Investigation into prying force and bolt moment in bolted steel T-stubs

A common characteristic of the behaviour of steel T-stubs subjected to tensile loading is the prying effects which can develop as a result of the deformation of the flanges of the T-stub. Prying effects can induce a substantial increase in bolt forces as well as the flexural engagement of the bolts. Although the T-stub model has been extensively investigated over the years and led to design predictions in terms of strength and stiffness, the flexural engagement of bolts has been disregarded in most studies that investigated prying in bolted T-stubs. Consequently, the actual codes do not account for the bending moment in the bolts. However, the combined action of tension and bending may induce substantial stresses in the bolts and cause premature failure. In this work, an extensive parametrical study was carried out on welded plate T-stubs to investigate prying action. Experimental data from the literature was used to calibrate and validate advanced FE models that were constructed in ABAQUS. Good agreement was obtained, and a large number of FE models were generated to study the influence of different material and geometrical parameters such as flange thickness, edge distance, gauge distance, bolt diameter, steel grade, and bolt class. Various values related to prying effects such as the total bolt force, prying force, bolt moment, and the position of the resultant of contact forces were investigated. The novelty of this study was the focus on the bending moment that may develop in the bolts. Through a curve fitting process using the results from the parametrical study, a formula was proposed for the evaluation of the prying force and the bolt bending moment.