DUCTILITY EVALUATION OF STEEL BRIDGE PIERS WITH PIPE SECTIONS

The present paper is concerned with ductility evaluation of steel pipe -section bridge piers under cyclic loading. For this purpose, an elast oplastic large deformation analysis is carried out to obtain cyclic be havior of the columns. In the analysis, a modified two-surface plastic ity model developed at Nagoya University is employed to account for ma terial nonlinearity. The developed finite-element formulation takes in to account such important cyclic characteristics of structural steel a s the decrease and disappearance of the yield plateau, reduction of th e elastic range, and cyclic strain hardening as well as the spread of plasticity across the section. Comparisons between the analytical and experimental results show that the modified two-surface model gives cl oser prediction of the inelastic cyclic behavior of steel structures t han isotropic and kinematic models. A parametric study is then conduct ed to investigate the effects of radius-thickness ratio, slenderness r atio, magnitude of axial load, and number of loading cycles on the str ength and ductility of the columns. Finally, empirical formulas of the strength and ductility are proposed for steel bridge piers with pipe sections.