Bridge Foundation Behavior In Alaska Earthquake

Extensive damage was sustained by highway bridges with a wide variety of foundation types located within 80 miles of the zone of energy release of the 1964 Alaska earthquake. Data on foundation conditions, bridge and channel configurations, and foundation displacements have been collected and analyzed to asses the effects of foundation-support conditions on bridge performance during the earthquake. Bridges founded wholly on bedrock sustained little or no foundation displacement. The greatest concentrations of severe damage occurred in thick deposits of saturated cohesionless soils; ample evidence of soil liquefaction was found in these materials. Bridge foundations in saturated sands and silts sustained severe displacement even where the average standard penetration resistance of the upper 30 ft of soil was as high as 25 blows per foot. Broad recommendations are offered for precluding bridge damage of this type during major earthquakes.