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预测地震荷载下钢筋混凝土柱的力学性能,对评估震后混凝土结构的安全性和震害损失具有重要意义。由于混凝土材料在受力过程中的复杂性,目前对钢筋混凝土结构力学性能的模拟主要依靠数值方法。已有的数值模拟方法大都基于有限元法,将混凝土视为连续体,通过人为定义参数来指定混凝土的滞回本构,因此存在一定的主观性与局限性。该文结合扩展有限元法与断裂准则,直接模拟混凝土裂缝的开展与闭合,并考虑钢筋和混凝土的粘结滑移作用,通过数值计算,直接再现了钢筋混凝土结构在低周反复荷载下的力学行为。模拟方法得到了试验的验证,与结果吻合较好。该文进一步分析了钢筋混凝土柱的滞回行为中混凝土、钢筋的各自作用和相互抵消行为,从细观的角度,在机理上揭示了捏拢效应出现的三个主要原因。
Prediction of the mechanical properties of reinforced concrete columns under seismic load is of great significance for assessing the safety of post-earthquake concrete structures and the loss of seismic damage. Due to the complexity of the concrete material in the process of stressing, the current simulation of the mechanical properties of reinforced concrete structures relies mainly on numerical methods. The existing numerical methods are mostly based on the finite element method. The concrete is regarded as continuum, and the hysteretic constitutive equation of concrete is defined by the human-defined parameters. Therefore, there are some subjectivity and limitations. In this paper, the finite element method and fracture criterion are extended to directly simulate the initiation and closure of concrete cracks. Considering the bond-slip between reinforced concrete and concrete, the mechanical behavior of reinforced concrete structures under low cyclic loading is directly reproduced behavior. The simulation method has been verified by experiments, which is in good agreement with the results. This paper further analyzes the respective roles and mutual cancellations of concrete and rebar in the hysteretic behavior of reinforced concrete columns. From the perspective of microscopic view, three main causes of pinch-in effect are revealed in mechanism.