中文摘要：

以一座钢悬索桥为对象,首先建立能考虑主缆和吊索振动松弛的全桥空间有限元模型,所得固有振动模态与数值解析模态、现场试验结果的比较验证了有限元模型的正确性,可采用该模型进行非线性地震响应分析。其次,探讨地震荷载下主缆和吊索发生振动松弛的可能性,结果表明：强震作用于纵桥向时,跨中附近的吊索会出现振动松弛,但初始轴力较大、轴力减小量相对较小的主缆没有出现振动松弛;强震作用于横桥向时,吊索和主缆均未出现振动松弛。最后,分析强震荷载下吊索振动松弛对悬索桥各构件的影响,结果表明：纵桥向加震时,吊索振动松弛使横桥向另一侧的吊索轴力增大10%,但对加劲梁、主塔和主缆的地震响应影响较小,最大增大5%。

英文摘要：

The three dimensional finite element model of a steel suspension bridge,considering vibration loosening of the main cables and hangers, was established. This model, verified by comparing with those from numerical analysis and field test,can be applied to analyzing the nonlinear seismic response of the bridge. Then,loosening possibility of main cables and hangers under earthquake was discussed. It is showed that,some hangers near the mid-span loosen under longitudinal strong earthquake,while no vibration loosening is founded in the main cables,with the axial force of large initial value and relatively small reduction. Moreover,no hanger or main cable vibrates loosely under lateral strong earthquake. The influence of hanger vibration loosening on the bridge members under strong earthquake was analyzed. The results show that the axial force of hanger increases by 10%, due to the vibration loosening in the corresponding lateral hangers under longitudinal loads. However,the internal force of the girder,tower and main cables increases by lessthan 5%.