Experimental testing of a novel self-centring steel braced frame on the shake table in DYNLAB-IZIIS

Seismic design codes seek to limit structural displacements in order to minimise damage, but no explicit consideration is usually given to the state of the structure after the earthquake, which can be critical for re-occupancy, monetary losses and the rapidity of repair. In this paper, shake table testing of single-storey self-centring concentrically braced frame (SC-CBF) models subjected to a variety of seismic actions is presented. The aim of these tests is to assess the effectiveness of a novel self-centring system in controlling global deformation demand in CBFs, including the sensitivity of the SC-CBF response to ground motion characteristics. This system employs a post-tensioning arrangement that ensures the structure self-centres following an earthquake to minimise residual drift. A pair of brace members act as an energy dissipation system through ductile axial deformation in tension and compression. Brace member cross-section dimensions are varied between experiments to investigate a range of structural properties relevant for European design practice. A bolted connection detail facilitated the replacement of the damaged brace members after each experiment. In each experiment, table excitations are scaled to achieve increasing displacement demand and the peak drifts and residual drift are measured. The test results, including residual frame/brace deformations and rocking connection gap-openings, demonstrate the favourable self-centring characteristics of the SC-CBF under realistic earthquake excitations.