虚拟裂缝尖端拉应力大小的确定  

DETERMINATION OF THE TENSILE STRESS AT FICTITIOUS CRACK TIP

作　　者：杨树桐[1] 

机构地区：[1]中国海洋大学工程学院土木工程系,山东青岛266100

出　　处：《工程力学》2012年第11期170-174,共5页Engineering Mechanics

基　　金：国家自然科学基金项目(50908136;E080501)

摘　　要：针对单边切口的混凝土轴心受拉构件,基于虚拟裂缝模型提出一种计算极限承载力的解析模型,并在此基础上确立了虚拟裂缝尖端拉应力与混凝土轴心抗拉强度之间的关系。结果表明:二者的比值随初始缝高比的增大呈线性增加,但对混凝土强度等级的变化不敏感。其原因是由于所有的混凝土试件都存在初始缺陷,导致截面上存在明显的应力梯度,因而得到的混凝土轴心抗拉强度值是截面应力的平均值,而虚拟裂缝尖端拉应力为截面上的最大应力。很显然,轴心受拉构件的初始缺陷越长,截面的应力梯度越大,虚拟裂缝尖端拉应力与平均应力的比就越大。通常情况下,虚拟裂缝尖端的拉应力大小约为混凝土轴心抗拉强度值的1.22倍,约等于混凝土的抗折强度。An analytical model is presented to determine the peak load of single-edge notched concrete specimens subjected to uniaxial tensile loads, based on a fictitious crack model. Then the relationship between the tensile stress at the fictitious crack tip and the uniaxial tensile strength of concrete is established based on the proposed model. The results show that the ratio of the tensile stress at the fictitious crack tip to the uniaxial tensile strength of concrete increases with the increase of the initial crack length but is insensitive to the concrete strength It is mainly because that there are always apparent stress gradients in the cross-sections due to the inevitable initial cracks in concrete specimens, and hence the uniaxial tensile strength should be the mean value of the stresses in the cross-section. But the tensile stress at the fictitious crack tip is the maximum stress in the cross-section. Obviously, the stress gradient increases with the increase of the initial crack length. Consequently, the ratio of the tensile stress at the fictitious crack tip to the uniaxial tensile strength of concrete becomes larger. The tensile stress at the fictitious crack tip is generally approximately 1.22 times of the uniaxial tensile strength of concrete and around the value of the modulus of rupture.

关 键 词：混凝土 轴心受拉构件 解析模型 虚拟裂缝尖端拉应力 轴心抗拉强度 抗折强度 

分 类 号：O346.1[理学—固体力学] TU528[理学—力学]