DUCTILITY OF STEEL SHORT CYLINDERS IN COMPRESSION AND BENDING

During the Hyogoken-Nanbu earthquake near Kobe, Japan, on January 17, 1995, damage occurred not only in steel box-section bridge piers but a lso in pipe-section piers. The pipe-section piers are usually designed with relatively large radius-thickness ratios, which make them suscep tible to damage by local buckling during a severe earthquake event. To evaluate the damage of such columns, the ductility capacity of steel short cylinders is needed. For this purpose, an elastoplastic large de formation analysis of pipe-section stub-columns is carried out, In the analysis, a type of four-node doubly curved shell element is employed . Both the initial geometrical deflection and the residual stresses ar e taken into consideration. An elastoplastic strain hardening model is adopted to consider the material nonlinearity, Numerical results are then compared with previous test results and analytical results. In ad dition, a parametric study is conducted to investigate the effects of various parameters such as the length-diameter ratio, radius-thickness ratio, and axial load on the ultimate strength and ductility of the c ylinders. Finally, design formulas for the ultimate strength and ducti lity of the cylinders in compression and in combined compression and b ending are proposed.