Performance-Based Seismic Assessment of Skewed Bridges

1. Performance-Based Seismic Assessment of Skewed Bridges PEER by ErtugrulTaciroglu, UCLA FarzinZareian, UCI PEER Transportation Systems Research Program

2. Collaborators Students PeymanKhaliliTehrani, UCLA PeymanKaviani, UCI Ali Nojoumi, UCLA PerePla-Junca, UCI MajidSarraf, PARSONS AnooshShamsabadi, Caltrans

3. Outline • Skew bridges & project goals • Modeling skew abutment response • Developing NLTH simulation models for skew bridges • Exploring and quantifying skew-bridge response • Discussion

4. General Problem Performance assessment of skewed abutment bridges • Appropriate modeling of bridge superstructure. • Appropriate modeling of bridge abutment. • Selection of appropriate input ground motions.

5. Previous Studies Straight Abutment: Aviram, Mackie, and Stojadinovic 2008 Johnson et al. (2009), Kotsoglou and Pantazopoulou (2010), Mackie and Stojadinovic (2007), Paraskeva et al. (2006) Skewed Abutment: Abdel-Mohti and Pekcan (2008) Meng and Lui (2000), Maragakis (1984), Wakefield et al. (1991), Ghobarah and Tso (1974)

6. Ground Motions • Three sets of GMs were selected by the PEER Transportation Research Program • 40 GMs per set • Three types of GMs: Pulse-like, soil-site, and rock-site • Fault Normal: longitudinal direction; Fault parallel: transverse direction • The GMs are from mid- to large-magnitude • Near-source GMs • Selected GMs have a variety of spectral shapes, durations, and directivity periods Fault-Normal 3.0 3.0 3.0 3.0 3.0 3.0 2.0 2.0 2.0 2.0 2.0 2.0 Fault-Parallel 1.0 1.0 1.0 1.0 1.0 1.0 Soil-Site Pulse-Like Rock-Site 2.0 2.0 2.0 2.0 2.0 2.0 4.0 4.0 4.0 4.0 4.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0

7. plan view Anatomy of an Abutment Seat-type There are also “monolithic abutments”

8. Skew Bridge Challenges • Unseating • Shear key failure • Backfill response (near field) • Deck rotation (esp. for single span bridges) • High seismic demands on columns

9. Skew Bridge Challenges • Unseating • Shear key failure • Backfill response (near field) • Deck rotation (esp. for single span bridges) • High seismic demands on columns

10. Skew Bridge Challenges • Unseating • Shear key failure • Backfill response (near field) • Deck rotation (esp. for single span bridges) • High seismic demands on columns

11. Skew Bridge Challenges • Unseating • Shear key failure • Backfill response (near field) • Deck rotation (esp. for single span bridges) • High seismic demands on columns

12. Skew Bridge Challenges • Unseating • Shear key failure • Backfill response (near field) • Deck rotation (esp. for single span bridges) • High seismic demands on columns

13. Skew Bridge Challenges • Unseating • Shear key failure • Backfill response (near field) • Deck rotation (esp. for single span bridges) • High seismic demands on columns

14. Skew-angled Abutments Skew happens ? ?

15. Abutment Modeling Input parameters for “Hardening Soil” PLAXIS model Lnom

16. Abutment Modeling Lskew ≠ Lnom

17. skew abutment with deck-width wr skew abutment with wall-width wr Abutment Modeling straight abutment with wall-width wr

18. Bridge Modeling The Jack Tone Road On-Ramp Overcrossing The La Veta Avenue Overcrossing The Jack Tone Road Overhead

19. Bridge Matrix

20. Abutment Modeling a a a a Simplified Model Dual-Rigid Model Friction Model Skewed Model

21. Abutment Modeling

22. Shear Key Modeling Bridge “C” Bridge “B” Bridge “A” VN,A= 755 kips VN,B= 1810 kips VN,C= 2360 kips

23. Deck Rotation – Bridge A Old Models Bridge “A”, Lower, Symt.:

24. Column Drift Ratio – Bridge A Old Models Bridge “A”, Lower, Sym.

25. Column Drift Ratio – Bridge B Old Models Bridge “B”, Lower, Sym.

26. Deck Rotation – Bridge A Median Response, Bridge “A”, Lower, Symt.

27. Deck Rotation – Bridge A Median Response, Bridge “A”, Lower, Symt. NO SHEAR KEY MODELED

28. Column Drift Ratio – Bridge A Median Response, Bridge “A”, Lower, Symt.

29. Column Drift Ratio – Bridge A Median Response, Bridge “A”, Lower, Symt. NO SHEAR KEY MODELED

30. Deck Rotation – Bridge A Pulse 1, Bridge “A”, Lower, Symt.

31. Column Drift Ratio – Bridge A Pulse 1, Bridge “A”, Lower, Symt.

32. Probability of Collapse – Bridge A 15% 15% 15% 10% 10% 10% Skew Angle = 0o Skew Angle = 30o Skew Angle = 60o Bridge “A”, Lower, Symt.

33. Deck Rotation – Bridge B Median Response, Bridge “B”, Lower, Symt.

34. Column Drift Ratio – Bridge B Median Response, Bridge “B”, Lower, Symt.

35. Probability of Collapse – Bridge B 38% 38% 38% 25% 25% 25% Skew Angle = 0o Skew Angle = 30o Skew Angle = 60o Bridge “B”, Lower, Symt.,

36. Shear Key Performance – Bridge A Number of Failed Shear Keys out of 40 0 30 60 Abutment Skew Angle 90 Intercept Angle 120 150

37. Shear Key Performance – Bridge B Number of Failed Shear Keys out of 40 0 30 60 Abutment Skew Angle 90 Intercept Angle 120 150

38. Next Steps – August Meeting • Develop a three-DOF macro-element through numerical simulations with 3D continuum FE models and analytical considerations for torsionally flexible bridges. • Finalize the bridge models including the new abutment model. • Rotate Ground motions? • Quantify the Sensitivity of Skew Bridge Response and Damage Metrics to Key Input Parameters • Update Caltrans Seismic Design Criteria for Skew-Angled Bridges

39. Next Steps – This Meeting • Develop a three-DOF macro-element through numerical simulations with 3D continuum FE models and analytical considerations for torsionally flexible bridges. • Finalize the bridge models including the new abutment model. • Rotate Ground motions? • Quantify the Sensitivity of Skew Bridge Response and Damage Metrics to Key Input Parameters • Update Caltrans Seismic Design Criteria for Skew-Angled Bridges