Experimental study on forming mechanism and mechanical properties of novel self-tightening one-side bolt

Abstract

In the connection of steel structures, the traditional torshear type high-strength bolt needs two operating planes, which is difficult to be applied to the connection between members with closed sections. Given the problem, a new type of professional self-tightening high-strength one-side bolt (SHSOB-PRO) was developed based on the existing SHSOB (Self-tightening High-Strength One-side Bolt). Three experiments were carried out. For the anchor end forming mechanism test, the influences of the parameters including the deformation guiding mechanisms, deformation sleeve materials, and processing technology were analyzed. For the internal force release mechanism test of the outer sleeve, the release process of the internal force of the outer sleeve was revealed, and the release mechanism of the clamping teeth-shear bearing washer was proposed. For the final forming test, the complete forming process of SHSOB-PRO was given. In addition, a series of tests on the mechanical properties were conducted, including pre-tightening force relaxation tests, tensile capacity tests, and shear behavior tests. The mechanical properties of SHSOB-PRO, including shear resistance and tensile resistance were investigated. Calculation formulas of shear capacity were given. The results illustrated that the form of the anchor end of SHSOB-PRO was stable; the pre-tightening force loss laws of SHSOB-PRO and traditional M20 torshear type high strength bolts were similar, the pre-tightening force level was slightly higher than that of the same batch of traditional torshear type bolts. The tensile capacity, and the shear capacity of SHSOB-PRO met the requirements of current Chinese specifications, indicating that the SHSOB-PRO can be applied in engineering.