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PBES Seismic Research at the University of Washington

PBES Seismic Research at the University of Washington. John Stanton , Marc Eberhard , Kyle Steuck , Jason Pang, Todd Janes , Olafur Haraldsson , Hung Viet Tran, Phillip Davis , Gunnsteinn Finnsson , Jeffrey Schaefer. University of Washington. FHWA P2P Exchange Workshop,

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PBES Seismic Research at the University of Washington

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  1. PBES Seismic Research at the University of Washington John Stanton, Marc Eberhard, Kyle Steuck, Jason Pang, Todd Janes, OlafurHaraldsson, Hung Viet Tran, Phillip Davis, GunnsteinnFinnsson, Jeffrey Schaefer. University of Washington FHWA P2P Exchange Workshop, Seattle, 2011.11.15

  2. Partners • WSDOT • Berger-ABAM • Concrete Technology Corporation • Tri-state Construction

  3. Acknowledgments • FHWA (Highways for Life) • WSDOT • PEER • TransNOW • Valle Foundation • PacTrans • NSF-NEES

  4. Objective • Develop a family of seismic bridge PBES connections for: • Rapid construction • Superior seismic performance Designers can mix and match connections to suit local conditions.

  5. Key Elements 1. Large bars grouted in ducts. (Rapid construction)

  6. Key Elements 2. Socket connections. (Rapid construction)

  7. Key Elements 3. Unbonded pre-tensioned columns. (Seismic performance)

  8. Construction Procedure 1) Excavate footing.

  9. Construction Procedure 2) Position and brace precast column.

  10. Construction Procedure 3) Place footing reinforcement and cast.

  11. Construction Procedure • Set cap-beam, grout bars into ducts.

  12. Construction Procedure 5) Place girders, diaphragms and deck.

  13. Connection Details c.i.p. RC (ref) Precast RC Precast prestressed Cap-beam to column Column to spread footing Column to drilled shaft

  14. Connection Details c.i.p. RC (ref) Precast RC Precast prestressed Cap-beam to column Column to spread footing Column to drilled shaft

  15. Large Bar Connection (Cap Beam) • Bars grouted into ducts. • Few, large bars simplify fit-up. • Is development length a problem?

  16. Large Bar Connection (Cap Beam)#18 Bar Anchorage Tests • Pullout tests. • Need 6db to develop yield, 10db to develop fracture. • Bar can easily be anchored within cap beam.

  17. Large-Bar Connection Cyclic Lateral Load Testing

  18. Large-Bar Connection Cyclic Lateral Load Testing • Failure occurs in the column. • PC Connection behaves the same as c.i.p.

  19. Connection Details c.i.p. RC (ref) Precast RC Precast prestressed Cap-beam to column Column to spread footing Column to drilled shaft

  20. Footing Connection: Construction Headed bars

  21. Footing Connection - Performance Headed bars provide good load transfer. Internal forces: Strut and Tie Model.

  22. Footing Connection Hooked bars facing out (Conventional cip) Load transfer is tangential to hook. Poor transfer.

  23. Spread Footing Connection Vertical (gravity) load. Lateral (seismic) load.

  24. Spread Footing Connection Note: Top steel not yet in place Constructability: • Column has no projecting bars. • No “form-savers”. • Easy to fabricate and transport.

  25. Spread Footing Connection Structural Performance • Terminators provide better anchorage than hooked bars facing outwards. • Failure occurs in column, not footing. • Seismic performance as good as, or better than, conventional c.i.p. construction.

  26. Connection Details c.i.p. RC (ref) Precast RC Precast prestressed Cap-beam to column Column to spread footing Column to drilled shaft

  27. Drilled-Shaft Connection

  28. Drilled-Shaft Connection

  29. DS-1 • DS-2

  30. Drilled-Shaft Connection Performance depends on spiral in transition region. • 100% c.i.p. spiral  failure in column. • 50% c.i.p. spiral failure in transition. Hoop tension strength of transition region concrete appears to be important. • Third drilled shaft specimen (in lab now) has thin concrete in transition region.

  31. Connection Details c.i.p. RC (ref) Precast RC Precast prestressed Cap-beam to column Column to spread footing Column to drilled shaft

  32. Background Self-centering structural systems • Unbondedprestressing tendons for elastic restoring force. • Yielding steel for energy dissipation.

  33. Pre-Tensioned System • Pre-tensioning solves corrosion problems perceived to exist in post-tensioning. • Pre-tension in a plant. • Good QC. • No special equipment or extra site time needed (compare with post-tensioning). • 3. Can add rebars for energy dissipation.

  34. Pre-Tensioned System PC cap-beam Sleeved strand Bonded rebar Cracking plane Bonded strand c.i.p. footing

  35. Test Specimens Cap beam specimen Footing specimen

  36. Test Specimens - Footing connection

  37. Test Specimens- Footing details Strand sleeve Screw-thread adjustment device Bonded region Load cell Strand chuck Void under column

  38. 2% drift

  39. Load vs. Displacement RC: does not re-center UBPT: re-centers

  40. Preliminary Results • System re-centers. • No strands broke. • No loss of strand bond. • 5. Damage to concrete at interface, possibly promoted by stub bars from footing.

  41. New pre-tensioned specimen in lab now: • Use HyFRC (Hybrid fiber reinforced concrete) in the plastic hinge zone to reduce crushing. • Use stainless steel rebars to increase drift capacity and energy dissipation.

  42. Thank You

  43. Background • Accelerate on-site bridgeconstruction. • Use precast concrete components. • Connection details: • seismic-resistant • construct

  44. Column-to-Cap-BeamConnection

  45. Precast column Precast cap beam 6 # 18 rebar 8.5” corrugated steel ducts High strength grout Cap-Beam Connection:Large bars

  46. Column-to-FootingConnection

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