Reinforcement Detailing for Local Cracking

当梁受到剪力、温度变化、板和墙的干缩或锚拔出时，在轻筋区占优势的混凝土裂缝倾向于不稳定地逐步发展。目前还没有建立预测这种裂纹扩展的计算方法，因此，理论上还不足以对钢筋进行详细的描述。利用线性断裂力学的应力强度因子来确定裂纹扩展的准则，并使用有限元分析。该方法被认为是合理的情况下，能够模拟裂纹的传播：受剪梁的对角拉伸开裂，锚拔出时开裂，钢筋在一定程度上抑制了裂缝的张开，对于所研究的每种行为，没有建立扩展裂纹的因素。正因为如此，在预测外部载荷扩展裂纹的各个阶段，直到结构破坏的准确性是不令人满意的。该方法有助于预测裂纹发展的分布和路径的情况下研究。因此，该方法被认为是有益的，详细的钢筋。

A crack in concrete dominant in lightly reinforced area tends to develop unstably and progressively in cases of beams subjected to shear, temperature change and drying shrinkage of slabs and walls, or anchor pull-out. Methods are not established for computation to predict propagation of such cracks, and consequently, theory is insufficient for reinforcement detailing.A method for computational simulations were developed for application to various behaviors using an assumption that a criteria for crack propagation is determined by stress intensity factors of linear fracture mechanics, and using finite element analysis.The method was found to be reasonably capable of simulating propagations of cracks in cases of : diagonal tension cracking in beams subjected to shear, cracking in anchor pull-out, and discrete cracking in slabs due to shrinkage where reinforcement restrained crack opening to a certain degree.Characteristic values for the stress intensity factors for propagating cracks are not established for each behaviors studied. Because of that, accuracies are not satisfactory in predicting external loads to propagate cracks at various stages up to strubtural failure. The method was found helpful for predicting distribution and paths of crack developments for the cases studied. Thus the method was deemed helpful for detailing reinforcement.