Bearing behavior of multi-bolt high strength steel connections

Abstract

This paper presents an experimental and numerical investigation on the bearing behavior of multi-bolt high strength steel connections in single bolt line. Three grades of high strength steel with nominal yield stress of 550 MPa, 690 MPa and 890 MPa were used to fabricate thirty lap connections with two or three bolts. It is found that the deformation capability of high strength steel plate near bolt hole is sufficient to meet the deformation demand of compatibility in multi-bolt connection even with an intended bolt hole misalignment of 2 mm for M24 high strength bolt. The comparison with Eurocode3 and AISC 360-16 is conducted. When no partial or safety factors are considered, the original formulae of Eurocode3 already has sufficient safety while AISC 360-16 gives unsafe predictions. Numerical models were established and verified by test results. With the obtained results, the full-range distribution of internal load among different bolts can be divided into four stages. Features for each stage are summarized and the effect of bolt hole misalignment on the distribution pattern is evaluated. Numerical analysis results indicate that, behavior of an individual bolt in multi-bolt connection may be influenced by surrounding bolts. The formation of critical yielding band between different bolts may explain this influence. Based on the experimental and numerical analyses, this paper proposed a new ultimate bearing resistance model for multi-bolt connections. The proposed model is capable of describing the nonlinearity in the ultimate bearing resistance of multi-bolt connection and achieves improved predicting accuracy compared to classical models.