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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。
According to the uniaxially-incised concrete axial tension member, an analytical model for calculating the ultimate bearing capacity is proposed based on the virtual fracture model, and the relationship between the tensile stress at the virtual crack tip and the tensile strength of the concrete core is established . The results show that the ratio of the two increases linearly with the increase of initial ratio, but is not sensitive to the change of concrete strength. The reason for this is that the axial tensile strength of the concrete obtained is the average of the cross-sectional stresses because the initial defects exist in all the concrete specimens, resulting in a significant stress gradient in the cross-section. The tensile stress at the virtual crack tip is, Maximum stress. Obviously, the longer the initial defect of the axis tension member, the larger the stress gradient of the cross section, the greater the ratio of the tensile stress to the average stress of the virtual crack tip. Normally, the tensile stress at the tip of the virtual fracture is about 1.22 times the tensile strength of the concrete core, which is approximately equal to the flexural strength of the concrete.