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

Abstract

Shake-table tests were conducted as part of the Robust Building Systems (ROBUST) program to evaluate and demonstrate the resilience of various structural concepts under earthquake excitations. This paper presents the results of 3 different configurations incorporating the Resilient Slip-Friction Joint (RSFJ) in: (1) tension-only braces (TOB), (2) tension-compression braces (TCB), and (3) moment-resisting frame (MRF) joints along the longitudinal direction. Each building configuration was subjected to the El Centro ground motion at increasing intensities, reaching a peak ground acceleration (PGA) of about 0.5 g. The peak displacements sustained were well within design values, with the top floor deflecting by 0.66%, 0.98% and 1.26% of the total height for the TOB, TCB and MRF systems respectively. The corresponding inter-storey drifts peaked at 0.87%, 1.11% and 1.62%. In all cases, the structures essentially self-centered with residual drifts limited to 0.03%. The floor accelerations observed in unidirectional tests were 0.67 g (TOB), 0.66 g (TCB) and 0.62 g (MRF). The spikes may occur during (a) direction reversal at peak Mode 1 amplitude, (b) under the influence of higher Mode 2, and/or (c) stiffness transition at the upright/plumb position. In bidirectional tests, torsion effects contributed to the largest acceleration recorded at 0.95 g (TCB). Unbalanced resistance/deformation of symmetric friction connections in the transverse direction led to the structure twisting and loading the longitudinal RSFJs unevenly. However, the effects on peak displacements were not significant and similar responses as unidirectional tests indicate effective performance under simultaneous out-of-plane shaking. The results demonstrate the RSFJ's ability to damp seismically induced vibrations and restore structures to their original, undeformed shape after earthquakes.