山区大跨度混合梁独塔斜拉桥的合理横向减震体系
Reasonable Transverse Isolation System for Long-span Single-tower Cable-stayed Bridges with Hybrid Girders in Mountainous Areas
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摘要: 针对适合山区河谷地形的典型大跨度混合梁独塔斜拉桥的合理横向减震体系,以金沙江特大桥为工程背景,分析了结构的显著非对称特征、动力特性及地震响应规律.提出了基于影响矩阵的减震体系阻尼器合理参数的计算方法,并以三角形钢阻尼器为例,探讨了其收敛性及影响因素.结果显示:大跨度混合梁独塔斜拉桥横向减震体系下各位置处的阻尼器合理屈服力与相应横向固定体系的支座剪力之间存在着明显的相关性,采用合适的阻尼器初始屈服力和影响矩阵可以有效地提高迭代计算的速度和稳定性.基于辅助墩与边墩的刚度比,探究了不同河谷地形下斜拉桥各墩/塔位置处的阻尼器合理屈服力.当边跨所处河谷边坡较陡峭时,宜在各墩/塔位置处均设置阻尼器,可以较好地控制辅助墩的墩-梁相对位移,并对各墩/塔进行有效减震,而当边跨所处河谷边坡较平缓时,可仅在主塔和过渡墩位置处设置阻尼器,能达到与各墩/塔位置处均设置阻尼器时相似的减震效果.Abstract: The reasonable transverse isolation system of typical long-span single-tower cable-stayed bridges with hybrid girders for mountainous areas was investigated.Based on the Jinsha River Bridge,the structural significant asymmetry,dynamic characteristics and seismic responses were analyzed.A method using influence matrix for calculating the reasonable damper parameters of the isolation system was proposed,and its convergence and the influencing factors were discussed by taking triangular steel dampers as an example.The results show an obvious correlation between the reasonable damper yield forces of the transverse isolation system and the corresponding bearing shear forces of the transverse fixed system,and proper initial yield forces and influence matrix could significantly improve the efficiency and stability of the iteration process.The effects of the local terrain on the reasonable yield forces of the dampers at different positions of the cable-stayed bridge were further analyzed based on the relative lateral stiffness ratio of the auxiliary piers to the transitional pier.In the case of the side span over a steep slope,it is recommended dampers be installed at all tower and pier locations,so that the relative displacements between the auxiliary piers and the girder and the seismic responses of the tower and piers could be well controlled; whereas in the case of a gentle slope,dampers could be set only at the tower and transitional pier locations,where a similar damping effect as the case of the dampers set at all tower and pier locations could be achieved.