Comprehensive studies on the behaviors of high strength steel T-stubs with thin-walled flange at elevated temperatures

This paper presents the experimental, numerical, and theoretical studies aimed at investigating the fire behaviors of high strength Q690 steel T-stub connections. The experiments determined failure modes, load–displacement curves, ultimate displacement, ductility factors, and load capacities of the specimens at elevated temperatures. The rupture of the flange disappeared at temperatures exceeding 600 °C. A finite element model was established using ABAQUS software, validated by the experimental results, to explore the effect of bolt preload and bolt grade on the fire behaviors of T-stubs. The first yield resistance derived from experimental and numerical findings was compared with EC3 predictions, highlighting a severe underestimation by EC3 for high-strength steel T-stubs with thin-walled flanges. A theoretical model was subsequently proposed and validated against numerical and experimental outcomes, serving as the basis for a novel design method. This model accurately anticipates the progression of the plastic hinge line and the first yield resistance, suggesting the use of 2.0% yield strength of high-strength steel to calculate the first yield resistance of steel T-stubs. •Tension test on high strength steel T-stub connections at elevated temperature were carried out.•Finite element model on T-stub connection were established and validated by test data.•Parametric studies were conducted to quantitatively assess the influence of key factors on capacity of T-stub connection.•The load capacity of T-stub connection predicted by EC3 were evaluated and design methods were proposed.