In　order　to　effectively　simulate　the　nonlinear　hysteresis　behavior　of　reinforced　concrete　(RC)　bridge　piers　under　strong　earthquake　excitation,　an　improved　nonlinear　hysteresis　model　for　RC　bridge　piers　was　developed　and　its　controlling　parameters　were　determined　considering　stiffness　and　strength　degradation　and　pinching　effect　based　on　classical　Bouc-Wen　model.　The　improved　model　can　be　carried　out　to　predict　the　nonlinear　hysteresis　behavior　of　RC　bridge　piers　under　various　failure　modes　using　MATLAB/Simulink　program.　Cyclic　tests　of　different　failure　mode　bridge　column　specimens　were　performed　under　constant　axial　load　with　lateral　bending.　The　results　did　show　that　force-displacement　relationship　curves　of　bridge　column　specimens　derived　from　theoretical　analysis　agree　well　with　the　experimental　results.　The　nonlinear　hysteresis　behavior　of　bridge　column　specimen　was　simulated　under　2008　Wenchuan　earthquake　excitation　and　its　failure　modes　were　identical　with　the　real　earthquake　damage　of　bridge　column.　The　improved　analytical　models　in　the　paper　were　applied　to　accurately　predicting　the　nonlinear　hysteresis　behavior　of　RC　bridge　columns　with　strength　and　stiffness　degradations　and　the　pinching　effect　subjected　to　strong　earthquake　motion.　Unscented　Kalman　filter　(UKF)　was　applied　to　estimate　the　parameters　of　Bouc-Wen　model　in　this　paper,　the　simulation　results　and　error　analysis　show　that　the　method　can　accurately　estimate　the　parameters　of　improved　Bouc-Wen　model.　©,　2015,　Zhendong　Gongcheng　Xuebao/Journal　of　Vibration　Engineering.　All　right　reserved.