Experimental and numerical study of the slip factor for G350-steel bolted connections

In current practice the shear load-slip behaviour of bolted steel connections is estimated based on the friction coefficient and bolt preload. The friction coefficient is approximated by the slip factor, which is determined experimentally through testing of standard specimens. A linear load-slip (F-d) behaviour is typically assumed, with an arbitrary initial stiffness depending on the slip load and an assumed slip displacement. However, even for the standard slip factor test specimens, the F-d behaviour in the initial stage is not necessarily linear. To enable the development of more accurate models for bolted steel connections, it is essential to understand the F-d behaviour of standard specimens constructed using AS/NZS 3678-350 steel, known as G350, a common Australian steel with limited data in the current literature. An experimental program was performed to investigate the effect of surface finish on the shear behaviour. In addition, numerical simulation was carried out and the results were compared with the experimental results including the F-d behaviour. An empirical formula was proposed for the initial slip behaviour and a good fit was demonstrated. The improved understanding of the shear behaviour could be applied to the design of connections for modular buildings which provide suitable site assembly tolerances while controlling the possible cumulative slip displacement.