考虑纵筋屈曲及疲劳损伤的钢筋混凝土柱抗震性能试验研究与非线性分析

基于柔度法的纤维模型能更高效地计算钢筋混凝土柱的材料强非线性受力特征，但不考虑纵筋屈曲、疲劳损伤的钢筋本构模型仍将明显降低其受力后期的数值模拟精度。以8根钢筋混凝土柱抗震性能试验结果为基础，在OpenSees平台上采用可以考虑纵筋屈曲、疲劳损伤的钢筋本构模型以及柔度法纤维模型，对柱的滞回性能进行分析。分析结果表明，与小轴压比柱相比，纵筋屈曲对高轴压比柱峰值荷载之后的水平承载力退化影响更明显；对纵筋长径比小于3.0的柱，纵筋屈曲对非线性分析结果的影响可基本忽略；纵筋长径比为5.00~8.75且柱轴压比较小时，纵筋屈曲对分析结果有一定影响，但考虑疲劳损伤的计算结果能更好模拟柱软化段的水平承载力退化特征；柱轴压比较大且纵筋长径比为6.25~7.00时，考虑纵筋屈曲、疲劳损伤均会明显减小承载力退化的计算误差。同时考虑纵筋屈曲及疲劳损伤的分析结果能更好地反映柱的承载力退化特征。

Experiments and nonlinear analysis on seismic behavior of RC columns considering buckling and fatigue damage of reinforcing steel bar

Flexibility method based fiber model could calculate strong material nonlinear hysteresis responses of reinforced concrete columns more efficiently, but the accuracy of numerical simulation for the capacity of column at later soften phase after peak will be obviously decreased if buckling and fatigue damage of longitudinal reinforcing bar were not considered in the constitutive model. Based on the seismic behavior experimental results of eight reinforced concrete columns, the hysteresis nonlinear responses of the columns were simulated by adopting constitutive model including buckling and fatigue damage of bar and flexibility method based fiber model within the OpenSees platform. The results show that, with respect to the column of small axial force ratio, namely the ratio of axial force to column sectional area and compressive strength of concrete, the influence of bar buckling on the strength degradation after peak capacity of the high axial force ratio column is obviously greater. For the column with slenderness ratio of longitudinal bar less than 3.0, the influence of bar buckling on the nonlinear analysis results can be basically ignored. In the case of the column with slenderness ratio being 5.00 to 8.75 and axial force ratio being small, buckling have certain effect on the analysis result, but better analysis results of strength degradation characteristics of column at softening phase can be obtained if fatigue damage is considered. For the column with axial force ratio being high and slenderness ratio being 6.25 to 7.00, both of buckling and fatigue damages will evidently decrease the analysis error of strength degradation. Considering buckling and fatigue damages simultaneously is found to be beneficial to obtain better simulation results of strength degradation characteristics of column.