New proposal for the bending moment capacity of tubular T-joints in carbon steel and stainless steel structures

Abstract

The expected failure mode of T-joints between rectangular hollow sections subjected to bending moment with a ratio of the brace width (b1) over the chord width (b0) below 0.85 (i.e., β=b1/b0≤0.85) is the chord face failure, produced by yielding. This paper presents the development of a numerical model to reproduce this phenomenon, calibrated against experimental laboratory tests, which is then used to carry out a large parametric study, where the influence of the main geometric parameters involved in the joint resistance –the chord width (b0), the chord thickness (t0), the chord radius (R0), the brace width (b1), the brace height (h1) and the weld thickness (a)– is assessed for two different materials: S275 carbon steel and EN 1.4301 austenitic stainless steel. The results derived from the parametric study suggested that a different yield line mechanism may develop for higher β-values (β≥0.45) than that considered in current European and American codes. Hence, a new formulation for estimating the bending resistance of T-joints exhibiting chord face failure modes is presented based on a different yield line mechanism developed in this paper. This formulation includes additional geometric parameters that are dismissed in the current formulation, such as the chord radius and the weld thickness, which are found to have a non-negligible influence on the joint resistance. Moreover, the proposed formulation is adjusted in order to be used for joints with lower β-values without losing accuracy. Additionally, the new proposed formulation is adapted for stainless steel joints by combining it with the Continuous Strength Method (CSM) formulation with promising results. Finally, the soundness and safety of the proposed formulation is statistically demonstrated.