Shake-Table Tests of a Three-Storey Steel Structure with Resilient Slip-Friction Joints (RSFJ)

Several innovative structural systems utilizing friction dampers were tested during the ROBUST shake-table program. This paper presents 3 configurations of the Resilient Slip-Friction Joint (RSFJ) in a full-scale steel structure: as part of tension-only braces (TOB), tension-compression braces (TCB), and moment-resisting frame (MRF) joints along the structure’s length (x-direction). Symmetric friction connections (SFC) were used along the width (y-direction). Each configuration was subjected to the 1940 El Centro ground motion scaled to increasing intensities, ultimately reaching a peak ground acceleration (PGA) of 0.5g (=1.2 × design intensity). Peak displacements at the top floor were 0.66%, 0.98% and 1.26% of the total height for TOB, TCB and MRF systems respectively. The corresponding inter-storey drifts were 0.87%, 1.11% and 1.62%. RSFJ systems were essentially self-centering, with residual drifts limited to 0.03%. Peak floor accelerations were 0.67g (TOB), 0.66g (TCB) and 0.62g (MRF) in unidirectional tests. Acceleration spikes manifested in different ways, including direction reversal at peak deflection (Mode 1), sharp deceleration when joints close at the zero/upright position (Mode 1), and resonance under higher Mode 2 excitations. In bidirectional tests, slight torsion due to unbalanced SFC deformations (y-direction) and uneven loading of RSFJs (x-direction) exacerbated the deceleration, contributing to the largest accelerometer reading of 0.95g (TCB). However, peak displacements were relatively unaffected; similar responses as unidirectional tests indicate effective performance during simultaneous out-of-plane shaking. Stable RSFJ performance and absence of damage over multiple, design-level earthquakes, support their viability in low-to-medium rise structures for expediting post-earthquake functional recovery and increased resilience against earthquakes.