型钢-钢纤维混凝土黏结应力组成及影响因素分析

Bond Stress Composition and Analysis of Influencing Factors of Steel-steel Fiber-reinforced Concrete

为了研究型钢-钢纤维混凝土界面的黏结应力组成,以截面类型、界面锚固长度、钢纤维掺量和钢纤维混凝土保护层厚度为变化参量,完成了34根试件的推出试验,分析了试件的损伤破坏及裂缝发展形态,获得了加载端和自由端的荷载-滑移曲线。基于荷载-滑移曲线上的4种临界状态,根据界面黏结应力与外荷载的平衡关系,提出了黏结应力各组成部分的计算公式,最后分析了各因素对界面黏结应力的影响规律。研究结果表明:黏结界面的失效可分为3个阶段,即界面无损阶段、界面黏结部分失效及裂缝发展阶段、界面黏结完全失效及试件破坏阶段;型钢与钢纤维混凝土界面的黏结应力是由化学胶结应力、摩擦应力和机械咬合应力3种应力共同组成,黏结应力沿界面长度方向呈非均匀分布状态,其中化学胶结应力只存在于固定黏结扩散区;界面黏结应力组成中,化学胶结应力所占比重最大,摩擦应力次之,机械咬合应力最小;化学胶结应力随界面锚固长度的增加而减小,摩擦应力随钢纤维混凝土保护层厚度和钢纤维掺量的增加而增大,机械咬合应力随钢纤维混凝土保护层厚度的增加而增大。

In order to study the composition of interface bond stress between shape steel and steel fiber-reinforced concrete,standard push-out tests of 34 specimens were carried out by taking section type,interface embedded length,steel fiber ratio,and concrete cover thickness as parameters.The damage and crack development of the specimens were analyzed,and the load-slip curves of the loading end and free end were obtained.Based on the four critical states on the load-slip curve and the equilibrium relationship between the interface bond stress and external load,formulas for calculating the components of the interface bond stress were proposed.Finally,the influence of each factor on the interface bond stress was analyzed.The results show that the failure of the bonding interface can be divided into three stages:nondestructive stage,partial failure of bonding interface and crack development stage,and complete failure of bonding interface and specimen failure stage.The interface bond stress mainly consists of chemical bond stress,friction stress,and mechanical bite stress.The bond stress has a nonuniform distribution along the length direction,and chemical bond stress only exists in the fixed bond diffusion zone.Among the interface bond stress components,chemical bond stress accounts for the largest proportion,followed by friction stress and mechanical bite stress.Chemical bond stress decreases with the increase in the interface embedded length,friction stress increases with the increase in the concrete cover thickness and steel fiber ratio,and mechanical bite stress increases with the increase in the concrete cover thickness.