Behaviour of welded lean duplex stainless steel T-stub components under varying loading rates
Abstract
This study presents the first systematic investigation of the strain rate dependent response of welded lean duplex stainless steel T-stub components through an integrated experimental and numerical modelling programme. Twenty-four T-stub specimens incorporating M16 and M20 fully threaded A4 – 70 and DX109 bolts were tested under quasi-static loading and loading rates varying from 10 mm/s to 75mm/s. Coupon and bolt-nut assembly tests were conducted to quantify material strain rate sensitivity. The results demonstrate clear positive strain rate effects on strength for both flange plates and bolts, leading to increases of up to 15% in equivalent yield resistance at the T-stub component level, while deformation capacity and energy dissipation decrease. Bolt spacing governs stiffness, resistance and prying action, while loading rate has limited influence on prying development prior to peak load. A finite element model was developed and validated against the experimental tests; it was used to reproduce the full range response including fracture with high degree of accuracy. An improved method for predicting the moment capacity of the flange consistent with the plastic resistance of the T-stub based on a strain limit approach, incorporating the effects of strain hardening and loading rate, is proposed. The method provides a rational basis for predicting the plastic resistance of stainless steel T-stub connections under both static and elevated loading rate tensile actions, enabling more reliable assessment of connection robustness under extreme loading conditions.