible then it is unlikely that it will be
of aesthetic value. This is not to say that the cheapest bridge is necessarily the ugliest bridge,
- 39 -
however it does mean that cost and aesthetics as driving forces in the design process need to be
balanced.
‘It is unwise to pay too much. But it is worse to pay too little’
4.2.3 Corresponding acceptable additional costs
The acceptance of some additional cost due to the bridge site class and the aesthetics demands may
be reasonable; consequently an excellent design or bridge may be 30 % more expensive than a poor
solution and could still be chosen.
The relative shares of bridges in the different classes suggested in the "Siltapaikkaluokitusohje"
(Guide for Grading a Bridge Site) are given in Table 4:1. Consequently, the additional costs
compared to the cheapest possible solution are given in the same table.
Table 4:1 corresponding additional relative costs in percentage in the different classes
Bridge Site Class
Item
I
II
III
IV
Number of Bridges (%)
1…2
5…15
65…75
15…25
Additional cost allowed
0…30
0…20
0…10
0
No additional cost is allocated to bridges belonging to Class IV
4.3 Bridge Aesthetics Design Guidelines
For aesthetics to be successful, it must first be considered. It should be an integral part of design
and must be considered both in the general form and all the details that support it. The parts must
be considered as to how they contribute to the whole.
Generally bridges seem aesthetically more pleasing if they are simple in form, the deck is thinner
(as a proportion of its span), the lines of the structure are continuous and the shapes of the structural
members reflect the forces acting on them.
The aesthetics of a bridge should be considered at the conception of a project and through every
stage of development. Aesthetics is not something that can be added on at the end, it is the
final product of the planning, design and procurement process, from initial route selection,
through environmental assessment, to detail design and construction.
4.3.1 Sensitivity of the bridge type to the context and simplicity
- 40 -
Perhaps the most fundamental response to context is the choice of bridge structure. In most
instances it is span length that is the most significant factor in determining the form (and cost) of a
bridge. Bridges with a horizontal form are generally preferable to bridges on a grade over flat
simple landscapes and significant expanses of water. This can be shown in the following figure.
Bridges with a horizontal form are generally preferable
Figure 4:1 Proper bridge horizontal form
The accepted approximate relationship between span and superstructure type is as
follows.
o Short span (up to approximately 18m): pre-stressed concrete plank bridges.
o Short to medium span (approximately 18-40m): pre-stressed concrete girders or pre-
stressed concrete voided slabs.
o Medium span (approximately 40-80m): steel or post-tensioned concrete box girders
or incrementally launched girders.
o Medium to long span (up to approximately 300m): balanced cantilever.
o Long span (up to approximately 800m): cable stay.
o Very long span (longer than 800m): suspension bridges.
- 41 -
4.3.2 The bridge form as a whole
Proportion
The dictionary defines proportion as the proper relationship between things or parts.
Depth to span ratio
The proportion between depth of superstructure and bridge spans is an important ratio. It is
referred to the slenderness of the bridge and is defined as the span length divided by beam
depth. Common ratios can vary from 5 to 30. The ratio of five can result in a very chunky
bridge although with appearance of strength while 30 can lead to very slender bridge. For a
common pier and girder bridge, ratios generally vary between 15 and 20. These notations
and recommendations are given in Table 4:2.
Table 4:2 Proper proportions guidelines
Depth to span ratio
Bridge with a slenderness ratio of
approximately 1:12.
Captain Cook bridge, a slenderness ratio
of approximately 1:18.
Deck to parapet depth ratio Span to parapet depth ratio
The ratio of deck overhang relative to
parapet depth is also considered a significant
aesthetic proportion and guidelines have
been developed by Cardiff University School
of Engineering.
A ratio has been developed by Frederick
Gottemoeller in his book for the relationship
between span and depth and parapet height.
These formulae form the basis for a guide to
visual proportions.
- 42 -
Symmetry, Order and rhythm
Symmetrical bridges are often more aesthetically pleasing than nonsymmetrical bridges and
symmetry should not be departed from unless for a good reason. Figure 4:2 schematically
present the affects.
Rearranging the parts provides an ordered and pleasing whole
Figure 4:2 Bridge Symetry apperancess
Unity of design and detail important
Careful consideration of interrelationship of each element, and their relationship with the whole is
necessary at all stages of the design process. Good detailing is essential to good bridge design and
lack of attention to detail can spoil an otherwise beautiful bridge.
4.3.3 The bridge Parts
Superstructure
Parapet
The outer face of the parapet can be one of the most important aesthetic elements of a beam bridge.
It is the highest piece of the bridge and often the most dominant in long distance views. The
following principles (Figure 4:3) should be considered in the design of the parapet.
Figure 4:3 Proper parapet design principle
- 43 -
Girder elevation
Table 4:3 Proper girder elevation design guidelines
Hunched girders are expressive and
responsive to the forces in the bridge. They can
often be more distinctive and elegant than single
depth beams
Long haunches smoothly tapering out are
much more graceful and responsive than short
abrupt haunches.
Three or five span haunches are aesthetically
very elegant balanced structures.
Avoid a sharp angle between haunch and
beam.
Girder cross section
Table 4:4 Proper girder cross section design guidelines
Maximizing the overhang will increase the
shadow
An angled connection will minimize this effect
A very acute angle provides a deep
shadow nearly all of the time
A curved soffit will provide a gradation of tone
and minimize a sharp line at the base of the
beam.
- 44 -
Substructure
Headstock
When they are used they draw attention to the pier and the method of support, if avoided
they better allow the superstructure to dominate the bridge view. Table 4:5 schematically
present the affects.
Table 4:5 Proper Headstock design guidelines
The headstock and pier combination on this
bridge adds unnecessary complexity and detail
If possible headstocks should not extend
across the outer face of the girder. This
introduces unnecessary complexity and
appears in elevation as if the headstock is
supporting the deck rather than the girder
Abutment
Table 4:6 Proper abutment design guidelines
Visible size
Spill through abutments allow open views to the
landscape and better visibility to the road beyond.
Reducing the abutments can create a
more refined and better looking bridge. It
does however increase the span and
therefore depth of beam.
Placement
Continuing the superstructure or the parapet allows
the shadow line to reduce the dominance of the
abutment, and makes the bridge appear longer and
more elegant.
Shape
Angling the abutments provides a more
open sleek look and helps visually anchor
the span.
- 45 -
Piers
Table 4:7 Proper Headstock design guidelines
Longitudinal pier spacing
Too many piers can appear cluttered, while too few
piers can result in an overly dominating deep beam,
a balance is required
Multiple piers
When placed too closely multiple piers can
appear complex or wall like, Collecting
multiple piers into pairs or clusters can open
up views below the deck and also give
rhythm and elegance to the supports.
Pier cross section
Pier shapes with only two lines of symmetry (e.g.
ellipses or rectangles) and transverse to the
centerline of the deck are preferable to squares and
circles as they present the thinnest edge to the side
view. Rounding off the corners of rectangular
piers provides a softer form, which may be
preferable in certain contexts
Pier short elevation
Pier shapes which have a slight taper can
add elegance by visually adding weight to
the bottom where stresses are greatest,
economically a taper of around 1:80 is
desirable the reverse taper should only be
used where the appearance of rigidity is
required between superstructure and pier.
Pier long elevation
A taper can appear elegant and better represents
the structural forces acting upon the pier
One significant advantage with a reverse taper is
that it facilitates the elimination of the headstock
- 46 -
Details
Table 4:8 Proper bridge details design guidelines
Joints and connections
A nice joint can enhance the bridge design and
provide another level of detailed aesthetic
interest.
Bridge barriers & Railings
A two rail barrier is better than a single
rail barrier in this respect
Safety screens
An outward curving screen creates a more open
feeling for bridge users and reduces the
opaqueness of the top of the mesh for road users.
However it presents a greater apparent depth of
structure for onlookers.
The screens should extend to the ends of the
bridge span.
Lighting and color
The light columns should relate to the other
bridge elements in position and form. Where
possible lighting on bridges should be
minimized or avoided.
A neutral palette of black, grays and white
colors tend to give a clear definition of the
bridge as an object in the landscape.
- 47 -
4.4 Unique Evaluation System
4.4.1 Body of the system
The system is based on the idea that points given to different things according to a given scheme
and the opinion of the evaluators. The number n of things to be considered can be freely chosen
and each thing can have different weight w
i
of importance.
The evaluator rule is to give a numerical values or points p
i
on a chosen scale to each thing i
that is considered.
For each thing i the scale can be different, but essential is, that the extreme values p
imin
and
p
imax
are related to each other so that always
For evaluating the effect of aesthetical and cultural aspects, Aesthetical coefficient k
AES
calculated
by the equation
Here a is another non-dimensional scaling factor by which the effect of these aspects can be
regulated. Finally, the relative aesthetical and cultural value cost C
RACV
of a design or a bridge, is
then obtained by equation
Here C
AG
is the Agency cost obtained by cost calculation considering the construction, repair,
maintenance and demolishing costs of the bridge from its whole lifetime. Consequently, the final
life cycle cost of the bridge LCC is
Where:
o C
AG
is the corresponding Agency cost.
o C
USER
is the corresponding User cost.
o C
RACV
is the corresponding Relative Aesthetical and Cultural Value cost.
o C
REI
is the corresponding Relative Environmental Impact cost.
The system described above enables comparison between different design proposals, existing
bridges and bridge types as well as evaluation of even different construction methods.
?
?
=
=
? =
n
i
i i
n
i
i i
AES
p w
p w
a k
1
max max
1
REI RACV USER AG C C C C LCC + + + =
AG AES RACV C k C =
max min Pi Pi ? =
- 48 -
075 ,
10
5
15 ,
) 2 3 ( 2
) 1 1 ( ) 2 2 (
15 , ? = × ? =
+ ×
× + ×
× ? = AES k
4.4.2 Numerical values for p
i
and a
The scale for points p
i
and the corresponding individual values should be chosen so that an
evaluator has enough possibilities to distinguish the different designs or bridges, but at the same
time not too many categories to keep the evaluation process simple. That is why it is proposed
that
a) The scale for each item is the same,
b) The scale varies from -2 to +2
c) Only five categories with even steps are used.
When so, the extreme values p
imax
have a constant value p
max
= 2 and the categories are as
presented in Table 4:9.
Table 4:9 Numerical values for the evaluation system and its meaning
Category Explanation
-2 Poor
-1 Modest
0 Medium
1 Good
2 Excellent
For the non-dimensional scaling factor a numerical value a = 0.30 is recommended as it used
also in (Guide for Grading a Bridge Site) are given in Table 2. That means that in the extreme
cases the Aesthetical coefficient k
AES
varies between -0.30 and +0.30. This may be reasonable,
because consequently an excellent design or bridge may be 30 % more expensive than a poor
solution and could still be chosen.
With the values mentioned above Eq. (2) takes a reduced form
To demonstrate the system above, let us take a simple artificial example. Let us assume our
bridge is belonging to class II, and we have only two things to consider: aesthetics and culture.
Let us consider weight w
1max
= 3 and the latter one weight w
2max
= 2 (weights belonging to the
maximum case, case I). Let say in bridge case II the former one have weight w
1
= 2 and the latter
one weight w
2
= 1. Let us further assume that our bridge was given 2 points for its aesthetical
values, i.e., p
1
= 2, and 1 point for cultural values, i.e., p
2
= 1. Thus the Aesthetical coefficient
k
AES
takes the value
?
?
?
?
?
?
=
=
=
=
=
=
? = ? = ? =
n
i
i
n
i
i i
n
i
i
n
i
i i
n
i
i i
n
i
i i
AES
w
p w
w
p w
p w
p w
a k
1
max
1
1
max
1
1
max max
1
15 ,
2
3 , 0
- 49 -
Which means that, because the bridge proposal that we are evaluating is beautiful or have
a good value of aesthetics and culture, so it will reduce the agency cost by = 0,075 = 7,5 %.
In case where k
AES
is (+ ve), that’s mean the proposal that we are evaluating is ugly or have bad
aesthetical and cultural value, so it will increase the agency cost by the value of k
AES
4.4.3 Bridge site classes
The same four classes which used in the publication "Siltapaikkaluokitusohje" (Guide
for Grading the Bridge Site) mentioned above. According to that publication, there are
four different bridge site classes as follows in Table 4:10
Table 4:10 Bridge site classes and its meaning
Class Explanation
Class I Very demanding
Class II Demanding
Class III Remarkable
Class IV Ordinary
That means that Class IV is the lowest one and does not require any special aesthetical attention,
where no additional cost is allocated to bridges belonging to this class (Table 3.2).
4.4.4 Recommended considered evaluation items
The numerical values w
i
recommended here are dependant on the bridge site classes. For a
computer program to be developed, the user is then supposed to evaluate these items according
to the proposed scale. Depend on particular cases, the user is supposed to change these values
to more suitable values or some times neglect or add other things, if needed. The recommended
consider items are presented in Table 4:11 as follow.
- 50 -
Table 4:11 List of the evaluation considered items and its weight factors in each bridge site class
4.5 Practical Application and Testing
4.5.1 The case background
As a practical application of how we handle aesthetics, we can look at the current (2009) bridge
over the Motala Bay in the Middle of Sweden. In order to get a nice and beautiful bridge, a
bridge design competition was arranged. Seven architectural firms were invited to participate.
Nine different proposals were sent in to the Swedish National Road Administration.
The proposals on, how to design the bridge, should contain a lot of documents describing the
bridge from a lot of different aspects as:
The Motala Bay Bridge is located in a small town called Motala. The town was founded in 1822
and has 30 000 inhabitants. It is situated in the western part of Östergötland by the Göta Canal
outlet into Sweden’s second largest lake, Lake Vättern, right between Stockholm and
Gothenburg. The bridge - still in design phase in early 2009 - crosses the Motala Bay and will be
about 600 meters long. The map of the building site is shown in Figure 4:4
- 51 -
Figure 4:4 Map of the Motala Bay Bridge area.
4.5.2 The considered design proposals
Three design proposals are considered here.
Proposal Nr. 1 is a continuous steel-concrete composite box girder bridge with inclined struts
supporting the side cantilevers and inclined V-shape legs made from steel around the main span
that is 156 meters long. The side spans are 72 and 123 meters on one side and 123, 72 and 42
meters on the other, altogether six spans. The sum of spans is 588 meters and the total length 610
meters (Figure4:5 and Figure 4:6).
On both sides of the bridge there is a pedestrian and cycling lane slightly below the road level.
The cross-section is symmetric with respect to the center line of the bridge and constant
throughout the bridge. The steel box part of the superstructure is supported by the sub-structure.
Longitudinally the bridge is symmetric with respect to the waterway, but outside that area it is
not. Due to the modest structural depth, 4 meters, the height of the bridge remains relatively
small reducing the maximum slope to 35 %
0
. Vertical clearance under the bridge is 22,5 meters
on a length of 40 meters. Embankments are not steeper than 1:2. Indirect lighting and spotlights
on the inclined legs will be provided. The traffic density on the bridge will be about 6300
vehicles per day.
- 52 -
Figure 4:5 Side view of the bridge according to Proposal Nr. 1.
Figure 4:6 Perspective view of the bridge according to Proposal Nr. 1
- 53 -
Figure 4:7 Side view of the bridge according to Proposal Nr. 2
Proposal Nr. 2 is a continuous steel-concrete composite box girder bridge with a long arch span,
191 meters, in the middle. The bridge consists of nine spans: 40+3x48+191+3x48+40 = 559
meters. The arch is made from steel. The width of the bridge is 23 meters. The height of the
bridge is 25,5 meters and vertical clearance in the main span is 22,5 meters on a length of 40
meters. The arch is curved in horizontal plane just as the girder, too. There is a pedestrian and
cycling lane on one side of the deck (Figure 4:7 and 4:8 and 4:9). The traffic density on the
bridge will be about 6300 vehicles per day. The design life length of the bridge is planned to be
120 years.
- 54 -
Figure 4.8 Perspective view of the bridge according to Proposal Nr. 2.
Figure 4.9 Perspective view of the bridge according to Proposal Nr. 2.
- 55 -
Figure 4.10 Perspective view of the approaching span according to Proposal Nr. 2.
Proposal Nr. 3 is a continuous prestressed concrete box girder bridge whose 6 out of 13 spans
are supported by cables. So the bridge actually is a combined box girder and cable-stayed bridge.
Its spans are 36+2x54+60+4x72+60+3x54+42 = 756 meters. The total width of the deck is 24,7
meters. In the cable-supported spans there are four and in the other spans 5 boxes side by side. The
deck is unsymmetrical with respect to the center line of the bridge and to the cable planes that
are located in the middle of the bridge. There is a pedestrian and bicycle lane only on one side
of the bridge. The five pylons supporting the stay-cables form a monolithic structure with the
superstructure without any joints. At the other piers, however, and at the abutments the
superstructure is supported by bearings. The design life length of the bridge is planned to be 120
years. Photomontage views of the bridge are shown in Figure 4:11, 4:12, and 4:13.
- 56 -
Figure 4:11 Side view of the bridge according to Proposal Nr. 3
Figure 4.12 Perspective view of the bridge according to Proposal Nr. 3.
- 57 -
Figure 4.13 Perspective view of the approaching span according to Proposal Nr. 3
The following figure presents the three design proposals including superstructure and the whole
bridge cross section for each alternative.
Figure 4:14 Conclusion of the given data in the three proposals
- 58 -
4.5.3 The evaluation process
The testing procedure was carried out so that each of the four evaluators studied the documents
available and then individually tried to evaluate first the bridge site and then the proposals
themselves. Finally the outcome was compared and discussed.
The bridge site classification
Evaluation of a bridge site should be based on maps and documents available and on site visits.
Four different items were evaluated and the corresponding bridge classes were determined
corresponding to each item. Consequently the final bridge site class could be determined. The
process is described in Table 4:12.
Table 4:12 The process used in the evaluation of the Motala Bay Bridge class
Evaluated item Class Arguments
Location of the bridge site II
The bridge site is located between two inhabited
islands. There is settlement on both shores and due
to that the daily traffic is considerable.
Furthermore, the road leading to the ferry is part of
the archipelago ring road that is kept open for
tourists in summer time. The bridge will replace the
present ferry.
Value of the landscape I
Björkö and Mossala villages with there storehouses
on shore are considered as a valuable landscape
even on countrywide level. The bridge site is part
of this valuable cultural landscape.
Cultural value of the
bridge site
II
Important environment considering the history of
the area. In the vicinity there is the Lills-Kills croft
that is protected by the support of the building
protection law.
Aesthetical demands of
the bridge
II
The bridge is part of valuable landscape. The
bridge may not be a too dominating element but
shall be suited to the nearby surrounding.
Overall evaluation of the
bridge site class
I-II Especially demanding or demanding bridge site.
After a short discussion, however, it was not difficult for the evaluators unanimously to agree that
the bridge site class in this case is Class II (“Demanding”). That fixed the weights accordingly
(Table 4:11).
Evaluation of the bridge proposals themselves
The most difficult part is to define the considered items and the weight factors for the
different items in each of the three cases, followed. Consequently, value 0,30 for the scaling
factor a was accepted. The item list was agreed to be the one proposed in this report Table4:11.
- 59 -
Consequently, according to Table 4.11Class II
Thus, Consequently:
The complete results of the evaluation are presented in a compact mathematical form below. The
Aesthetics coefficient kAES is of main concern. In this particular case (bridge site class II)
According to Table 3.12 Class II, to cover all evaluation cases, a matrix presentation is used. Thus,
weight vector {wi} is:
Where {kAES} is the final Aesthetics coefficient vector dimension 1x5, (pi) is the evaluation result
matrix, dimensions 5x20, which in this case has the value
?
?
?
?
=
=
=
=
? = ? = ? =
20
1
20
1
1
max max
1
II) (
II) (
0015 .
200
30 . 0
i
i i
i
i i
n
i
i i
n
i
i i
AES p w
p w
p w
p w
a k class
class
? ?
= =
= + + + + + = =
n
i i
iclass i w w
1
20
1
100 6 .. .......... 4 6 6 12 1 max
[ ] [ ] 4 3 3 2 3 2 3 2 3 3 5 4 4 4 2 2 3 4 4 8 II) ( = class i w
200 100 2 2 1
20
1 1
max max = × = =
? ?
= = i
n
i
i i iclass w p w
- 60 -
In the case of Proposal Nr. 1 the evaluation result matrix {pi} takes the form
In the matrix, the first column represents the points which the first evaluator gave to the twenty
different items. The points are listed in the same order as in Table 4:11, or in the list just above Eq.
Similarly, the second column consists of the points given by the second evaluator, and so on until
the fourth column, which is related to the fourth evaluator. The values in the fifth column are
simply the roundup average values of the four previous ones on the same row.
When the operation shown by equations is carried out using the numerical values presented in
above, the final results will be as follow.
{ } { } 114 . 134 . 102 . 104 . 108 . ? ? ? ? ? = ASE k
The same for Proposal Nr. 2, the final aesthetics coefficient vector {kAES} takes the form:
{ } { } 128 . 142 . 122 . 121 . 118 . ? ? ? ? ? = ASE k
Similarly for Proposal Nr. 3 final Aesthetics coefficient vector {kAES} takes the form:
{ } { } 074 . 091 . 041 . 064 . 084 . ? ? ? ? ? = ASE k
The test carried out shows that the evaluation method developed is easy to use and
[ ]
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
¸
(
¸
? ? ? ?
=
1 0 1 2 1
2 2 2 1 1
1 1 1 2 1
1 2 1 0 2
2 1 2 2 2
1 1 2 1 1
1 1 2 1 0
1 2 1 1 0
2 2 1 2 2
1 1 1 0 1
1 0 1 2 1
1 1 1 2 1
1 1 1 1 2
1 2 2 1 0
1 1 1 0 1
1 1 0 2 2
2 1 2 1 2
2 2 1 1 2
1 2 1 1 1
1 2 0 1 1
i p
- 61 -
mathematically simple. The judgments of the four evaluators were in most cases surprisingly
similar. Although some differences appeared in some details, they were greatly balanced out in
the final result. The smallest differences are in the cases of Proposal Nr. 1 and Proposal Nr. 2,
where the Aesthetics coefficient k
AES
varies between -0,102 and -0,134, and -0,118 and -0,142,
respectively. In the case of Proposal Nr. 3 the variation is bigger, from -0,041 to -0,091, but
even in this case every evaluator comes to the conclusion that the aesthetical and cultural values
of the proposal are positive. Based on these results Proposal Nr. 2 seems to be slightly
superior to Proposal Nr. 2 and Proposal Nr. 3. And it occupies the last position in this
evaluation.
Better than to compare the judgments of individual evaluators might be to compare the average
values. According to Eqs., the variation between the different proposals is extremely small, from
-0,114 to -0,128 in the average values. Maybe the average value give more objective result, when
there are several evaluators, as it was the case in the test evaluation carried out. The final order
between the three proposals, however, is still the same: Proposal Nr. 2 is slightly superior to
Proposal Nr. 2 and Proposal Nr. 3 occupies the last position
4.6 Developed Computer Program
As a culmination of progress in this chapter and its unique aesthetics evaluation system, a simple
computer program is developed. The program is composing all of the things which is explained
and mentioned in above in a very simple systematic way. The program can as easily be used by
an individual as by a jury or group of evaluators. The front page shape is as shown in Figure 4:15.
- 62 -
Figure 4:15 shape of the developed computer program
4.6.1 Introduction
Practical use of the program is simple, only 4 steps to get the bridge proposal equivalent
aesthetical and cultural coefficient K
AES
o, the user is only have to chose the alternative form a
build up list of choices, he don’t have to enter any other values, or perhaps he may have to, if he
decided to change the weight factors of the considered items to suit down his case of study.
- 63 -
4.6.2 Working steps description
The first Step is to agree about the value the scaling factor a. It also needs to be determined in
advance, because it has a decisive influence on the level of appreciation of aesthetical values
compared to costs. The value 0,30 is recommended and its sounds reasonable, because in extreme
cases it restricts the effect of aesthetics up to ±30 %, but of course also any other value between
is possible. Even this value should be determined by the bridge owner. In Finland the are usually
using a=0,30 as its mentioned in Table 3.12
The second step is to evaluate the bridge site by determining which class the bridge site is
belongs to. However, four items have to be evaluated to reach this target and so the average
value of these four items will be the class of the bridge site.
The third step is to agree about the items that will be evaluated and to determine weight of each
item. This should be done before the evaluation process begins. The weights should be
considered as “fixed values” and may not be changed during the evaluation process. One is
totally free to choose any items and their number is by no means restricted.
Too detailed item may cause difficulties to the evaluator. In this program, almost a standard list
of items and there weights is included, which fairly cover the general bridge aesthetics demands,
it can easily be altered to meet the requirements of the project in question, whether by giving
“zero weight” to those items that are left outside consideration or/and by adding new item by
changing the last cell name form others to the new name, and give it the suitable weight factor in
each bridge site class.
The forth and final step includes the evaluation itself, i.e., the determining of points p
i
for each
considered item, however, a fixed scale is determined with p
max
= - p
min
= 2, with steps equal to 1
here one has to decide between five different values, i.e. -2, -1, 0, 1 and 2, according to his point
of view. It can be done by choosing the value form a buildup list beside each considered item.
In case of individual user, he can chose the points p
i
easily form each list according to his view
point, simply if there is a jury or group of evaluators they can use this program by entering the
average evaluation value for each consider item.
When the evaluator has decided on points p
i
, it is a simple mathematical task to calculate the
final values of Aesthetics coefficient k
AES
and all of these equations are built up in this program.
4.6.3 Example
Let us take a simple example, which may illustrate the procedure better, Let us consider the case
of average evaluation in the previous example for proposal number 1, by keeping the same value
of a=0,30 and the bridge site is belong to Class II. The average evaluation from the matrix, which
is column number 5, which is as following:
- 64 -
{ } { } 1 2 1 1 2 1 1 1 2 1 1 1 1 1 1 1 2 2 1 1 ? = Pi
Figure 4:16 Practical example in the developed program
- 65 -
Figure 4:16 describes the usage and the application of the model. By entering this values of points
p
i
in the program, consequently the value of Aesthetics coefficient k
AES
= -0.114 which is the same
value that on equation number (11) column number 5.
According to the proposed list of items and its weight factors and the recommended value of
a=0.30, the extreme values of the Aesthetics coefficient k
AES
will be as followed in table 4:13.
Table 4:13 The extreme values of the Aesthetics coefficient k
AES
according to table 3.12 data
a=0.30 Class I Class II Class III Class IV
Excellent Design K
AES
max -0.30 -0.204 -0.096 0
Bad Design K
AES
min 0.30 0.204 0.096 0
4.6.4 Practical use of the program
The program is concluding a unique system that enables to incorporate aesthetical values to
bridge design or construction projects and to make them comparable with construction and
lifecycle costs. The method can be used beneficially in the following cases:
o Evaluation of aesthetical values with respect to the initial construction costs.
o Comparison of different bridge design proposals within a project or in
engineering skills - including bridge design - competitions.
o Comparison of different routes where bridges are involved during the feasibility
study stage or construction phase.
o Rewarding - or punishing - of those involved when an aesthetically better - or
worse - result is achieved than expected.
The method can as easily be used by an individual as by a jury or group of evaluators. Due to its
simple mathematical formulation it can also be easily incorporated in a LCC computer program
to become part of it.
- 66 -
5. BRIDGE ENVIRONMENTAL IMPACT
5.1 Introduction
Environmental indicators demonstrate significant impacts of current concrete infrastructure
systems. Construction, maintenance and demolition of bridges demand materials and energy inputs,
which in turn lead to environmental impacts. New infrastructure and maintenance of existing
infrastructure has led to a global output of construction-related concrete that exceeds 12 billion tons
per year (van Oss and Padovani 2002b). This enormous volume represents huge flows of material
between natural and human systems, which is expected to increase significantly as world
population urbanizes (UNFPA 2001). Cement production accounts for 5% of all global
anthropogenic carbon dioxide (CO2) emissions (Hendricks et al. 1998, Worrell 2001) and
significant levels of SO2, NOx, particulate matter and other airborne pollutants (WBCSD 2002, US
EPA 1999, US EPA 2000).
5.2 Issued to be Considered
5.2.1 Project development stages and considerations
Modeling the complete life cycle of a bridge system is complex and data intensive. When we talk
about the bridge environmental impact we have to put in mind to consider all bridge life cycle
stages, as shown in Figure 5:1, considering the input and the output as well. The main parameters
that should be considered during the assessing process are as follow.
Figure 5:1 Bridge LCA path
Material resource consumption (The Usage of un renewable materials)
Air and water pollutant emissions
Solid waste generation
Energy use
Fuel consumption
Emissions from the traffic
- 67 -
5.2.2 Toxics Classification
There are thousands of chemicals affecting human health and the environment, hundreds of
different known mechanisms and many other unknown or incompletely known mechanisms. While
toxicologists would not normally combine compounds unless common models of action have been
demonstrated, LCA add all toxics into one overall score even if modes of actions are known to be
different.
Each of all the various environmental stressors throughout the life cycle, relative to the functional
unit, are summarized and then classified into impact categories, according to which environmental
impact(s) the stressors contribute to. Established impact assessment methods cover various impact
categories, like for instance global warming, acidification, toxicity etc. This method includes
characterization factors for 10 impact categories as shown in Figure 5:2; Abiotic depletion potential
(ADP), acidification potential (AP), eutrophication potential (EP) global warming potential (GWP),
ozone layer depletion potential (ODP), human toxicity potential (HTP), fresh water ecotoxicity
potential (FAETP), marine aquatic ecotoxicity potential (MAETP), terrestrial ecotoxicity potential
(TETP) and photochemical ozone creation potential (POCP). However, the 4 toxicity categories
are, for the time being, omitted in BridgeLCA, due to high uncertainties in the calculation principles
of these.
Figure 5:2 Bridge emissions categories
5.2.3 Toxics categories weighting impacts
The best way is to calculate the environmental impact per category using characterization
indicators. These indicators are based on the physicochemical mechanisms of how different
substances contribute to the different impact categories. E.g. Global-warming potential is one of the
environmental categories and CO2 is the equivalent for this category. Methane that is a green house
gas which contributes 23 times as much to global warming than CO2, is multiplied with a factor of
23, and added to the category as CO2-equivalents.
Environmental Impact LCA
ADP
GWP
ODP
HTP
FAETP
MATEP
TETP
PCOP
AP
EP
Used materials during
the whole bridge life cycle
- 68 -
The following graphs (Figure 5:3) present normalized and weighted results. Normalization is done
by dividing the impacts per category by the average emissions (relevant for the respective category)
per person per year, in Western Europe in 1995. Further, the normalized results are multiplied by
weighting factors, which is a measure of the categories’ relative importance. The weighting factors
used here are taken from the BEES software, and are determined by the Environmental Protection
Agency (USA).
Figure 5:3 Environmental Protection Agency (USA) emissions weighting factors
5.2.4 Life cycle assessment (LCA)
Life cycle assessment is an analytical technique for evaluating the full environmental burdens and
impacts associated with a product system (ISO 1997). Life cycle assessment is a global tool,
calculating burdens throughout the life cycle of a product, material or service. Its strength is that it
quantifies all possible environmental burdens; its weakness is low spatial and temporal resolution.
5.3 Presentation of Previous Studies
There are only few scientific publications available on the topic of environmental effects of
bridges; the relevant articles are briefly presented in this section.
Comparison of different bridge deck component alternatives
Keoleian and Kendall, compare two types of deck systems; a steel-reinforced concrete deck with
conventional steel expansion joints and a steel-reinforced concrete deck with a link slab design
using a concrete alternative (Figure 5:4); engineered cementations composites (ECC). ECC is fiber
reinforced and has a strain capacity 500-600 times higher than normal concrete. It also prevents
nearly all corrosion of girders by reducing leakage of corrosive elements usually occurring through
worn expansion joints. Corrosion of steel girders is one of the main causes for replacement of deck
and superstructure. The study includes material production, construction, use and end-of-life
management related to bridge the decks. Initial bridge construction is similar for both studies and
- 69 -
therefore omitted. Three reconstruction options are considered; bridge deck replacement, deck
resurfacing and repair and maintenance (mainly fixing of cracks and potholes). Traffic disruption
during these activities is also included. Various air and water pollutants are considered5. The ECC
link slab deck is assumed a lifetime twice the lifetime of the deck with conventional joints.
Conclusions made in the analysis are that the ECC deck yields significantly lower environmental
impacts, for all pollutants, mainly because of less need for maintenance. For both deck systems, the
construction and repair related traffic turn out to be significant for the environmental performance.
It is also concluded that prediction of maintenance and repair schedules for each system is critical
in evaluating the performance of alternative materials.
Figure 5:4 Keoleian and Kendall comparison case study
Comparison of bridge types and designs
Collings presents two studies where three bridge types and three bridge designs are compared,
respectively. The bridge types compared are a concrete cantilever bridge, a concrete cable stay
bridge and a steel arch bridge. Relative costs and CO2 emissions for the material consumptions and
the use phase of the bridges are considered. The main conclusions are that both costs and emissions
are highest for the steel arch bridge, actually twice as high as for the concrete cantilever bridge that
gives the lowest costs and emissions. Paint, waterproofing and plastics have relatively high values
per ton of embodied energy and CO2 emissions.
The bridge designs compared are a profiled girder bridge, a tied arch bridge and a cable-stayed
bridge, designed for a longest span of 120 m, and 3 smaller spans (66 m in total) at each end. Three
material choices for each design alternative are assessed. The embodied energy and CO2 emissions
from the construction phase and the CO2 emissions during the lifetime of the bridge are given,
assuming a lifetime of 120 years. Maintenance activities included are repainting, bearing
replacement, re-surfacing and re-waterproofing. Traffic disruption due to maintenance is also
included. The main conclusions from this study are that concrete bridges have lower embodied
energy and CO2 emissions. More architectural designs like leaning or distortion of elements have
larger environmental impact, as they require more materials and more complex construction.
Emissions during the use phase are approximately the same for the three material alternatives. The
maintenance activity causing most of the emissions in the use phase is resurfacing of the bridge.
The traffic disruption due to repair and maintenance are a highly uncertain parameter, as it depends
on amount of traffic, proportion of lorries and diversion distance.
- 70 -
5.4 Case study
BridgeLCA is computer program developed in the ETSI Stage 2 by Johanne Hammervold, based
on the use of three case bridges; one steel bridge, one concrete bridge and one wooden bridge. The
bridges are already built bridges in Norway, and are thus not planned for the same location. They
differ in size and are not directly comparable. The concrete bridge, Hillersvika, has longer
construction length and width, and thus requires the most materials. The steel bridge, Klenevågen,
is the shortest bridge. An overview of the bridges and key parameters are given in following Table:
Table 5:1 BridgeLCA case study parameters
5.4.1 Total weighted results
Total weighted results, given in Figure 5:5, show that Klenevågen (steel box girder bridge) causes
the highest impacts, closely followed by Hillersvika (concrete girder bridge). Fretheim (wooden
arch bridge) causes roughly half the impacts as Klenevågen. The most important categories in total
weighted results are Global Warming Potential (GWP) and Abiotic Depletion Potential (ADP) for
all three bridges. Acidification Potential (AP) is also a relatively important category, while Ozone
Depletion Potential (ODP) is negligible in these results.
Figure 5:5 Case study total weighted result
- 71 -
5.4.2 Result per bridge and category
The impacts caused by material and energy consumptions related to various bridge as totals per
bridge and impact category as given in Table 5:2 below. In the category Abiotic Depletion Potential
bridge equipment and the use phase (OR&M) also contribute substantial shares of the impacts. This
is mainly caused by the surfacing of the bridges. The original surfacing is part of the bridge
equipment, and re-asphalting is performed each 10
th
year throughout the lifetime. Asphalt, asphalt
membrane and mastic are all bitumen products, which consume raw oil in production which again
causes the impacts to the ADP category.
For all three bridges, the construction phase causes a small share of the impacts to all categories.
The construction phase includes use of formwork and building machines and transport of workers
and materials. The results show that these factors are of less importance in this analysis.
Table 5:2 Total results per bridge and category
5.4.3 Impact per m
2
surface area of the bridge
Table 5:3 show the impact for each category per m
2
of the bridge surface area. It is important to
keep in mind that a comparison per m2 will neither give directly comparable results. The material
and energy consumptions, and also transport services and operation, repair and maintenance
activities will not vary linearly relative to bridge size. One example is the abutments; the size of
these will not change if bridge length is changed, but it will change if the width of the bridge is
changed. The main load-bearing systems and their consumption of materials will differ with bridge
length and width, but only to a certain degree, and definitely not linearly.
Table 5:3 Impacts for each category, per m2 surface area of bridge
Finally, the Relative Environmental Impact cost C
REI
of a bridge, is then obtained by equation:
o k
EI
Is the environmental impact coefficient. Range from 0,0 To +0,20
Could complement information to be used in the topic, but is not presented here. For more
information see ETSI Stage 2.
AG REI C k C EI =
- 72 -
6. SUMMARY
6.1 Conclusion and Discussion
This master thesis was devoted as a research study within ETSI project, which is a Scandinavian
contributed project. ETSI project is contributed between three Nordic countries, Sweden, Norway,
and Finland. The main task of the ETSI project is to develop a Nordic unified methodology and
computer program for bridge LCC calculations.
The idea behind this study is that, bridges investment decisions should consider all of the costs and
considerations incurred during the period over which the alternatives are being compared. Bridges
are required to provide service for many years. The ability of a bridge to provide service over time
is predicated on its being maintained appropriately by the agency. Thus the investment decision
should consider not only the initial activity that creates a public good, but also all future activities
that will be required to keep that investment available to the public. It is important to note that the
lowest agency cost option may not necessarily be implemented when other considerations such as
aesthetical and cultural value, user cost, and environmental concerns are taken into account.
This research study demonstrates a unique methodology and present a new systematic way for
analysis, evaluation, and optimization of the bridge life cycle indicators like agency cost, user cost,
aesthetical and cultural value, and the environmental impact. Present a unique flexible system
integrating all of bridge life cycle issues and make them measurable and comparable like the bridge
initial cost.
Based on this unique evaluation system, two computer programs were developed to facilitate the
usage, one for calculating the bridge user cost and one to evaluate the bridge aesthetical and
cultural value. The application of this integrated model to bridge design highlighted a critical
importance of using the life cycle modeling in order to enhance the sustainability of bridges
infrastructure systems.
6.2 Recommendation and Further Research
The application of this integrated model to bridge design highlighted the critical importance of
using the life cycle modeling in order to enhance the sustainability the bridges. Fields for future
research and development can be in the following issues.
o Sorting and gathering of agency historical data to feed the LCCA process
o Degradation models for all kinds of bridges and their structural elements.
o Tools for transforming degradation models into timings for MR&R actions.
o Methodologies for describing bridges both regarding their measures, structural parts
and their conditions.
o Development of the proposed two computer models
- 73 -
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Helsinki University of Technology, Publications in Bridge Engineering. Espoo 2007, TKK-SRT-37:
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Håkan Sundquist and Raid Karoumi. TRITA-BKN. Report 128 ISSN 1103- 4289 ISRN KTH - 128 -
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