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

本研究的目的是建立薄壁钢桥墩在三维地震作用下的滞回模型。首先，开发了三维加载和测量系统及其控制程序，进行了三维拟动力实验。其次，利用三维试验系统，对圆形和矩形钢桥墩的滞回特性进行了双向循环加载试验研究。第三，利用这些结果，检验了用三面本构模型进行非线性有限元壳分析的准确性。结果表明，当钢墩承受较大的塑性变形时，分析的准确性略差。为了提高计算精度，本文对原三面本构模型进行了改进，引入了有效等效塑性应变作为内变量的概念，而不是传统的等效塑性应变。第四，进行了广泛的非线性有限元分析，以评估结构参数对双向循环荷载作用下钢墩滞回性能的影响。这些结果被用于推导圆形和矩形钢墩在一个主方向上的强度和延性的经验公式。最后，在这些经验公式的基础上，提出了单向滞后模型。该模型隐含地考虑了双向循环荷载的影响，可直接适用于用单向地震波检验桥墩安全性的对流抗震设计。此外，还提出了多弹簧模型。该模型由集中质量和位于桥墩底部的刚性杆和多个弹簧组成。各弹簧的本构关系由钢墩的单向滞回特性决定。数值结果表明，在实际应用中，多重弹簧模型是一种可接受的替代有限元壳分析方法。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