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Prefabricated Bridges

PBES Decision-Making Framework

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Slide 1. Prefabricated Bridge Elements & Systems (PBES), Decision-Making Framework

Claude Napier
Sr. Structural Engineer
Resource Center – Structures TST

 

Slide 2. 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
 

Slide 3. 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
 

Slide 4. Learning Outcomes

  • List and define the different costs factors influencing the PBES decision
  • Be a champion to promote PBES Technology
 

Slide 5. 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
 

Slide 6. 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
 

Slide 7. 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
 

Slide 8. 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.
 

Slide 9. Prefabricated Bridges to Accelerate Construction
Survey to Sample State Bridge Engineers

Summary: Barriers
  • Lack of education/training/experience (13)
  • Lack of standards & specifications (13)
  • Concerns about durability or details (12)
  • Higher cost & limited resources (9)
  • Lack of perceived need for speed (8)
  • Construction industry not geared up for prefab (7)

Speaker Notes:

The foremost barrier perceived identified was the lack of education, training and experience, followed by lack of standard details and specifications, then lack of connection details and their durability. It is generally perceived that prefabrication will tend to higher costs in compare to usual cast-in-place construction methods. And finally, construction industry not equipped to handle large loads to transport and erect prefabricated bridge elements.

 

Slide 10. Prefabricated Bridges to Accelerate Construction
Survey to Sample State Bridge Engineers

Summary: Needs
  • Education/training/more projects (7)
  • Design & construction standards & specifications (6)
  • Additional research/development to address concerns about durability or details (5)
  • Competitive cost & additional funding (6)
  • Appropriate projects that require speed (4)
  • Fabrication & construction equipment & methods

Speaker Notes:

Needs related to those barriers were competitive costs and additional funding, appropriate projects that require speed, and fabrication and construction equipment and methods for use in prefabricated construction.

These responses provided the basis for the development of the decision-making framework for the effective use of prefabricated bridges.

 

Slide 11. 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?

Summary: Barriers

  • Lack of education/training/experience (13)
  • Lack of standards & specifications (13)
  • Concerns about durability or details (12)
  • Higher cost & limited resources (9)
  • Lack of perceived need for speed (8)
  • construction industry not geared up for prefab (7)

Summary: Needs

  • Education/training/more projects (7)
  • Design & construction standards & specifications (6)
  • Additional research/development to address concerns about durability or details (5)
  • Competitive cost & additional funding (6)
  • Appropriate projects that require speed (4)
  • Fabrication & constructions equipment methods (5)

Speaker Notes:

The framework addresses the need for education and training on prefabricated bridges. It also includes discussions related to the other identified barriers and needs.

 

Slide 12. Framework for PBES Decision-Making Users

  • Decision makers for bridge type
  • Implementers
    • Designers
    • Project Managers

Speaker Notes:

The framework was developed for use by the representatives of the owner agency and the contractor. The anticipated users include the decision makers for the bridge type as well as those developing and implementing the details, including designers and project managers.

 

Slide 13. Framework for PBES Decision-Making – Format

  • Introduction
  • Flowchart
    • Decision-Making at a Glance
  • Matrix
    • Decision-Making Questions
  • Decision-Making Considerations
    • Questions with Discussion and Reference

Speaker Notes:

The framework consists of an introduction, a one-page flowchart, a one-page "Yes-Maybe-No" matrix, and a more in-depth section that is in a question-and-discussion format with references.

 

Slide 14. Framework for PBES Decision-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

Speaker Notes:

In general, we know that prefabricated bridge systems have good quality because of the offsite or near-site fabrication that is off the critical path and in a more controlled environment. We know that it is faster than onsite because more of the work is done prior to final installation. Because it is faster onsite, we know that it is safer for both the traveling public and the construction crews. We also know that prefabricated bridge systems can have lower initial costs due to the significantly reduced traffic control, risks, environmental impacts, and user delay costs due to the reduced number of days of onsite exposure.

 

Slide 15. 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 ?

Speaker Notes:

So we know that prefabricated bridges are in general better, faster, and safer. But, is a prefabricated bridge the best solution for the specific project under consideration? The framework was developed to help you answer that question.

 

Slide 16. Flowchart – Decision Making

The one-page flowchart allows decision-making at a glance, for example, for a high-level decision-maker who wants a high-level tool for a quick decision without getting into the technical details of a project.

Speaker Notes:

The one-page flowchart allows decision-making at a glance, for example, for a high-level decision-maker who wants a high-level tool for a quick decision without getting into the technical details of a project.

Note the color-coded categories. The blue diamonds are related to rapid construction issues (factors). The tan diamond is related to other issues that may drive a project. The green rectangle and diamond are related to cost issues. These three categories are consistent throughout the framework.

 

Slide 17. RAPID ONSITE CONSTRUCTION FACTORS Traffic Volume / Emergency / Commerce / User Delay ???

Data Flow Diagram of Rapid Onsite Construction Factors, Traffic Volume/Emergency/Commerce/User Delay ??


Speaker Notes:

Let’s take a look at the rapid onsite construction issues. As you can see, these relate to such factors as whether the bridge will experience high traffic volumes, or is an emergency project, or would cause a significant negative impact to commerce, or is on the critical path of the construction project. Such considerations drive the need for rapid onsite construction, which makes prefabrication the preferred solution.

 

Slide 18. OTHER FACTORS Worker Safety / Wetlands-Air Quality-Noise / Endangered Species / Multiple Similar Sections ???

Data Flow Diagram Entity – Do Other Factors (Safety, Environment, Repetition, etc.) Justify Prefabrication

Speaker Notes:

If rapid onsite construction isn’t required, do other factors such as worker safety, environmental issues, or the efficiency of similar sections make prefabrication the preferred solution?

 

Slide 19. PBES CONSTRUCTION COSTS LESS ???

Data Flow Diagram of PBES Construction Costs


Speaker Notes:

If rapid construction isn’t needed, and other factors don’t make prefabrication the preferred solution, what about initial construction costs? Is prefabrication anticipated to be less expensive because of the high daily expenses for traffic control through the work zone? Or are user delay costs a concern? Is liability or risk to the agency or contractor reduced with prefabrication due to the significantly reduced number of days of exposure? If so, then prefabrication is most likely the best choice.

 

Slide 20. Decision Making

Flowchart to quickly decide whether prefabrication is the best solution for the specific project under consideration. You just follow the arrows depending on whether your answer is "Yes" or "No," and you will end at either "Use Conventional Construction" or "Use Prefabrication."


Speaker Notes:

So that’s how to use the flowchart to quickly decide whether prefabrication is the best solution for the specific project under consideration. You just follow the arrows depending on whether your answer is "Yes" or "No," and you will end at either "Use Conventional Construction" or "Use Prefabrication."

 

Slide 21. Decision-Making Matrix Example Questions

Question Yes Maybe No
High traffic volume?      
Emergency replacement?      
Worker safety concerns?      
High daily traffic control costs?      

Speaker Notes:

The one-page "Yes-Maybe-No" matrix may be used in conjunction with the flowchart or as an alternative to the flowchart. It includes the same color-coded categories as the flowchart, with additional factors in each of the categories. You simply go down the questions and respond with a "Yes," a "Maybe," or a "No."

 

Slide 22. 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

Speaker Notes:

One or two factors may warrant the use of prefabrication. For example, the fact that the bridge is on an evacuation route may make prefabrication the preferred choice independent of other considerations.

Alternatively, you may want to assign weights to the factors to come up with the decision of whether or not to use prefabrication.

In any case, a majority of "Yes" responses indicates that a prefabricated bridge offers advantages for the specific location under consideration.

 

Slide 23. Considerations in Selecting PBES Categories

  • Rapid Onsite Construction Factors
  • Other Factors
  • Costs Factors

Speaker Notes:

The third section is in a question-and discussion format that is broken into the same three categories of considerations as shown by color-coding on the flowchart and the matrix, i.e., rapid onsite construction, other factors, and costs. This section consists of the same questions as in the flowchart and the matrix, plus additional ones.

 

Slide 24. 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?

Speaker Notes:

Let’s go over the categories in more detail.

The "Rapid Onsite Construction7quot; category includes questions related to...

 

Slide 25. 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.?
 

Slide 26. Considerations in Selecting PBES – Categories

  • Rapid Onsite Construction
  • Other Factors
    • Safety Concerns
    • Environmental Issues
    • Standardization
    • Site Issues

The first category of questions and discussion is "Rapid Onsite Construction." This category is followed by the second category of "Other Factors," which is broken into subcategories of "Safety Concerns," Environmental Issues," "Standardization," and "Site Issues."

 

Slide 27. 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?

Speaker Notes:

The "Other Factors" category includes questions related to safety concerns and environmental issues. Questions related to environmental issues include...

Environmentally sensitive area? (e.g. wetlands, air quality, and noise)
Natural or endangered species? (e.g. fish passage, or peregrine falcon nesting)
Historic bridge?

 

Slide 28. 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?

Speaker Notes:

Also included in the "Other Factors" category are questions related to standardization. Questions related to standardization include...

 

Slide 29. 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?

Speaker Notes:

The last group of questions in the "Other Factors" category relate to site issues. Questions related to site issues include...

 

Slide 30. Considerations Category: Other Factors, cont’d.

  • Accessibility at the site?
  • Prefab foundations & substructures?
  • Formwork & falsework requirements?
  • Straight/skewed/curved alignment?
  • Requires seismic connections?
  • Available connection details?
 

Slide 31. Considerations in Selecting PBES – Categories, cont’d

  • Costs
    • Maintenance of Traffic
    • Contractor’s Operations
    • Owner Agency’s Operations
    • Service Life
  • Availabe Online Resources

Speaker Notes:

The third and final category is "Costs," which is broken into the subcategories "Maintenance of Traffic," "Contractor’s Operations," "Owner Agency’s Operations," and "Service Life."

The framework ends with a brief conclusion paragraph and a listing of available online resources.

 

Slide 32. 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?

Speaker Notes:

The final category is "Costs." This category includes questions related to maintenance of traffic and contractor’s operations. Questions related to maintenance of traffic include...

Questions related to the contractor’s operations include...

 

Slide 32. 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

Speaker Notes:

Also included in the "Costs" category are questions related to the owner agency’s operations, including...

The last subcategory under "Costs" is service life, which includes references to available life-cycle cost evaluation models.

 

Slide 34. FHWA Decision-Making Framework

FHWA  Decision-Making Framework

 

Slide 35. Utah DOT Decision Chart

Utah DOT Decision Chart


Speaker Notes:

See the Utah Case Study Example in the Student Handbook.

A performance goal is for States to include the decision-making framework into their project development process to evaluate ABC-PBES as early in the process as possible, similar to what the State of Utah has done.

 

Slide 36. Framework Available Online

General Information

Publications

  • Framework For PBES Decision-Making

Speaker Notes:

Available online resources are listed at the end of the framework for use in obtaining additional information, including completed prefabricated bridge projects with contact information, publications, research, and a calendar of upcoming events.

The framework is available at this website, which is continually being populated with additional information. We encourage you to visit it often to stay current with the latest developments related to prefabricated bridges.

 

Slide 37. 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)
 

Slide 38. Polling Question #1

Select the items that are ABC Viable Concepts.

  1. Prefabrication of standard elements
  2. Cast-in-place is planned on bridge alignment
  3. Pre-assembly
  4. Off site assembly
  5. Weekend or night time closures are planned.
 

Slide 39. Polling Question #2

Select the obstacles to installing PBES in hours or days.

  1. Lack of education and training
  2. Lack of standards & specifications
  3. Construction industry is geared up for prefab
  4. Potential higher cost & limited resources
  5. Durability is not a concern
 

Slide 40. Polling Question #3

Select the major components of the PBES decision making framework.

  1. Decision-making flowchart
  2. Life cycle cost analysis tool
  3. Decision-making matrix of questions
  4. Decision-making consideration questions and discussions
  5. All of the above
 

Slide 41. Polling Question #4

Select the items that are onsite construction factors.

  1. Low traffic volumes
  2. Emergency repair project on high ADT route
  3. Project has negative impact on major industry
  4. Highway work is on the critical path of project and bridge is not.
  5. There are significant user delays if lane is closed for construction.
 

Slide 42. Polling Question #5

If rapid onsite construction is not required for a project, select the other factors that may make prefabrication the preferred solution.

  1. Bridge is high over the water and near high voltage lines.
  2. Endangered species
  3. Wetlands
  4. Repetitive superstructure spans and substructure types
  5. All of the above
 

Slide 43. 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

Resource Center, Structures TST

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Page last modified on August 14, 2013.
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000