焊钉连接件直径对钢-HSSFC界面受剪性能的影响

为研究大直径焊钉连接件在高强钢纤维混凝土(HSSFC)中的力学性能,制作了4组共12个焊钉连接件进行推出试验,得到了不同直径焊钉连接件在HSSFC中的破坏形态、抗剪承载力和极限滑移量,并对规范承载力公式进行了修正。结果表明:对于16和19 mm的小直径焊钉连接件,破坏形式以焊钉剪断为主; 对于22和25 mm的大直径焊钉连接件,破坏形式以焊缝破坏为主; 与普通混凝土推出试件相比,采用HSSFC时,焊钉连接件的承载力有一定的提高; 随着焊钉直径的增大,推出试件的抗剪刚度有较大的提高,极限滑移量则明显减小。对既有规范给定的焊钉连接件承载力计算公式进行了修正,修正后的公式与试验值吻合较好,与收集到的92个采用不同类型混凝土、不同强度等级(C60～C100)、不同焊钉直径(16～30 mm)的推出试件试验值均较为吻合,表明该修正公式适用范围较广,可作为钢-HSSFC大直径焊钉剪力键的设计参考。
In order to study the mechanical behavior of large diameter shear stud connectors in high strength steel fiber reinforced concrete(HSSFC), 12 push-out specimens of 4 groups were prepared and tested. The influences of different stud diameters on failure mode, shear bearing capacity and ultimate slip were investigated. The tested results show that shear stud connectors with the diameters of 16 mm and 19 mm are shank failure and no cracks are found on the surface of the concrete slab. However, for large diameter shear stud connectors, the failure mode is changed to welding fracture, and the cracks are developed on concrete slab with the increase in shear bearing capacity, but the crack width is small, and the steel fiber reinforcement can hinder crack propagation. The shear bearing capacity of stud in the HSSFC is almost the same to that in normal concrete because the influences on the shear bearing capacity can be neglected when the strength of concrete is sufficiently high compared with the strength of shear stud. In addition, the ultimate slip decreases with the increase in stud diameter and it is lower when compared with that which uses normal concrete, so the steel fiber can constrain the slip and effects of the restriction are more obvious when the stud diameter is high. The shear stiffness of normal concrete specimen is greatly improved, such as the shear stiffness of stud with diameter of 22 mm is twice that in normal concrete. The higher the diameter of stud is, the greater the increase in shear stiffness is. At last, the paper modifies the formula proposed by design code, and the modified formula better fits with the collected 92 test results which include different types of concrete, strength grade ranges from C60 to C100 and different diameter ranges of shear stud from 16 mm to 30 mm