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

2000年开展了空心钢构件在轴力和双向弯曲作用下的强度和延性数据库的开发工作，考虑了构件的局部屈曲行为和构件的长细参数。并对矩形、圆形等截面形状进行了评定。特别是，京都大学的三维加载试验被用来获得这样的强度和延性。根据试验结果以及通用有限元程序ABAQUS的分析结果，提出了定义强度和延性的等效标量参数，即在恒定轴力作用下双向弯曲状态下各构件的平方和的平方根。利用该参数，同等评价了不同位移路径对最大强度点荷载-挠度曲线包络曲线的影响，发现在复杂的双向荷载作用下，强度有明显的退化。2001年，在钢桥墩静载试验的基础上，进行了响应分析和拟动载试验，以验证提出的强度和延性评价公式的适用性。人工地面运动也是单方面的，以评估反应的变化。结果表明，三维地震动的性质会影响桥梁的反应，因此考虑桥梁的方向及其垂直方向等结构不对称性来量化这种影响是当务之急。

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.