Experimental study on failure mode and failure mechanism of multi-box girder bridge under attack of tsunami

Abstract

Comprehensive and intensive understanding to the failure process and failure mechanism of girder bridges is extremely crucial for anti-tsunami design of coastal bridges. The scaled down model of the multi-box girder bridge was manufactured and physical experiments were conducted in the dam-break flume to investigate the failure mode and failure mechanism. Results show that the superstructure can fail in three modes: HM (horizontal movement), HMR (horizontal movement with rotation) and HMRD (horizontal movement with rotation and dropping). And the two variables, namely the exceedance duration and the exceedance impulse, are proposed to analyze the possible failure mode and failure mechanism of the superstructure. The analysis conclusions obtained by the proposed method agree with the failure modes observed in the physical experiments. It is found that transverse horizontal movement of the superstructure always takes precedence over rotation and flow upward. With the increase of incoming tsunami bore height, the risk of failure increases; with the increase of the initial downstream water depth, the exceedance duration and exceedance impulse of horizontal force decreases firstly and then increases, the exceedance duration and exceedance impulse of vertical force and overturning moment increase.