预裂纹混凝土拉压疲劳荷载下裂纹扩展速率

资料大小：950KB
资料类型：.PDF
资料等级：
发布时间：2021-09-04

资料介绍

预裂纹混凝土拉压疲劳荷载下裂纹扩展速率
沈健，冯仲仁，王雄江
(1．江西科技师范大学建筑工程学院，江西南昌330013；
2．武汉理工大学土木工程与建筑学院，湖北武汉430070)
摘要：为研究C50混凝土预裂纹在拉压循环荷栽下的扩展速率，进行了应力比为一1，应力幅值为
0．2O～1．30 MPa的拉压疲劳试验．针对混凝土在拉压疲劳荷载下裂纹扩展时其长度不易确定的问
题，提出潜行等效裂纹长度假说对试验结果进行分析．结果表明：混凝土裂纹第1阶段起始扩展区
和第2阶段稳定扩展区比较明显，第3阶段加速扩展区不明显，在稳定扩展区后期，裂纹扩展曲线
的斜率并不像金属那样快速增加，而是增幅趋缓，在稳定扩展阶段后期无征兆突然破坏，与混凝土
脆性断裂的特性相一致．利用最小二乘法拟合得到裂纹扩展速率Pairs公式中的参数C，，在考虑
50 ，90 ，99 的存活率时，C可在0．31～0．45，0．76～0．99，1．22～1．98中取值，m取值范围对
存活率大小的敏感性较低，可在3．0～4．8之间取值．
关键词：裂纹扩展速率；疲劳试验；疲劳荷载；混凝土
中图分类号：TU528．01 文献标志码：A doi：10．3969／i．issn．1007—9629．2014．03．028
Crack Growth Rate of Concrete with Pre—cracks in
Tension—Compression Cyclic Fatigue Load
SHEN Jian ， FENG Zhongren。。WANG Xiongjiang
(1．School of Architecture，Jiangxi Science and Technology Normal University，Nanchang 330013，China：
2．School of Civil Engineering and Architecture，W uhan University of Technology，W uhan 430070，China)
Abstract：A tension—com pression cycle fatigue test was perform ed in order to study the crack growth rate of
C50 concrete with pre—cracks in cyclic loading．The stress ratio was 一1 and the amplitude was 0．20 —
1．3O MPa．The concrete crack length is difficult to determine when the crack is propagating in tension—
compression fatigue load，SO the hypothesis of hidden equivalent crack length is put forward to analyze the
experimental data． Compared with the 3-stage diagram of com mon m etal crack propagation， the initial
propagation at the first stage and the second stage of stable propagation are quite notable but at the third
stage of accelerated expansion is not notable．At the late stage of stable propagation，the slope of fatigue
crack propagation curve does not increase as fast as that for metal materials but decelerates obviously and
the concrete fails suddenly without indication．It is consistent with the brittle fracture of concrete． The im—
portant param eters of Pairs form ula，C and ，are fit by the least squares． W hen the survival rate is 50 ，
90 or 99 ，C value range is 0．3l一0．45，0．76—0．99，1．22—1．98 and m va1ue range with low surviva1
rate sensitivity is 3．0—4．8．
Key words：crack growth rate；fatigue testing；fatigue load；concrete
裂纹是混凝土结构无法回避的问题．在施工养护及使用阶段，会因不同原因出现或多或少的各类