PREFABRICATED BRIDGE ELEMENTS & SYSTEMS (PBES), DECISION-MAKING FRAMEWORK

Claude NapierSr. Structural EngineerResource Center - Structures TST

Learning Outcomes

• Understand the ABC viable concepts• Understanding of barriers/obstacles to install

PBES in hours or days • Understanding of needs/opportunities to

install PBES in hours or days• Knowledge of PBES decision-making

framework

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Learning Outcomes• Be able to use flowchart and/or matrix

questions for decision making to identify important considerations to determine best course of action for bridge construction

• List and define rapid onsite construction factors

• List and define other factors impacting the decision to use ABC or prefabricated structures

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Learning Outcomes

• List and define the different costs factors influencing the PBES decision

• Be a champion to promote PBES Technology

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ABC Viable Concepts• Ground up• Material Choices• Equipment• Prefabrication• Access-logistics• Pre-assembly• Pre-purchase & fabricate• Off site Assembly• Off site roll-in or lift-in

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ABC Viable Concepts

• Incremental launching• Longitudinal versus transverse components• Contracting techniques to be considered:

– performance related specifications– warranties– design/build– cost + time– lane rental– incentive/disincentives– value engineering

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ABC Viable Concepts• Alternatives for construction

– Construction during non-peak hours• Nighttime closures• Week-end closures

– Total or partial closures– Lane closures or detours

• Public relations: keep traveling public, businesses, politicians, etc informed

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Why ABC-PBES?

ABC-PBES offers significant advantages over Cast-in-place construction. ABC-PBES results into:

• Reduced onsite construction time• Minimized traffic disruption – from months to days• Reduced Environmental impact • Improved work zone safety – improved worker

safety• Lower First and Life-Cycle Costs• Improved product quality – controlled environment,

cure times, easier access, etc.

Question: Barriers to routinely install PBES in hours or days?

Prefabricated Bridges to Accelerate ConstructionSurvey to Sample State Bridge Engineers

Question: What would help most to use PBES?Prefabricated Bridges to Accelerate Construction

Survey to Sample State Bridge Engineers

Questions: Barriers to routinely install PBES in hours or days? What would help most to use PBES?

Prefabricated Bridges to Accelerate ConstructionSurvey to Sample State Bridge Engineers

Framework for PBESDecision-Making Users

• Decision makers for bridge type• Implementers

– Designers– Project Managers

Framework for PBESDecision-Making – Format

• Introduction• Flowchart

– Decision-Making at a Glance• Matrix

– Decision-Making Questions• Decision-Making Considerations

– Questions with Discussion and References

Framework for PBESDecision-Making – In General

• PBES are better– Due to improved quality control off-site and off-the-

critical-path fabrication• PBES are faster• PBES are safer• PBES have lower initial costs

– Due to significantly reduced traffic control, risks, environmental impacts, user delay costs

Framework for PBES Decision-Making Specific Project Considerations

• Better• Faster• Safer• Is prefabrication the best solution for this

specific project ?– Lower initial costs ?– Long lasting ?

AT

A

GLANCE

Decision Making

Flowchart

RAPID ONSITE CONSTRUCTION FACTORSTraffic Volume / Emergency / Commerce / User Delay ???

OTHER FACTORSWorker Safety / Wetlands-Air Quality-Noise /

Endangered Species / Multiple Similar Sections ???

PBES CONSTRUCTION COSTS LESS ???

AT

A

GLANCE

Decision Making

Decision-Making Matrix Example Questions

Question Yes Maybe No

High traffic volume?

Emergency replacement?. . .

Worker safety concerns?. . .

High daily traffic control costs?. . .

Decision-Making Matrix• One or two factors may warrant use of PBES• Alternatively, user may assign weights to

factors• In any case, a majority of “Yes” responses

indicates PBES offers advantages

Considerations in Selecting PBES – Categories

• Rapid Onsite Construction Factors• Other Factors• Costs Factors

Considerations Category:Rapid Onsite Construction

• High ADT/ADTT?• Emergency bridge replacement?• Evacuation route, or over a railroad or navigation

channel?• Requires lane closures, detours or temporary

bridge?• If closed, or detour distances long?• Impacts critical path of total project?

Considerations Category:Rapid Onsite Construction, cont’d.

• Close during off-peak traffic periods?• Requires rapid recovery from natural or

manmade hazards, or rapid completion of future repair/rehab?

• Construction time restrictions due to adverse economic impact?

• Weather limits CIP construction?• Are spans under 200 ft.?

Considerations in Selecting PBES – Categories

• Rapid Onsite Construction• Other Factors

– Safety Concerns– Environmental Issues– Standardization– Site Issues

Considerations Category:Other Factors

• Safety Concerns– Worker safety concerns? (e.g. adjacent power

lines, high heights, or over water)• Environmental Issues

– Environmentally sensitive area? (e.g. wetlands, air quality, and noise)

– Natural or endangered species?– Historic bridge?

Considerations Category:Other Factors, cont’d.

• Standardization– Multiple similar spans?– Bridges grouped for economy of scale– Available state or national prefabricated bridge

standards?– Regional off-the-shelf components using

stockpiled standards?– Incorporation of aesthetic or context-sensitive

design requirements?

Considerations Category:Other Factors, cont’d.

• Site Issues– Problems with delivery of ready-mix concrete?– Knowledgeable available contractors?– Available prefabricators?– Contractor options for prefabrication?– Delivery to the site?

Considerations Category:Other Factors, cont’d.

• Site Issues, cont’d.– Accessibility at the site?– Prefab foundations & substructures?– Formwork & falsework requirements?– Straight/skewed/curved alignment?– Requires seismic connections?– Available connection details?

Considerations in Selecting PBES – Categories, cont’d.

• Costs– Maintenance of Traffic– Contractor’s Operations– Owner Agency’s Operations– Service Life

• Available Online Resources

Considerations Category: Costs• Maintenance of Traffic

– Changing traffic control plan?– Delay-related user costs a concern?

• Contractor’s Operations– Innovative contracting strategies?– Use of innovative equipment?– Contractor costs for insurance/bonding?

Considerations Category:Costs, cont’d.

• Owner Agency’s Operations– Necessary staffing?– Bridges grouped for economy of scale?– Broader use?– Adequate prefabrication time in contract?

• Service Life

FHWA Decision-Making Framework

Utah DOT Decision Chart

Framework Available Online

General Information• http://www.fhwa.dot.gov/bridge/prefab/ Publications• Framework For PBES Decision-Making

Why Use PBES Technologies?

• Prefabricated Bridge Advantages:• Faster (offsite & off critical path)• Safer (for traveling public & construction &

inspection personnel)• Better Quality (controlled environment)• Lower Cost (Costs comparable to or lower

than conventional construction)

Polling Question #1• Select the items that are ABC Viable Concepts.

a. Prefabrication of standard elementsb. Cast-in-place is planned on bridge alignmentc. Pre-assemblyd. Off site assemblye. Weekend or night time closures are planned.

Polling Question #2• Select the obstacles to installing PBES in hours

or days.a. Lack of education and trainingb. Lack of standards & specificationsc. Construction industry is geared up for

prefabd. Potential higher cost & limited resourcese. Durability is not a concern

Polling Question #3• Select the major components of the PBES

decision making framework.a. Decision-making flowchartb. Life cycle cost analysis toolc. Decision-making matrix of questionsd. Decision-making consideration questions

and discussionse. All of the above

Polling Question #4• Select the items that are onsite construction

factors.a. Low traffic volumesb. Emergency repair project on high ADT routec. Project has negative impact on major industryd. Highway work is on the critical path of project

and bridge is not.e. There are significant user delays if lane is closed

for construction.

Polling Question #5• If rapid onsite construction is not required for

a project, select the other factors that may make prefabrication the preferred solution.a. Bridge is high over the water and near high

voltage lines.b. Endangered speciesc. Wetlandsd. Repetitive superstructure spans and

substructure typese. All of the above

Summary and final concluding remarks Use PBES Decision-Making Framework to help accelerate

bridge construction and help change America’s driving experience and meet the customers’ needs.

Claude Napier, Senior Structural Engineer

804-775-3327, claude.napier@dot.gov

• Louis Triandafilou, Senior Structural Engineer

• 410-962-3648, lou.triandafilou@dot.gov

Resource Center, Structures TST