Spatial hysteretic model and elasto-plastic stiffness of steel columns

By defining yielding function, F, and introducing a so called deformation parameter, R, a simple hysteretic model is proposed between F and R to link 3-dimensional forces acting on a section of a steel column and yielding degree of the section. Based on the hysteretic model proposed and plastic flow laws, the spatial elasto-plastic stiffness equation of steel columns is established. The effectiveness and reliability of the hysteretic model and stiffness equation are verified by experiments through applying the theory to predicting the behavior of 6 specimens of box and H-shaped steel columns subjected to constant vertical loads and repeated and reversed bi-directional horizontal loads. The achievements made in this paper provide the key to problems in the analysis of spatial elasto-plastic responses of steel buildings subjected to earthquakes. (C) 1999 Elsevier Science Ltd. All rights reserved.