Experimental investigation and modelling of T-stubs undergoing large displacements

This paper investigates the development of second (2nd) order effects, arising from geometric and material non-linearities of T-stubs bolted to a rigid support, through a combination of experimental, numerical and analytical approaches. Experimental data is presented for a broad range of T-stub geometries, designed to ensure that significant 2nd order effects always develop, that will complement the existing library of limited test results. Finite element models, incorporating combined tensile (ductile) and shear damage initiation, evolution and failure in both the flange and bolt, are also developed to elucidate how key geometric/material parameters influence the resistance and ductility of T-stubs undergoing large displacement. It will be shown that the restraining effect from the bolt is integral to the activation of catenary action in the flange and the development of a second hardening branch in the tensile response, leading to identification of two new modes of failure that are not currently considered in classical theory or by EC3 (Part 1.8). A mechanical model is formulated to identify the key geometric and material parameters controlling the initiation, and development, of the second hardening branch. Finally, a criterion is proposed to estimate the critical displacement from when 2nd order effects become active.