氯盐锈蚀钢框架柱抗震性能试验及恢复力模型研究

Experimental Study of Seismic Behaviors and Restoring Force Model Research of Corroded Steel Frame Columns Induced by Chloride Ions

为研究氯盐锈蚀钢框架柱抗震性能并建立其恢复力模型,利用人工气候环境法对48件不同厚度钢材和4榀钢框架柱试件进行加速锈蚀,进而对锈蚀钢材试件进行单轴拉伸试验,并对锈蚀钢框架柱试件进行低周往复加载试验.试验结果表明:随着锈蚀程度的加重,钢材的屈服强度、极限强度、延伸率和弹性模量等力学性能发生劣化,最大下降幅度分别为12.78%、12.78%、21.13%、13.28%;随着失重率的增大,钢框架柱承载、变形及耗能能力等抗震性能退化明显,其中,当失重率增大至8.02%时,峰值弯矩、极限转角、延性系数和累积耗能能力分别降低了17.34%、24.21%、12.32%和18.64%.基于修正I-K模型,结合拟静力试验结果,建立完好钢框架柱试件的弯矩-转角恢复力模型,并采用回归分析法,以失重率为参数,对钢框架柱骨架曲线各特征点弯矩、转角及延性系数进行拟合,得到考虑锈蚀影响的钢框架柱骨架曲线特征参数修正函数;在此基础上,通过循环退化指数表征基本强度退化、峰值后强度退化、卸载刚度退化等滞回规则,进而建立考虑氯盐锈蚀影响的钢框架柱弯矩-转角恢复力模型.通过与试验滞回曲线及峰值点、极限点累积耗能对比,两者吻合较好,验证该恢复力模型的有效性.研究成果可为受氯盐锈蚀影响的在役钢框架结构弹塑性地震反应分析及抗震性能评估提供依据.

To study the seismic behavior of corroded steel frame columns induced by chloride ions and establish their resilience model,48 specimens of steel with different thicknesses and four specimens of steel frame columns were accelerated to corrode by the artificial climate environment method.Further,uniaxial tensile tests were carried out on the corroded steel specimens,and low cyclic loading tests were carried out on the corroded steel frame columns.The test results showed that as the corrosion degree increased,the mechanical properties of steel such as yield strength,ultimate strength,elongation,and elastic modulus deteriorated,and the maximum reduction value was 12.78%,12.78%,21.13%,and 13.28%,respectively.With the increase of weight loss rate,the seismic performance of steel frame columns,e.g.,load-bearing capacity,deformation capacity,and energy dissipation capacity,degraded significantly.When the weight loss rate increased to 8.02%,peak bending moment,ultimate rotation angle,ductility coefficient,and cumulative energy dissipation capacity decreased by 17.34%,24.21%,12.32%,and 18.64%,respectively.Based on the modified I-K model and the quasistatic test results,the moment rotation restor-ing force model of the intact steel frame column was established.With the weight loss rate as the parameter,the bending moments,rotations,and ductility coefficients of each feature point of the steel frame column skeleton curve were fitted by the regression analysis method to obtain the feature parameter correction function of the corroded steel frame column skeleton curve.On this basis,the hysteretic rules such as basic strength degradation,post-peak strength degradation,and unloading stiffness degradation were characterized by cyclic degradation index.The mo-ment-rotation restoring force model of corroded steel frame columns was then established.The experimental hysteretic curve and cumulative energy consumption at the peak and limit points were in good agreement with each other,which verifies the effectiveness of the restoring force model.The research results of this study can provide a basis for the elastic-plastic seismic response analysis and the seismic performance evaluation of the existing steel frame struc-tures affected by chloride corrosion.