基于裂纹系的砼轴拉构件亚临界扩展研究  

A crack-system model for subcritical crack propagation in concrete members under axial tension

作　　者：郑涛 王桂尧[1] 张永杰[1] ZHENG Tao;WANG Guiyao;ZHANG Yongjie(School of Civil Engineering,Changsha University of Science&Technology,410114 Changsha,China)

机构地区：[1]长沙理工大学土木工程学院,长沙410114

出　　处：《应用力学学报》2024年第6期1317-1326,共10页Chinese Journal of Applied Mechanics

基　　金：国家自然科学基金资助项目(No.51878071);湖南省研究生科研创新资助项目(No.CX20210768)。

摘　　要：普通混凝土构件存在多裂纹的特点,现有的单裂纹模型仅反映了构件的抗裂能力,而没有反映构件内部在极限荷载之前既已发生的有害的裂纹发展情况。针对这一问题,提出采用裂纹系模型研究混凝土构件的亚临界扩展过程。为简化,选取轴拉构件为研究对象,以缝端微裂纹区模型为基础建立了楔形的单裂纹模型,并以几何分布参数——裂纹平均间距、裂纹初始长度及其数量百分比为框架建立了由单裂纹模型串式排列而成的裂纹系模型。采用该模型模拟了轴拉构件的受拉试验和断裂试验,结果表明选取合适的参数后模型能够准确反映混凝土宏观断裂过程和微观裂纹扩展过程,并且对于含预制裂缝试件,裂纹总数为实际数量的裂纹系模型结果与现有单裂纹模型结果吻合。采用该模型的分析表明,混凝土亚临界扩展过程源于混凝土初始裂纹系由长到短逐级开展;其真实起裂点远早于通常试验观测到的起裂点,其失稳点——失稳韧度可以通过减小混凝土初始裂纹系最小长度提高。In view of the multiple-crack characteristics of ordinary concrete members,the current theory based on the single crack model only reflects the ultimate crack resistance of the member,but does not reflect the harmful crack development inside the member before the ultimate load.A crack-system model was proposed to study the subcritical crack propagation process.For simplicity,the axial tension member was selected as the research object.First,a wedge-shaped model of single crack was established based on the micro-crack zone model of crack tip.Then,a crack-system model consisting of single crack arranged in string was established based on the geometric distribution parameters:average crack spacing,initial crack length and its number percentage.The results of simulating tensile test and fracture test of axial tension members show that the crack-system model can accurately reflect the macro fracture process and micro crack growth with appropriate parameters.For the specimen with prefabricated cracks,the results of the crack system model with the total number of cracks being the actual number are consistent with the results of the existing single-crack model.The further analysis using this model indicates that the subcritical crack propagation of concrete should be due to the progressive development of initial cracks in sequence from long to short;and the real crack initiation point is much earlier than that observed by normal tests,and the instability toughness can be improved by reducing the minimum length of the initial cracks.

关 键 词：断裂 裂纹系模型 统计学参数 亚临界扩展 混凝土断裂 试验模拟 

分 类 号：TU37[建筑科学—结构工程]