水泥基材料中倾斜端钩型钢纤维拔出力学性能计算模型

端钩型钢纤维是结构工程中应用最广泛的钢纤维品类之一，单根钢纤维拔出力学性能对于确定钢纤维混凝土的受拉本构及受拉韧性具有重要意义。为了得到能够有效预测倾斜端钩型钢纤维拔出荷载-端部位移曲线的理论模型，首先将倾斜端钩型钢纤维拔出过程分为完全黏结、脱黏和拔出滑移阶段三种受力状态，考虑不同拔出阶段及基体孔道损伤，建立了钢纤维黏结应力与纤维端部位移之间的关系，同时考虑钢纤维塑性变形、附加摩擦力及纤维拔出角度导致的基体剥落和挤压摩擦效应，建立了一种可以预测倾斜端钩型钢纤维拔出全过程的理论计算模型，在此基础上提出形式简单的简化模型，选取已有试验数据对提出的计算模型进行验证，结果表明:本文提出的两种模型均能够有效预测端钩型钢纤维拔出全过程，具有较高的计算精度且变异系数小，为进一步分析钢纤维对水泥基材料受拉性能的增强作用提供了理论依据。 

Calculation model for pullout behavior of inclined hooked-end steel fiber in cement-based materials

It is well-known that the hooked-end steel fiber is one of the most widely-used type of steel fiber in structural engineering, and the pullout behavior of a single steel fiber is significant for determining the tensile constitutive and the tensile toughness of steel fiber reinforced concrete. In order to obtain a theoretical analysis method which can effectively predict the pullout load-end displacement curves of inclined hooked-end steel fiber, the inclined pullout process of the hooked-end steel fiber was divided into three states: fully bonding stage, debonding stage and pullout slipping stage. A novel bond shear stresses-end displacement model was established considering the different steel fiber pullout stages and the damage of the matrix hole. A theoretical analysis model that can predict the load-slip curve of the pullout behavior of inclined hooked-end steel fiber was proposed by considering the plastic deformation of the steel fiber, the additional friction, spalling and snubbing effects of the matrix caused by the fiber pullout inclination. A simplified model was also proposed based on the theoretical model. The existing experimental data were selected to verify and evaluate the proposed calculation model. The results show that the two models proposed in this paper can effectively predict the process of hooked-end steel fiber inclined pullout. And the two models have high calculation accuracy and low coefficient of variation, which provide a theoretical reference for further analysis of the effect of steel fiber on the enhancement of tensile properties of cement-based materials.