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为了研究冻融环境下钢筋混凝土框架节点的抗震性能,对6个经受不同冻融循环次数作用后的钢筋混凝土框架节点进行低周反复加载试验,分析框架节点的滞回曲线特性。基于试验结果,得到了简化三折线型骨架曲线模型,并给出了相应的确定方法。采用回归分析方法,得到考虑冻融损伤的钢筋混凝土框架节点的极限功比系数I数学表达式,进而确定基于循环耗能的循环退化指数,通过对构件在反复荷载作用下的屈服荷载、硬化刚度、卸载刚度以及承载力等各项力学性能的退化机理进行了描述,进一步建立适应于冻融损伤的钢筋混凝土框架节点的恢复力模型,并给出了具体的滞回曲线规则。研究表明:冻融作用使得节点梁纵筋粘结性能劣化明显,累积耗能随着冻融循环次数的增加而降低;通过考虑刚度、强度的循环退化规律能更好的反应冻融节点“捏缩”效应,更与实际吻合;建议的恢复力模型与试验结果想接近,可为该类结构的弹塑性时程分析提供理论参考。
In order to study the seismic behavior of reinforced concrete frame joints in freezing-thawing environment, six reinforced concrete frame joints subjected to different freeze-thaw cycles were subjected to repeated low-cycle loading tests to analyze the hysteresis curve characteristics of frame joints. Based on the experimental results, a simplified three-fold linear skeleton curve model is obtained, and the corresponding determination method is given. Using regression analysis method, the limit work ratio coefficient I mathematical expression of the reinforced concrete frame joints considering freezing and thawing damage was obtained, and then the cyclic degradation index based on cyclic energy consumption was determined. Through the analysis of yield load, , Unloading stiffness and bearing capacity of various mechanical properties of the degradation mechanism is described to further establish the resilience model of the joints of the reinforced concrete frame to adapt to freeze-thaw damage, and gives the specific rules of hysteresis curve. The results show that the freeze-thaw effect makes the longitudinal beam of the beam have a significantly deteriorated bond performance, and the cumulative energy dissipation decreases with the increase of the number of freeze-thaw cycles. By considering the cyclic degradation of stiffness and strength, The result shows that the proposed model of restoring force is close to the experimental one and can provide a theoretical reference for the elasto-plastic time history analysis of such structures.