中文摘要：

为研究具有破裂前方效应和滑冲效应的2类脉冲型地震动对超大跨斜拉桥不利响应的影响,提出近断层脉冲型地震动合成的＂分解-叠加＂新方法,从频谱特性及结构地震响应两方面对该方法的有效性进行了验证。以苏通长江公路大桥为研究对象,分析了脉冲周期、脉冲速度峰值、脉冲数等参数对超大跨斜拉桥地震响应的影响规律。结果表明：近断层地震动高频成分对结构的响应不容忽视,＂分解-叠加＂法能够反映近断层地震动高频成分及低频脉冲成分对结构响应的贡献;具有滑冲效应的低峰值脉冲可激起主塔的高阶阵型,破裂前方效应地震动主要激起主塔的基本振型;当破裂前方效应和滑冲效应复合作用且两者同时达到脉冲峰值时,结构地震响应最为显著;脉冲速度峰值对斜拉桥主塔内力和位移等响应影响显著;不同脉冲周期的地震动作用下,滑冲效应引起斜拉桥地震响应明显高于破裂前方效应;脉冲个数为奇数的地震动较偶数的地震动对结构响应影响更为显著。

英文摘要：

In order to investigate the seismic response of a super-span cable-stayed bridge subjected to 2 types of pulse-type ground motions with forward-directivity effect and fling-step effect, the new method, namely ＂decomposition-incorporation method＂ was proposed and its validity was verified by the spectrum characteristics and the structural seismic responses. Taking Sutong Bridge as an example, the influences of parameters including the pulse duration, pluse peak velocity and numbers of pulse on the seismic response of super-span cable-stayed bridge were investigated. The results show that the high frequency components of near-fault ground motions have a significant effect on the response of structure and the proposed method is capable of representing the effects of the high frequency components and low frequency pulse components in near-fault ground motions on structural seismic response. Low-peak pulse records with fling-step effects can excite the main towers primarily in their high mode, while ground motions with forward directivity effects can excite their fundamental mode of main towers. The seismic response of the structure is significant when the forward-directivity effect and fling-step effect are combined to reach the peak value at the same time. The pulse peak velocity has significant effect on the responses of main tower＇s stress and displacement of cable-stayed bridges. Records with fling-step effects under different pulse durations impose a larger response to the bridge compared to records with forward-directivity effects. The influences of ground motions with odd-numbered pulse-type wave peak on seismic response are more significant than that with even-numbered pulse-type wave peak.