Cyclic Large Displacement Analysis of Steel Tubular Bridge Piers under Combined Axial and Bidirectional Lateral Loading
Iraj H.P. Mamaghani, Fokruddin Ahmad, Basha Dorose

Abstract
This paper deals with the large displacement analysis of thin-walled steel tubular bridge piers subjected to cyclic bidirectional lateral loading in the presence of constant axial load. In comparison with the behavior of such piers under conventional cyclic unidirectional lateral loads, the deterioration in strength and ductility caused by severe cyclic lateral bidirectional loads is examined based on nonlinear finite-element analysis and test results. Pseudo dynamic bidirectional tests, available in the literature, are used to substantiate the accuracy of the finite-element analysis. The results confirm the importance of considering the behavior of steel tubular bridge piers under bidirectional lateral loading. The bidirectional tests and finite element analysis results showed that the behavior of steel tubular bridge piers under bidirectional lateral loading becomes complex and exhibits a circular trajectory once local buckling occurs. The local buckling bulge in the bidirectional loading case tends to develop monotonically due to this circular trajectory. As a result, the residual deformation becomes larger. The unidirectional loading test and analysis are likely to underestimate the damage and the residual displacements caused by an earthquake. It is concluded that the effects of bidirectional lateral loading should be considered in ductility evaluation and seismic design of steel tubular bridge piers.

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