Presentation on theme: "PREFABRICATED BRIDGE ELEMENTS & SYSTEMS (PBES), DECISION- MAKING FRAMEWORK Claude Napier Sr. Structural Engineer Resource Center - Structures TST."— Presentation transcript:
PREFABRICATED BRIDGE ELEMENTS & SYSTEMS (PBES), DECISION- MAKING FRAMEWORK Claude Napier Sr. Structural Engineer Resource 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 2
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 3
Learning Outcomes List and define the different costs factors influencing the PBES decision Be a champion to promote PBES Technology 4
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 5
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 6
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 7
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 Construction Survey 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 Construction Survey to Sample State Bridge Engineers
Framework for PBES Decision-Making Users Decision makers for bridge type Implementers – Designers – Project Managers
Framework for PBES Decision-Making – Format Introduction Flowchart – Decision-Making at a Glance Matrix – Decision-Making Questions Decision-Making Considerations – Questions with Discussion and References
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
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 ?
Decision-Making Matrix Example Questions QuestionYesMaybeNo 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
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 elements b.Cast-in-place is planned on bridge alignment c.Pre-assembly d.Off site assembly e.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 training b.Lack of standards & specifications c.Construction industry is geared up for prefab d.Potential higher cost & limited resources e.Durability is not a concern
Polling Question #3 Select the major components of the PBES decision making framework. a.Decision-making flowchart b.Life cycle cost analysis tool c.Decision-making matrix of questions d.Decision-making consideration questions and discussions e.All of the above
Polling Question #4 Select the items that are onsite construction factors. a.Low traffic volumes b.Emergency repair project on high ADT route c.Project has negative impact on major industry d.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 species c.Wetlands d.Repetitive superstructure spans and substructure types e.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, firstname.lastname@example.org@dot.gov Louis Triandafilou, Senior Structural Engineer 410-962-3648, email@example.com@dot.gov Resource Center, Structures TST