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Bridge Vulnerabilities. Oct 2010. What puts bridges at risk?. Ability to withstand seismic forces and displacements. What puts bridges at risk?. Hazard factors (proximity, magnitude, duration…) Site factors (soil conditions e.g. soft saturated soils) Bridge design
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Bridge Vulnerabilities Oct 2010
What puts bridges at risk? • Ability to withstand seismic forces and displacements
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)
Many of the following examples are from Hurricane Katrina but the concept is the same.
Shear blocks provides lateral restraint 7 Sept 2005 (85) OConnor 17Oct (137)
Lateral forces can move entire spans 8Sept2005 (8) This and other examples are from Hurricane Katrina but the principle is the same.
Displaced Joint 8Sept2005 (12)
“Pounding”from longitudinal movement 8Sept2005 (16)
Pedestals provided lateral restraint 8Sept2005 (43)
Support Length 8Sept2005 (44)
Dropped Spans 8Sept2005 (62)
Lateral Shift OConnor 19Oct (54)
