用半圆形单边切口梁测定双K断裂参数

发布时间：2018-03-30 10:37

本文选题：半圆形单边切口梁　切入点：双K断裂参数　出处：《浙江大学》2015年硕士论文

【摘要】：混凝土结构受荷破坏前,裂缝扩展要经历三个阶段：裂缝起裂；裂缝稳定扩展和失稳破坏。双K断裂模型采用起裂韧度Klcm和失稳韧度K1cun,很好地描述了混凝土材料中裂缝扩展的这三个重要阶段。起裂韧度定义为起裂荷载时刻对应的初始裂缝尖端应力强度因子值,失稳韧度定义为最大荷载时刻临界裂缝尖端的应力强度因子值。本文采用半圆形单边切口梁测定了混凝土的双K断裂参数。分别采用三种不同直径(200,400和500 mm)的半圆形单边切口梁和四种不同强度(C2,C3,C4和C5)的混凝土进行断裂试验,研究试件尺寸及混凝土强度对双K断裂参数的影响。试验结果表明,采用半圆形单边切口梁测定的起裂韧度值和失稳韧度值均具有尺寸效应；此外,混凝土双K断裂参数还受混凝土强度的影响。随着试件尺寸增大,临界等效裂缝长度ac,临界裂缝口张开位移CMODc和失稳韧度均增大；而起裂韧度随试件尺寸的增大而减小。
[Abstract]:Before the concrete structure is damaged by load, the crack propagation has to go through three stages: crack initiation; The dual K fracture model uses the initial fracture toughness (Klcm) and the instability toughness (K _ 1 cununi) to describe the three important stages of crack propagation in concrete. The initial fracture toughness is defined as the initial crack loading moment. Stress intensity factor at the tip of the initial crack, The instability toughness is defined as the stress intensity factor value at the critical crack tip at the maximum load moment. In this paper, the double K fracture parameters of concrete are measured by using a semicircular one-sided notch beam with three different diameters of 200400 and 500mm, respectively. Fracture tests were carried out on circular unilateral notched beams and four kinds of concrete with different strength (C _ 2C _ 3C _ 3C _ 4 and C _ 5). The effects of specimen size and concrete strength on double K fracture parameters are studied. The experimental results show that both the initial fracture toughness and the instability toughness measured by the semicircular one-sided notch beam have a size effect. With the increase of specimen size, critical equivalent crack length ac. critical crack opening displacement CMODc and instability toughness increase, while initial fracture toughness decreases with the increase of specimen size.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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