Influence of pounding buffer zone for mitigation of seismic response of curved bridges

Abstract

It is well-known that seismic pounding is detrimental to curved bridges since it can not only amplify the global displacement demands of the bridge deck but also cause stress concentration and localized damage to the bridge components like abutment backwall and expansion joints. In this study, a shake table experiment was performed on a 1/25 scale curved bridge model with a pounding buffer zone made of natural rubber pad or aluminum foam at the expansion joint location to mitigate the pounding effect. This model consisted of a single-span segment, a two-span segment and an expansion joint in-between. For comparison purpose, the buffer zone was also made of steel in order to achieve a steel-on-steel interaction. Two historical ground motions including a pulse-type near-field motion and a non-pulse type near field motion, were selected to excite the bridge model to study the effects of motion characteristics. The results show that the buffer zones of rubber and aluminum can effectively reduce seismic impact forces, and hence alleviate the localized damage. Meanwhile, these two buffer zones can also effectively reduce the global response of the bridge such as bridge deck accelerations, seat width demand at the joint location, and in-plane rotation of the bridge deck. However, when comparing with the aluminum foam, the rubber buffer zone demonstrated better performance in reducing the pounding force, bridge deck accelerations, and seat width demand at the expansion joint locations. In addition, for the same bridge model, the pulse-like record can result in significantly large response than the nonpulse-like record, regardless of the buffer zone materials. It was also found that seismic collision of the curved bridge could also induce significantly large friction force along the contact surface, which could also influence the response of the bridge system.