3-dimentional pseudo-dynamic experiment on steel bridge piers and their hysteretic models

本研究的目的是建立一个薄壁钢桥墩在三维地震作用下的滞回模型。首先，开发了三维拟动力试验的加载系统和测量系统，并编制了相应的控制程序。其次，利用三维试验系统，对圆形和矩形钢桥墩进行了双向低周反复加载试验，研究了圆形和矩形钢桥墩的滞回性能。第三，利用这些结果，三面本构模型的非线性有限元分析的准确性进行了检查。据观察，当钢桥墩受到大的塑性变形时，分析的准确性变得有点差。为了提高模型的精度，对作者提出的三面本构模型进行了修正，引入了有效等效塑性应变的概念，代替了传统的等效塑性应变作为内变量。第四，广义非线性有限元 关于我们 采用M分析方法研究了结构参数对双向循环荷载作用下钢桥墩滞回性能的影响。这些结果被用来推导经验公式的强度和延性的圆形和矩形钢桥墩在一个主方向。最后，根据这些经验公式，提出了单向滞回模型。该模型隐式地考虑了双向循环荷载的影响，可直接应用于用单向地震波检验桥墩安全性的常规抗震设计。此外，提出了一种多弹簧模型。该模型由一个集中质量和一个刚性杆与多个弹簧位于桥墩基础。每个弹簧的本构关系由钢桥墩的单向滞回特性决定。数值结果证实，多弹簧模型是一个可接受的替代有限元壳分析的实际目的。少

The objective of the present research is to develop a hysteretic model of thin-walled steel bridge piers subjected to 3D earthquake excitations. Firstly, 3D loading and measuring systems along with the control programs were developed for a 3D pseudo-dynamic experiment. Secondly, by using the 3D experiment system, bi-directional cyclic loading experiments were conducted to investigate the hysteretic behaviors of circular and rectangular steel piers. Thirdly, utilizing these results, the accuracy of the nonlinear FEM shell analyses with the 3-surface constitutive model was examined. It was observed that the accuracy of the analysis gets a little worse when the steel piers are subjected to large plastic deformations. To improve the accuracy, the original 3-surface constitutive model developed by authors was modified by introducing a concept of effective equivalent plastic strain as an internal variable instead of the conventional equivalent plastic strain. Fourthly, extensive nonlinear FE … More M analyses were conducted to assess the effects of structural parameters on the hysteretic behaviors of steel piers under bi-directional cyclic loads. These results were used to derive empirical formulas for the strength and ductility of circular and rectangular steel piers in one principal direction. Lastly, a unidirectional hysteretic model was proposed on the basis of these empirical formulas. This model implicitly considers the effect of the bi-directional cyclic loads and can be directly applicable to the convectional seismic design where the safety of bridge piers is examined by unidirectional earthquake waves. In addition, a multiple spring model was proposed. This model consists of a concentrated mass and a rigid bar with multiple springs located at the pier base. The constitutive relation of each spring is determined by the unidirectional hysteretic behavior of steel piers. Numerical results confirmed that the multiple spring model is an acceptable alternative to the FEM shell analysis for practical purposes. Less