PIVOT HYSTERESIS MODEL FOR REINFORCED-CONCRETE MEMBERS

For nonlinear dynamic seismic analysis of bridge structures to be prac tical, only the dominant nonlinear characteristics of the structures s hould be included. Based on capacity design principles, the current se ismic bridge design philosophy is generally to force all member nonlin earities into the ends of ductile columns. Therefore, nonlinear charac teristics of the columns must be adequately defined. In this paper, a hysteresis model is presented which accurately captures the nonlinear behavior of reinforced concrete members in terms of a force-displaceme nt, or moment-rotation, response. What makes this model attractive, wh en compared to other hysteresis models, is that unsymmetric sections ( non-symmetric cross-section geometry and/or tension reinforcement amou nts in the two loading directions), a cyclic axial load, and strength degradation may be included. The model is based on a few simple rules. Results based on the proposed hysteresis model show close agreement w ith various experiments on reinforced concrete members.