钢纤维混凝土带裂状态下抗弯承载力的计算方法

Calculation Method of Bending Load of SFRC in the Crack State

在混凝土中加入钢纤维,可使开裂后的混凝土仍能在开裂面传递拉应力,但钢纤维所传递的拉应力随裂缝宽度的增加而发生变化。因此以前认为钢纤维混凝土抗拉强度与裂缝宽度无关的设计方法,并未反映钢纤维混凝土的真实受力特性。本文通过四点弯曲试验,得到荷载与裂缝张开位移的关系。然后用受力平衡的方法,反算出钢纤维混凝土开裂后拉应力与裂缝宽度的关系,即拉伸软化曲线。通过分析发现,典型的钢纤维混凝土拉伸软化曲线,可以用其四个关键点的直线段描述。并根据实验数据,给出各段直线的确定方法。最后根据裂缝宽度和拉伸软化曲线,可以确定在指定裂缝宽度下,钢纤维混凝土的抗弯承载力。

With steel fibers added,the cracked concrete can still transfer the tensile force over the cracks.But the tensile stress transferred by steel fibers changes with the crack width.Thus the existing design method which considers no relationships between the tensile strength of the steel fiber reinforced concrete(SFRC) and the crack width does not reflect the actual force-bearing characteristics of the SFRC.The authors investigated the relationship between load and crack width by four points bending tests.Then the force equilibrium was used to calculate the relationships between the tensile stress and crack width,which was presented in form of the tensile strain softening curve.According the analysis,it was discovered that the typical curve can be described with straight line segments defined by four key points.And the authors proposed the method to determine the line segments based on experiment data.Finally,the bending load under the appointed crack width can be determined with known tensile strain softening curve.