Nonlinear response of bolt groups under in-plane loading

Abstract

The use of bolted joints to connect structural members together and to transfer in-plane forces between them has been extensively employed in civil, mechanical and aeronautic structures. Most of the available methods have been developed to estimate the loading capacity but not the deformation of bolt groups. In this paper, an iterative procedure is developed to calculate the non-linear deformation of bolt groups under in-plane eccentric loads based on the assumptions of elasto-plastic behaviour of bolts and rigid body movement of the bolt group. The force exerted on each bolt is proposed to be dependent on the instantaneous centre of rotation of the bolt group. A computer program based on the above theory has been implemented to simulate the full range non-linear response of bolt groups subjected to in-plane loads, in particular, the load-slip behaviour at the inelastic range. A numerical example is given, with comparison to the non-linear finite element analysis, to illustrate the effectiveness and accuracy of the method. The behaviour of a bolt group as well as individual bolts subjected to in-plane loads was studied in detail. It was found that the ultimate capacity of the bolt group could be about 30% higher than its elastic limit. A ductility factor of 3 to 4 might be required for the bolts in a bolt group to reach their ultimate loading capacity. © 2006 Elsevier Ltd. All rights reserved.