Testing of steel bolted T‐stub end‐plate joints with spherical washers subjected to tension

Abstract

Preliminary results of experimental research conducted on an end‐plate joint of two bolted T‐stub components subjected to tension are presented in this paper. The research was oriented on qualitative verification of such joint behavior when fitted with spherical washers. Analysis was conducted to evaluate the efficiency of such washers in minimizing bolt bending induced by various types of geometrical and material imperfections. These imperfections result in the loads applied off bolt axis and are further amplified by the potential prying effect. Joints made of S355 structural steel, differing in the end‐plate thickness (12, 15 and 16 mm), bolted with two class 5.8 M16 bolts distributed symmetrically with respect to the vertical axis of the joint, not prestressed but with controlled tightening torque, have been applied. It has been shown that application of a spherical washer may significantly increase the bearing capacity of a joint subject to tension, when compared against similar joint fitted with typical flat washers. However this increase in bearing capacity is obtained at the expense of significant deterioration in ductile properties of the material, thus inducing a risk of brittle fracture, which may be difficult to accept by the potential user, as this destruction mode occurs rapidly and is not preceded by any signs of imminent danger.