Experimental investigation and seismic analysis of a novel self-centering piston-based bracing archetype with polyurethane cores

This paper introduces a novel self-centering Piston-based Bracing with Polyurethane Cores (PBPC) as a passive seismic control device. Frames fitted with such bracing elements will be able to mitigate the loss of life, post-earthquake repair costs, and downtime recovery after a major seismic event. The proposed earthquake-resistant archetype integrates a steel shaft, steel tubes, and hollow and solid polyurethane (PU) cylindrical cores. The PU cylinders are activated using a bracing shaft and dissipate seismic energy with a self-centering response. A set of unidirectional cyclic tests were conducted on a scaled PBPC specimen to quantify the effects of pre-compression force level, loading rate, and past loading history. The pre-compressed force curtailed the undesirable viscoelastic deformation and the energy dissipation capacity of PU cores. The non– and pre-compressed PBPC elements exhibited large deformability and adequate energy dissipation; nonetheless, they recovered their initial conditions with stable flag-shaped hysteresis loops following successive compression cycles. Additionally, a new material model was developed in OpenSees software for PBPC and a comparative seismic analysis was conducted. The simulation outcomes supported by experimental data proved the efficiency of the frame fitted with PBPCs in mitigating damage compared with a buckling-restrained braced frame.