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

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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