Seismic Performance of Highway Bridges

The 921 Taiwan Chi-Chi earthquake incurred tremendous disaster to the central region of the island, particularly to Taichung and Nantou counties. Most of the bridges on the provincial and county routes in Taichung, Nantou, Changhua, and Yunlin counties escaped from serious damage, while approximately 20% of them suffered minor-to-major damage. The construction completion dates of those bridges range from 1960 through 1999. Damage to these bridges include fault rupturing, collapsed spans, landslides, soil settlement, slope failures, flexural and/or shear failures, and liquefaction. This paper begins with a brief description on the evolution of seismic design code for bridges in Taiwan, followed by a general depiction of the performance of highway bridges located in the four counties during the earthquake. Several major damaged bridges with typical damage modes are illustrated and explored. Lessons learned from the field observations and suggestions made on research needs are also discussed.