混凝土断裂参数厚度尺寸效应的定量表征与机理分析

Quantitative characterization and mechanism analysis on thickness-dependent size effect of concrete fracture

该文主要研究混凝土断裂参数的厚度尺寸效应,所进行的断裂试验属于国际材料与结构试验室联合会(RILEM)TC265-TDK委员会为制定双K断裂参数国际通用规范开展的国际联合试验的一部分。通过5组(共计29根)不同厚度(100~300mm)普通混凝土梁的标准三点弯曲试验,测定了双K断裂韧度KiniIc和KunIc、断裂能GF、特征长度lch等相关断裂参数,并用归一化(无量纲化)方法定量表征了各断裂参数随试件厚度的变化规律。进一步地,基于国内现行《水工混凝土断裂试验规程》(DL/T 5332—2005)中的线弹性断裂韧度计算公式、Weibull尺寸效应理论以及混凝土多轴强度理论,分析了试验所呈现的厚度尺寸效应特征。试验结果和理论分析表明,混凝土各断裂参数均不存在明显的厚度尺寸效应,且各参数的结论可以互相印证。

In this work, an experimental study on the thickness-dependent size effect of concrete fracture parameters, as one of the experiments stipulated by RILEM TC265-TDK Technical Committee （testing methods of determining the double-K criterion for crack propagation in concrete）, is carried out. The double-K fracture toughness and the fracture energy of 29 beam specimens in 5 groups with the thicknesses varying from 100ram to 300ram is measured based on the three-point bending test. The relationship between the fracture parameters and the thickness of specimens is evaluated quantitatively. In addition, the thickness-dependent size effect of concrete fracture parameters is discussed based on the linear elastic formula of fracture toughness, the theory of Weibull size effect and the muhi-axial strength theory of concrete. Experimental results and theoretical analysis indicate that there exists no remarkable thickness-dependent size effect for the fracture parameters of concrete.