混凝土紧凑拉伸试件断裂韧度计算模型

A MODEL FOR FRACTURE TOUGHNESS PREDICTION IN COMPACT TENSION SPECIMEN OF CONCRETE

根据混凝土的软化特性,通过紧凑拉伸试件失稳断裂破坏临界状态的力学分析建立了混凝土断裂韧度的解析计算模型。以混凝土的弹性模量和有效裂缝长度尖端的应力为两个基本参数,可推导出紧凑拉伸试件的极限承载力以及临界有效裂缝长度,进而求得混凝土的断裂韧度。通过计算结果与实验数据的比较发现,此模型能较为准确地预测紧凑拉伸试件的承载力以及裂缝张口位移,而且理论上简单实用。在此基础上研究了断裂韧度的尺寸效应,发现在实验室常用尺寸范围内,根据该文所建模型计算得到的断裂韧度不具有尺寸效应,可作为材料常数用于裂缝扩展判定。

A practical model to estimate fracture toughness of concrete was developed by utilizing the equilibrium of forces at the cracked section in unstable fracture state of compact tension specimen, where the softening feature of concrete was taken into account. With Young＇s modulus and the stress at the effective crack tip as two only prerequisites, the model can predict the maximum load and its corresponding effective crack length, and in turn the fracture toughness of concrete specimen under compact tension. Compared with test data available, a favorable agreement was observed for the maximum load and its corresponding crack mouth opening displacement. Based on the model presented, which is simple in theory and accurate in practice, size effect on fracture toughness was investigated. The results indicate that the fracture toughness from the proposed model exhibits little size effect for specimen of normal size in laboratory, and could be regarded as material constant, which could be used to determine whether a crack will propagate.