考虑徐变非线性的钢管混凝土柱徐变稳定承载力计算方法

Prediction equation for creep buckling capacity of concrete-filled steel tubular columns considering nonlinear creep

对高持荷荷载作用后钢管混凝土柱稳定性能进行了数值分析,同时结合初弯曲构件稳定理论和Perry公式,通过理论推导提出了钢管混凝土柱徐变后稳定承载力计算公式。为深入研究构件徐变稳定性能,将钢管混凝土非线性徐变模型以及考虑约束作用和材料非线性的应力-应变关系引入ABAQUS,建立了钢管混凝土柱有限元分析模型;在验证了有限元模型可靠性的基础上,通过参数分析研究了长细比、含钢率、长期荷载等级、混凝土强度以及钢材屈服强度对构件徐变稳定承载力的影响;并将理论推导所得构件徐变稳定承载力计算公式与有限元分析结果进行了对比。结果表明:时效作用对钢管混凝土柱稳定性能的影响不容忽视,可使构件稳定承载力降低15.5%;影响构件徐变稳定承载力的主要参数包括长细比、长期荷载等级、含钢率,其中混凝土强度及钢材屈服强度的影响较小;所提公式计算结果与有限元分析结果吻合良好,最大差值不超过10%,公式计算结果与有限元分析结果比值的均值为1.01,标准差为0.035,变异系数为3.4%。

Numerical analysis was carried out on the stability of concrete-filled steel tubular(CFST) columns subjected to high level of sustained load. Using the initial bending stability theory and the Perry formula, formula was proposed through theoretical derivation to predict the load carrying capacity of CFST columns after experiencing time effects. For the creep buckling analysis of CFST columns, the nonlinear creep model of CFST and the stress-strain relationship considering the confinement effects and material nonlinearity was introduced into ABAQUS, and the finite element analysis model of CFST columns was established and verified against available experimental data. A parametric analysis was conducted to study the influences of slenderness ratio, steel ratio, long-term load level, concrete strength and steel yield strength on the creep buckling behavior of the columns. The theoretically deduced formula was validated by comparing the predicted results with those of the finite element analysis. It is found that the influence of time effect on the stability of CFST columns can reduce the load carrying capacity of CFST columns by up to 15.5%, which cannot be neglected in the design. The main parameters influencing the creep buckling behavior of the CFST columns include the slenderness ratio, the long-term load level and the steel ratio;while the concrete strength and the steel yield strength have relatively little influence on the creep buckling behavior of CFST columns. The proposed formula was in good agreement with the finite element analysis results with the mean value of 1.01, the standard deviation of 0.035 and the variable coefficient of 3.4%;and with the maximum difference less than 10%.