1. Precast Bent System for Bridges in Seismic Regions
Marc Eberhard, John Stanton
Olafur Haraldsson, Todd Janes, Hung Viet Tran
University of Washington
NEES & PEER Annual Meeting
San Francisco, 8 -9 October 2010

2. Acknowledgments WSDOT TRANSNOW Valle Foundation
FHWA, Highways for Life Program
PEER

3. Background Accelerate on-site bridge construction.
Use precast concrete components.
Connection details:
seismic-resistant
construct

4. Construction Procedure
1) Excavate footing.

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

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

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

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

9. Connections CIP RC (ref) Precast RC Precast Prestressed Cap-Beam
to Column
Column to
Spread Footing
Column to
Drilled Shaft

10. Column-to-Cap-Beam Connection
Thank you for your time. We’d like to thank Vince Chaijaroen, Wayne Brown, Amanda Jellin, Jon Padavorac, and the help in the structures lab. We’d especially like to thank WSDOT for their support and generous funding of this research effort. Questions???

11. Cap Beam Connection: Many small bars and ducts
Courtesy: BERGER/ABAM Engineers
Tight tolerances.

12. Cap-Beam Connection: Large bars
Precast column
Precast cap beam
6 # 18 rebar
8.5” corrugated steel ducts
High strength grout
The proposed precast bridge bent connection features: 12

13. Cap-Beam Connection: Conclusions Failure occurs in the column.
Large-bar precast connection behaves the same as a cast-in-place connection.
All 4 specimens were subjected to the same lateral displacement history. The tests revealed all 4 specimens to have the same hysteretic performance, despite debonding of the bars or having distributed reinforcement. Specimen REF did exhibit a delay of bar fracture, but loss of lateral capacity was similar. 13

14. Column-to-Footing Connection
Thank you for your time. We’d like to thank Vince Chaijaroen, Wayne Brown, Amanda Jellin, Jon Padavorac, and the help in the structures lab. We’d especially like to thank WSDOT for their support and generous funding of this research effort. Questions???

15. Footing Connection: Construction
Headed bars

16. Footing Connection: Headed Bars
Strut and Tie Model.

17. Footing Connection Hooked bars facing out (Conventional cip)
Load transfer is tangential to hook.
Ineffective!

18. Footing Connection: Construction

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

20. Spread Footing Connection: Test
After seismic testing. Foundation undamaged.

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

22. Spread Footing Connection
Constructability:
Column has no projecting bars.
No “form-savers”.
Easy to fabricate and transport.
From constructability point of view we have good connection. No bars going between precast column and cast in place footing. We are able to produce linear element that is easy to transport.
If we look at the seismic performance. Using terminators we get better anchorage than hooked bars facing outwards.
Today's code require fair amount stirrups to prevent shear failure. AASHTO also implies the need for shear friction steel.
But the biggest question is can we reduce it or eliminate them to make the construction easier and faster.

23. Spread Footing Connection
Structural Performance:
Terminators provide better anchorage than hooked bars facing outwards.
Failure in column. Footing undamaged in lateral load and vertical load tests.
Seismic performance as good as, or better than, conventional c.i.p. construction.
From constructability point of view we have good connection. No bars going between precast column and cast in place footing. We are able to produce linear element that is easy to transport.
If we look at the seismic performance. Using terminators we get better anchorage than hooked bars facing outwards.
Today's code require fair amount stirrups to prevent shear failure. AASHTO also implies the need for shear friction steel.
But the biggest question is can we reduce it or eliminate them to make the construction easier and faster.

24. Implementation
Bid Opening:
October 14th

25. Pre-Tensioned System
Thank you for your time. We’d like to thank Vince Chaijaroen, Wayne Brown, Amanda Jellin, Jon Padavorac, and the help in the structures lab. We’d especially like to thank WSDOT for their support and generous funding of this research effort. Questions???

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

27. Pre-Tensioned System
Pre-tensioning solves corrosion problems perceived to exist in post-tensioning.
Pre-tension in a plant.
Good QC.
Special equipment and extra site time for post-tensioning are not needed.
Can add rebars for energy dissipation.

28. Thank You
Thank you for your time. We’d like to thank Vince Chaijaroen, Wayne Brown, Amanda Jellin, Jon Padavorac, and the help in the structures lab. We’d especially like to thank WSDOT for their support and generous funding of this research effort. Questions???