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PBES Seismic Research at the University of Washington John Stanton, Marc Eberhard, Kyle Steuck, Jason Pang, Todd Janes, Olafur Haraldsson, Hung Viet Tran,

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Presentation on theme: "PBES Seismic Research at the University of Washington John Stanton, Marc Eberhard, Kyle Steuck, Jason Pang, Todd Janes, Olafur Haraldsson, Hung Viet Tran,"— Presentation transcript:

1 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, Seattle,

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

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

4 Objective Develop a family of seismic bridge PBES connections for: Rapid construction Rapid construction Superior seismic performance 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 2) Position and brace precast column. Construction Procedure

10 3) Place footing reinforcement and cast. Construction Procedure

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

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

13 Precastprestressedc.i.p. RC (ref) PrecastRCCap-beam to column Column to spread footing spread footing Column to drilled shaft drilled shaftConnectionDetails

14 Precastprestressedc.i.p. RC (ref) PrecastRCCap-beam to column Column to spread footing spread footing Column to drilled shaft drilled shaftConnectionDetails

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

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

17 Large-Bar Connection Cyclic Lateral Load Testing

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

19 Precastprestressedc.i.p. RC (ref) PrecastRCCap-beam to column Column to spread footing spread footing Column to drilled shaft drilled shaftConnectionDetails

20 Footing Connection: Construction Headed bars

21 Performance 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 Constructability: Column has no projecting bars.Column has no projecting bars. No “form-savers”.No “form-savers”. Easy to fabricate and transport.Easy to fabricate and transport. Note: Top steel not yet in place

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

26 Precastprestressedc.i.p. RC (ref) PrecastRCCap-beam to column Column to spread footing spread footing Column to drilled shaft drilled shaftConnectionDetails

27 Drilled-Shaft Connection

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29 DS-1 DS-2

30 Drilled-Shaft Connection Performance depends on spiral in transition region. 100% c.i.p. spiral  failure in column.100% c.i.p. spiral  failure in column. 50% c.i.p. spiral  failure in transition.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.Third drilled shaft specimen (in lab now) has thin concrete in transition region.

31 Precastprestressedc.i.p. RC (ref) PrecastRCCap-beam to column Column to spread footing spread footing Column to drilled shaft drilled shaftConnectionDetails

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

33 Pre-Tensioned System 1.Pre-tensioning solves corrosion problems perceived to exist in post-tensioning. 2.Pre-tension in a plant. Good QC.Good QC. No special equipment or extra site time needed (compare with post-tensioning).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 strand c.i.p. footing Bonded rebar Cracking plane

35 Test Specimens Footing specimen Cap beam specimen

36 Test Specimens - Footing connection

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

38 2% drift

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

40 Preliminary Results 1. System re-centers. 2. No strands broke. 3. 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: New pre-tensioned specimen in lab now: 1.Use HyFRC (Hybrid fiber reinforced concrete) in the plastic hinge zone to reduce crushing. 2.Use stainless steel rebars to increase drift capacity and energy dissipation.

42 Thank You

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47 Background Accelerate on-site bridge construction. Use precast concrete components. Connection details: seismic-resistantconstruct

48 Column-to-Cap-Beam Connection

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

50 Column-to-Footing Connection

51 Pre-Tensioned System

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57 2% drift

58 6% drift

59 Spread Footing Connection after seismic testing Foundation undamaged. Foundation undamaged.

60 Spread Footing Connection – Gravity Load Test (Damaged) column crushed at: 3.5 * (1.25DL LL). No damage to footing. No sign of punching failure.

61 SF-1 H f /D c = 1 Slots in column base More diagonal rft. 100% Caltrans stirrups SF-2 H f /D c = 1 No slots Less diagonal rft. 50% Caltrans stirrups

62 Spread Footing Thickness SF-1 and SF-2. H foot = D col SF-3. H foot = 0.5 D col

63 SF-1 H f /D c = 1.0 Slots in column base More diagonal rft. 100% Caltrans stirrups SF-3 H f /D c = 0.5 No slots Less diagonal rft. Heavy beam shear reinforcement

64 SF Movie

65 After testing. SF-3

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67 DS-1 100% transverse reinforcement in transition region DS-2 50% transverse reinforcement in transition region

68 Next Steps: Next Steps: 1.Test pretensioned, cap-beam specimen. 2. Bond tests on epoxy-coated strand. 3. Data analysis and design methodologies. Looking Forward: 1. Methodology calibration tests (Grouted ducts, spread footings, drilled shafts) 2.High-performance materials (e.g. ECC at rocking interface).

69 Precastprestressedc.i.p. RC (ref) PrecastRCCap-beam to column Column to spread footing spread footing Column to drilled shaft drilled shaftConnectionDetails NEXT !


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