Response of steel bridge piers subjeceted to strong ground motions in the arbitrary horizontal direction and their seismic design concept

2000年开发了轴力和双向弯曲作用下钢空心构件的强度和延性数据库，关注构件的局部屈曲行为和细长参数。并对矩形、圆形等截面形状进行了评价。特别地，利用京都大学提供的三维载荷测试来获得这种强度和延展性。基于试验结果以及通用有限元软件ABAQUS的分析结果，提出了定义强度和延性的等效标量参数，即在双轴向受弯状态下各构件在恒定轴力作用下的强度和延性的平方和的平方根。利用该参数，可以同等地评价所有不同位移路径对荷载-挠度曲线包络线的影响，并发现复杂双向荷载作用下的强度衰减显著。为了验证所提出的强度和延性评价公式的适用性，进行了反应分析和拟动力加载试验。人工地面运动也被归一化，以评估反应的变化。结果表明，三维地震动的性质对桥梁结构的反应有很大影响，因此，考虑结构的方向和垂直方向等结构不对称性，对三维地震动的影响进行定量分析是一项迫切的任务。

Carried out in 2000 was the development of the data-base for the strength and the ductility of steel hollow members subjected to axial force and bi-directional bending, paying attention to local buckling behavior in conjunction with slenderness parameters of members. Assessment on the cross sectional shape such as rectangular and circular was also made. In particular, the three dimensional loading testing available at Kyoto Univeristy was utilized to obtain such strength and ductility. Based on the experimental results as well as the analytical results by the general-purpose finite element code ABAQUS, the equivalent scalar parameter to define the strength and ductility, namely the square root of summation of square of each component in biaxial bending state under constant axial force. By using this parameter, effect of all the different displacement paths on the envelop curve of load-deflection curves up to the maximum strength point are equally evaluated, and the significant strength degradation for complex biaxial loading was found.In 2001, following the static loadings test on steel bridge piers, the response analysis and pseudo-dynamic loading tests were carried out in order to verify the applicability of strength and ductility evalution formula proposed previously. Artifitial ground motions were also unilized to assess the variation of the response. It is concluded that the nature of three dimentional ground motions affects the response of bridges, resulting the urgent task to quantify such effect by taking into consideration the structural unsyfnmetry such as the directions of bridges and its perpendicular direction.