Lessons Learned from the Damaged Huilan Interchange in the 2008 Wenchuan Earthquake

A disastrous earthquake struck Wenchuan in China’s Sichuan province in 2008 and caused heavy casualties and structural damage to bridges and buildings. One of the two severely earthquake-damaged curved bridges in China, the Huilan interchange, had been carefully studied, including postearthquake investigation and identification of the cause of failure for this bridge. The Huilan interchange, constructed in 2004 in Mianzhu City, consisted of a viaduct and four horizontally circular ramp bridges with continuous box girders. Field investigations found that the seismic damage to the ramp bridges was especially heavy, one or two short piers in all, but one of the ramp bridges experienced severe failure, and the box girders over the failed piers were fractured. Other piers of the ramp bridges suffered minor-to-moderate damage, including concrete cover spalling, concrete cracking, and slippage damage of the rubber bearings. The viaduct suffered only slight damage, including slippage damage of the rubber bearings and pounding damage of the superstructure. The seismic performance of the bridge was evaluated by finite-element modeling and compared with field observations. It was found that the bearing on top of the shortest pier, Pier 1, was damaged first. Then, the seismic action was concentrated on the next shortest pier, Pier 2, which had the largest flexural stiffness. Pier 2 first yielded in flexure, and, as the lateral displacement increased, the ultimate response of this pier was dominated by its shear capacity, and it eventually failed in flexure-shear mode.