摘   要：根据弯曲和拉伸组合作用下的单根纤维的受力状态，提出了细观变位约束模型以求解承受轴拉的随机各向分布纤维增强混凝土的力学性能。将单根随机纤维的理论解在三维空间进行积分运算，有效描述了受拉纤维混凝土开裂后的受力过程，并给出了复合材料拉伸应力与裂纹张开位移、纤维倾斜角的函数关系，绘制的合成纤维混凝土曲线与试验结果有较好的一致性。

Abstract: According to the forced state of single randomly oriented fiber under the combined action of bending and stretching, using the meso-scale variable engagement model to get the mechanical properties of the fiber reinforced concrete under tensile loading is put forward. Meanwhile, the obtained theory value of the single fiber is done the integral on 3-D space, the forced state of the fiber concrete under tensile stress after cracking is discussed. And the functional relationship of tensile stress and crack opening displacement of the fiber concrete as well as inclined angle of fiber is described. The analytical results show that the model can preliminarily simulate the elastic pullout behaviour of inclined synthetic crack-bridging fiber, and the curve is consistent with the experimental result.