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FHWA ABC Workshop 2009 International Bridge Conference

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FHWA ABC Workshop 2009 International Bridge Conference

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  1. Iowa’s Perspective on ABC Terry Wipf Iowa State University (on behalf of Iowa DOT) FHWA ABC Workshop2009 International Bridge Conference

  2. Local System Precast Motivation • Safety • Traffic flow • Durability • Economics • 20,000 bridges • Limited resources • Cost effective replacement • systems

  3. Precast Bridge Demonstration Project (Local Systems Application)Black Hawk County

  4. Demonstration Bridges • Single span precast modified beam-in-slab bridge • 40 ft span w/ 45 degree skew • 39 ft span w/ 0 degree skew

  5. Goals of Monitoring Program • Evolution of superstructure and substructure elements • Closure pour connection details • Evaluate structural characteristics

  6. Laboratory Testing • Evolution of superstructure and substructure elements • Closure pour connection details • Evaluate structural characteristics

  7. Field Testing and Evaluation • Diagnostic Test • Evaluate in service performance

  8. BackgroundOverview • ABC history in Iowa and evolution • Aware of National ABC agenda…part of overall Iowa DOT research agenda process • FHWA Program Funding IBRC/IBRD/HfL • Key elements for success • Funding • Personnel or office structure • Cooperation with industry (regular basis and good opportunity to discuss ABC) • Standardization (regular process) • National involvement

  9. BackgroundIowa Climate RE ABC • ADT is relatively moderate w.r.t. National • Obstacles • Local construction industry resistance • Cheaper labor rate • No alternative delivery allowed • Culture in Iowa • Precast option is rarely used

  10. BackgroundSummary • Be open to innovation • Start simple and “evolve” • Consider implementing on “Low Volume” roads • Include lab and field testing components (for verification of design assumptions and constructability) • Partner with the industry • Constructability review during design • Hard to get into process…this can be biggest challenge • Involvement nationally: workshops, demo projects, IBRD, HfL, FHWA, other states

  11. Precast Bridge Demonstration Project (Primary/Local Systems Application)Mackey Bridge Boone County

  12. Overview • Design by Iowa DOT • First concerted ABC concept • 3 span pre-stressed girder • 47’-5, 56’-6, 47’-5 Spans • 33’-2 width overall • Precast substructure and superstructure elements

  13. Challenge • Steep learning curve • First use in Iowa – no designer, contractor, fabricator or inspector experience • AASHTO Standard Specification • limited guidance on full depth post-tensioned deck panels • Limited literature and national experience with this style of deck system • The project was let with short lead time for the contractor and fabricator

  14. Goals of Monitoring Program • Evaluate • Structural performance of precast concrete bridge elements in the laboratory • Constructability of connections • Handling of components • Monitor and evaluate structural performance of field bridge during and after construction

  15. Substructure Precast Abutment Footing

  16. Full Depth Deck Panel Fabrication • Pretensioned Transversely • Post-tensioned longitudinally • 32 Interior deck panels • Each ½ bridge width • 4 End panels with PT anchorage zones

  17. Modified LXA beams @ spacing 8’-4

  18. Laboratory Tests

  19. Field Testing and Evaluation • Post-tensioning force in panels • Diagnostic load tests • Evaluate in service performance

  20. Lessons Learned • Critical interaction with industry • More lead time (early letting) for projects of this type with non-standard details • Try to reduce critical path steps • High early strength concrete mix is a key for the project – almost always on the critical path – testing at the manufacturing plant prior

  21. Precast Bridge Demonstration Project (Primary Systems Application)Council Bluffs, IA

  22. Overview • Reconstruct the 24th Street Interchange over I-80 / I-29 • Replace existing structure with a Two-Span CWPG 354’ x 106’ bridge • Use staged construction to maintain one-lane traffic in each direction plus a turning lane • Use ABC techniques

  23. 24th Street - Highways for Life • Application on 24th Street Project – • Full-Depth Precast Deck Panels • High Performance Concrete • High Performance Steel • Structural Health Monitoring • Fully Contained flooded backfill • A+B Bidding • Intelligent Transportation Systems

  24. Challenge • A larger bridge with aesthetic details in a high profile location • Heavy traffic area • New deck panel details, a new contractor and new fabricator NOTE: project went smoothly due to lessons learned on Mackey Bridge • Advantage of trial ABC project in a low pressure area first

  25. Goals of Monitoring Program • Evaluate • Constructability of connections • Handling of components • Monitor and evaluate structural performance of field bridge during and after construction

  26. Full-Depth Precast Deck Panels • Deck is made up of two panels • Pre-tensioned and post-tensioned concrete deck panels • Cast-in-place transverse joint between panels • Cast-in-place longitudinal joint that will tie the two phases of construction • PCC overlay over precast deck panels

  27. Precast Deck Panel Plan View

  28. Deck Panels

  29. Pre-Construction Testing • Investigation of Shear Stud Installation and Testing • Evaluation of Concrete Consolidation in Shear Stud Pocket and Beam Haunch • Evaluation of Joint Shear Transfer

  30. End of Floor Section Longitudinal Closure Pour End of Floor Section

  31. Shear Stud Pocket / Haunch Pour Testing

  32. Joint Tests

  33. Post-Construction Testing • Diagnostic load tests • Deck panel joint performance • Long term structural performance • P/T and pretension reinforcement corrosion

  34. Lessons Learned • Collaboration with the industry prior to design was very important for the success of this project • Preconstruction testing program to evaluate selected items and this was very helpful • Experience gained with many innovations introduced • Lab testing to validate design assumptions prior to construction will reduce risk

  35. Precast Bridge ApproachDemonstration ProjectO’Brien County Iowa 60

  36. Why Precast Concrete Panels? • Expedited construction • Overnight placement • Reduced user cost • Almost immediate exposure to traffic • Controlled Fabrication Conditions • Adequate curing, reduced curling • PPCP Bridge Approaches • Rapid replacement of bridge approaches

  37. Challenge • How take skew into account • How to implement a precast approach • Use for ABC repair (time) • Deteriorated approach slabs • Post tensioning • Grouting • Tie transverse in keyways without match cast • Gain Industry experience • How forces from precast tied to integral abutment would affect bridge

  38. Demonstration Project • Precast Prestressed Bridge Approach Slabs • ~77 ft at either end of a skewed bridge • Tied to integral bridge abutment • 2-way Post-Tensioning • Partial-width panels (lane-by-lane construction) • Installed over crushed aggregate base graded to crown • Panels: 14 ft x 20 ft x 12 in.

  39. 3 spa. @ 20.0' 25.0' 2 spa. @ 14' 6 spa. @ 2.0' Precast Approach Slab Layout Longitudinal PT (1 - 0.6" dia. strands) Transverse PT (1 - 0.6" dia. strands)

  40. Expansion Joint Expansion Joint Approach Slab Integral Abutment Integral Connection Integral Connection Sleeper Slab Precast Girder LXD90 Single Row of HP10x57 Piles Precast Panels Polyethylene Sheet The Companion Bridges Southbound Bridge Schematic Northbound Bridge Schematic

  41. Goals of Monitoring Program • Verify structural performance of PPCP as bridge approach pavement • Joint openings • Bridge movements • Girder flexural behavior • Pile axial/flexural behavior • Provide useful comparison with adjacent CIP bridge approach pavement

  42. Instrumentation Plan NB Bridge

  43. Field • Long-term monitoring • Bridge behavior • Slab behavior • cracking • Abutment behavior

  44. Monitoring Lessons Learned • The two approaches impacted the bridges in different ways • The integral connection between both types of approaches appear to be functioning well • A force exists at the joint between the approach and the mainline pavement

  45. ABC Lessons Learned • Significant experience (Precast/PT) • The forces developed in the slab and bridge are large enough that they need to be considered in the design process • Can take next step for ABC repair under staged construction