1. Bridge Vulnerabilities Oct 2010

2. What puts bridges at risk? Ability to withstand seismic forces and displacements

4. What puts bridges at risk? Hazard factors (proximity, magnitude, duration…) Site factors (soil conditions e.g. soft saturated soils) Bridge design – Bridges built before 1980 often have inadequate provisions for horizontal loading since modern seismic design codes weren’t adopted until late 1970’s – Structural continuity; redundancy; skewed or curved – Seat width (support length); bearing type (high rockers) – Reinforcing details, especially in reinforced concrete piers – High piers; piers with varying heights Bridge condition – Fatigue; corrosion – Retrofitted? – Flagged? Consequence of failure (lifeline route, high AADT)

5. It’s all in the details.

6. Many of the following examples are from Hurricane Katrina but the concept is the same.

7. Shear blocks provides lateral restraint

8. Lateral forces can move entire spans This and other examples are from Hurricane Katrina but the principle is the same.

9. Displaced Joint

10. “Pounding” from longitudinal movement

11. Pedestals provided lateral restraint

12. Support Length

13. Dropped Spans

14. Lateral Shift

15. Column Retrofit (Steel jackets & FRP Wraps)

16. Open Finger Joints

17. Unreinforced & Masonry Abutments

18. Floor Beam Hanger Detail