Experimental and numerical study of frictional effects on block shear fracture of steel gusset plates with bolted connections

In this paper, an experimental and a numerical study has been conducted to get information about the effects of slip-critical connections in gusset plates of bolted steel tensile members. To this end, a total of 28 double gusset plates were subjected to tensile loading in seven groups, while the parameters such as the properties of specimen materials, number of bolts, amount of frictional coefficient and the type of connections were selected as experimental variables. A 3D non-linear finite element analysis was done to determine the distribution of tension and shear stresses at different times of tensile loading, showing good agreements with the results of the experiment. The results of the experimental tests and the finite element analysis showed that frictional force due to a pre-tightening force of slip-critical connections could have a significant effect on the capacity response and fracture behaviour of gusset plates under tensile loading with block shear fracture. Therefore, increasing frictional coefficient, reduction of thickness, and the resistance of specimen materials, increased the effect of frictional force on them. On the other hand, in order to evaluate the proposed equations of AISC 2016 and CSA2009 standards, as well as the proposed equations of Topkaya, C. (2004) [13] and Teh and Uz (2015) [14], for predicting the strength of block shear fracture, a comparison was done between the strengths obtained from the predictions of their equations and the strength obtained from laboratory tests. With this comparison, it was found that AISC 2016 and CSA2009 standards have the most conservative and non-conservative forecasts in the proposed equations. In addition, by changing the effective shear stress in the proposed equation of Teh and Uz (2015), from the value of 0.6Fu to Fu3, more precise predictions are provided in comparison to other equations studied in this paper, in which the main reason for its precision is better observation of the shear contribution, because this equation uses active shear planes instead of net or gross shear planes.