Feasibility study of TSOB replacing standard high-strength bolt in T-stub connection

Abstract

The feasibility study of T-head Square-neck One-side Bolt (TSOB) replacing Standard High-strength Bolt (SHB) in T-stub connections is conducted in this paper. Parametric analysis is carried out by means of finite element numerical simulation to reveal the effects of T-stub parameters and bolt parameters on the tensile performance of T-stub connections using SHBs and TSOBs. The plastic hinge theory is applied to explain the mechanism for the difference formation in tensile capacity between the two types of connections. The results show that the failure modes of TSOBs bolted T-stubs are the same as those of SHBs bolted T-stubs, including complete flange yielding, bolt failure with flange yielding, and bolt failure. For the failure of complete flange yielding, the tensile capacity of TSOBs bolted T-stubs is reduced by 7.2%∼16.4% compared with that of SHBs bolted T-stubs, whereas the modes of bolt failure with flange yielding and bolt failure do not cause a difference between the two types of connections in tensile response. Two modifications on design equation and design result by introducing hole type reduction factor and thickening flange for T-stub connections were proposed, respectively. The modified design methods can be used in the design of TSOBs bolted T-stubs and are identical to the design criteria of specifications Eurocode 3 and P398 for SHBs bolted T-stubs. Besides, the high-strength large hexagon nuts for steel structures and assembly classes of H12 and H13 recommended by GB/T 1229–2006 and GB/T 5277–1985 should be preferred for TSOBs bolted T-stubs. Moreover, horizontal slotted bolt holes are recommended for practical constructions, and the T-head aspect ratio of TSOB in the range of 1.6–2.0 does not affect T-stub tensile performance.