Numerical investigation on strength and failure modes of thread-fixed one-side bolted T-stubs under tension

The failure mechanism of thread-fixed one-side bolted T-stubs under tension was investigated by a finite element model to provide basic knowledge for its potential application in bolted beam-column endplate connection. The finite element model was verified through experimental results by considering four possible reference issues: the T-stub deformation, the force-displacement curve, the failure mode and the yield strength. Studied parameters included the bolt diameter (d), the bolt spacing (s) and the T-stub plate strength (fy). Based on numbers of plastic hinges in the T-stub flange, the failure modes were divided into three categories: Mode 1, complete flange yielding; Mode 2, flange yielding accompanied by bolt failure or hole thread failure; and Mode 3, bolt failure or hole thread failure. Furthermore, modified design equations integrating the potential hole thread failure were proposed to analyze the failure mode and the yield strength of the T-stub connection. Theoretical and numerical analyses showed that the thread hole could provide enough clamping force to fix the high strength bolt, which assured that the one-side bolted T-stub connection would not fail caused by pre-mature thread failure.