Experimental and Numerical Investigations on the Robustness of Dissipative Joints
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Through previous research, experimental and numerical investigations performed on the innovative FREEDAM dissipative joints demonstrated the efficiency of these joints in moment-resisting frames in dissipating the seismic-induced energy. This paper presents additional experimental and numerical studies aimed at characterising the behaviour of FREEDAM joints up to failure for robustness-oriented design frameworks. Two real-scale beam-to-column joints were tested (i) under monotonic bending and (ii) under a virtual column loss scenario inducing bending moments and axial forces at the level of the tested joint. The experimental evidence emphasises the influence of the preload loss in the bolts clamping the sliding surfaces of the damper during the slippage of the joint, thus affecting both frictional and ultimate resistance. The tests confirmed the capacity of these joints to develop catenary action, ensuring significant displacement capacity under extreme loads. Numerical analyses were used to validate a simplified two-spring model (2SM) developed in previous studies. Different modelling strategies accounting for the loss of the bolt preload were assessed to ensure realistic characterisation of post-slippage behaviour—an essential aspect in robustness-related scenarios.