近断层脉冲型地震动作用下高墩连续刚构桥振动台试验研究

    Experimental Research on the Seismic Response of a Continuous Rigid Frame Bridge With High Piers Under Near-fault Pulse-like Ground Motions

    • 摘要: 为了研究近断层脉冲型地震动对高墩连续刚构桥抗震性能的影响,以某典型高墩连续刚构桥为原型,设计制作了该桥的1/15缩尺试验模型,利用多子台模拟地震动振动台台阵系统,完成了远场地震动和近断层地震动输入下的对比试验,重点探讨了近断层地震动速度脉冲效应及脉冲个数的影响.研究结果表明:高墩连续刚构桥纵向和横向一阶频率均较小,结构地震响应主要以低频成分为主;近断层脉冲型地震动作用下模型桥的地震响应均大于远场地震动作用下模型桥地震响应的2倍,而近断层无脉冲地震动下模型桥的动力响应略小于远场地震动输入时模型桥的动力响应,为其0.76~0.95;速度脉冲效应使高柔的高墩连续刚构桥主梁瞬时产生较大位移响应(最大值为54.8 mm),极易引起主梁端部碰撞和支座破坏,在抗震设计上应引起重视;速度脉冲个数对高墩连续刚构桥地震响应的影响显著,墩顶位移响应脉冲个数影响系数AFw为1.46~5.54,其中,多脉冲型地震动作用下模型桥的动力响应最大,单脉冲型地震动作用下模型桥的动力响应次之,而双脉冲型地震动引起的结构响应相对较小.因此,对靠近断层区域的此类桥梁,应考虑近断层地震动速度脉冲效应及其参数变化的影响.

       

      Abstract: To study the effects of near-fault pulse-type (NFPT) ground motions on seismic response of a continuous rigid frame bridges with high piers (CRFB-HP), a 1/15-scale model was designed and fabricated. Then series of shaking table tests were carried out to study the seismic response of the model under the far field ground motions and NFPT ground motions, respectively. The effects of the velocity pulse number (VPN) were mainly discussed. Results show that the first-order vibration frequencies of the model bridge along the longitudinal and transverse directions are relatively small. The seismic response of the model is mainly low frequency response. The seismic response of the bridge model under the NFPT ground motions is greater than that of twice of it under the far-field ground motions. However, the dynamic response of the bridge model under the no-pulse near-fault ground motions is slightly smaller than (0.76-0.95 times as large as) that of the far-field ground motions. The velocity pulse causes instantaneously large displacement response of the model, the peak value is up to 54.8 m. In this sense, the collision between the abutment and the girder or the bearing damage may occur. The VPN has a significant influence on the seismic response of the bridge model, and the influence coefficient of the VPN (AFw) is between 1.46-5.54. The multi-pulse ground motions may cause larger dynamic response of the model than the others. The double-pulse ground motion has much smaller influence on the dynamic responses of the model bridge. The parameters influence of the NFPT ground motions on the seismic response of the long-period bridges should be considered.

       

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