不同尺寸混凝土楔入劈拉试件双K断裂韧度试验研究与理论分析

为了研究不同尺寸的混凝土结构的断裂性能,设计了5组共20个不同截面高度的楔入劈拉试件进行混凝土断裂试验.改进了试验加载装置以抵消竖向力的作用,简化了分析计算.在双K断裂理论的基础上,采用应力强度因子叠加原理对不同截面高度的楔入劈拉试件的有效裂缝长度和双K断裂韧度进行了计算.试验结果表明:在200~700 mm设计的截面高度范围内,试件起裂荷载、失稳荷载及有效裂缝长度均随截面高度的增大而呈线性增大;起裂断裂韧度基本不受试件高度变化的影响;失稳断裂韧度在试件截面高度低于500 mm时表现出一定的尺寸效应,随试件高度增大而逐渐增大,当试件截面高度大于500 mm时其值趋于稳定,可认为是一个常数.

Experimental Research and Theoretical Analysis on Double-K Fracture Toughness of Different Size Wedge Splitting Tensile Specimen

To study the fracture performance of concrete structure of different size,5 groups including 20 wedge splitting tensile specimens with series of different section height were designed. The loading device was improved to simplify the analysis of vertical force.Based on double-K fracture theory,critical effective crack length and the double-K fracture parameters were calculated by using superposition principle of the stress intensity factor. The results show that the cracking load,the unstable load and the critical effective crack length increase linearly along with the increase of the cross section height which is from 200 mm to 700 mm; the crack fracture toughness is not affected by specimen height change; the unstable fracture toughness shows some size effect when the cross section height is less than 500 mm,and it increases with the grow of specimen height; when the height is greater than 500 mm,it can be considered as a constant.