Performance of Modern Highway Bridges in the 2016 Kaikoura Earthquake

Abstract

The performance assessment of four highway bridges damaged in the 2016 Kaikoura Earthquake is presented and methods adopted to repair the damage are outlined. The oldest of the four bridges was designed in 1969–70 and the newest in 2004. Although earthquake design procedures have advanced over this period, the design earthquake loadings for all four bridges were based on acceleration response spectra and the bridges detailed to have ductile failure modes in pier columns with circular sections. Levels of damage in the plastic hinges were predicted by undertaking back-analysis using static and dynamic analyses based on the ground motions recorded at strong-motion recording stations located within 1.5–7 km of the bridge sites. The response displacement of one of the bridges was considerably greater than its damage control limit state displacement. This explained the severe damage observed in the plastic hinges of this bridge. Significant plastic straining occurred in the plastic hinge reinforcement on two of the other bridges and the remaining low-cycle fatigue capacity of the column reinforcement was estimated using non-linear time history analyses. Column strengthening was required on one of these bridges and repairs without strengthening were found to be satisfactory on the other bridge.