高温后钢筋再生混凝土偏压柱受力性能试验研究及承载力计算

Experimental study on mechanical behavior and bearing capacity calculation of reinforced recycled aggregate concrete eccentric compression column after exposure to high temperatures

为研究高温后钢筋再生混凝土柱的偏压性能,以历经温度、再生粗骨料取代率和荷载偏心率为变化参数,设计9个钢筋混凝土柱试件(包括8个高温后试件和1个常温试件)进行静力单调加载试验,观察其表观变化和破坏形态,获取了荷载-变形曲线及截面应变,分析各变化参数对混凝土极限压应变、峰值荷载、抗弯刚度和位移延性系数的影响规律。采用ABAQUS有限元分析软件对截面温度场进行模拟,并基于模拟和试验结果对钢筋再生混凝土偏压柱的计算方法进行了研究。研究结果表明:随温度升高或偏心率增大,钢筋再生混凝土柱破坏形态表现为从大偏压向小偏压转变;混凝土极限压应变与历经温度、取代率以及偏心率呈正相关;峰值荷载和抗弯刚度随温度升高或偏心率增大而降低,在600℃时出现陡降,其中抗弯刚度衰减相对更快,而取代率影响相对较小;普通混凝土柱延性更好,而再生混凝土柱在600℃时延性最优,且偏心率越大延性越好;随截面深度增加,截面温度场呈指数函数递减,且取代率增大会加快衰减;最后,综合有限元模拟结果和试验结果提出了偏压柱承载力计算方法,计算结果与试验结果吻合较好。

In order to reveal the mechanical behavior of recycled aggregate concrete columns under eccentric loading after exposure to high temperatures, nine specimens(including eight specimens after exposure to high temperatures and one specimen at normal temperature) with different replacement ratios, high temperatures and eccentricities were test under monotonic load. The apparent changes and failure modes of specimens were observed, and then the load-deformation curves as well as the strain distributions were obtained, the effects of various parameters on peak load, ultimate compression strain, flexural rigidity and ductility were analyzed. Furthermore, the temperature field of specimens was simulated by ABAQUS. Based on the results of tests and ABAQUS, the calculation method of ultimate bearing capacity was discussed. The results show that with the increase of temperature or eccentricity, the failure modes of specimens change from large eccentric compression to small eccentric compression. The ultimate compression strain is positively correlated with replacement ratio, temperature and eccentricity. With the increase of temperature or eccentricity, the peak load and the flexural rigidity decrease, and a steep drop occurs at 600 ℃, at which the flexural rigidity declines relatively faster, while the influence of replacement ratio is relatively small. The ductility of ordinary concrete is better. The ductility of recycled concrete reaches the best at 600 ℃. The larger the eccentricity, the better the ductility. The temperature field decreases exponentially as the increase of section depth, and the increase of replacement ratio speeds up the decrease. Finally, based on the results of finite element simulation and experiment, a method for calculating the bearing capacity of eccentric compression column is proposed, and the results agree well with experimental results.