Seismic response evaluation of spring-based piston braced frames by employing closed-loop dynamic (CLD) testing

This paper employs the Closed-Loop Dynamic (CLD) testing method for evaluating the seismic response of Spring-Based Piston Braced Frames (SBPBF) by utilizing a combination of experimental and numerical approaches. The CLD testing procedure is an iterative process, which is initiated by conducting cyclic tests on a reduced-scale bracing element and followed by computational simulations of a full-scale braced frame. To this end, a hysteresis model is developed, based on testing the Spring-Based Piston Bracing (SBPB) element, which is incorporated into a simulated multi-story SBPBF. The time-dependent deformations of SBPBs under earthquake loadings are scaled down using similitude law, serving as a loading protocol for further testing and refining the hysteresis model. The developed model is then calibrated, scaled up, and integrated into the computational model to generate more precise deformation histories of the SBPB. The refined model is validated through an iterative process that combines experimental and numerical results. An illustrative example is presented to demonstrate the feasibility of the CLD testing method for SBPB archetypes. The efficiency of this approach is demonstrated by the remarkable match between the experimental and computational results. Additionally, a comparative numerical assessment is conducted on braced frames equipped with non-compressed and pre-compressed SBPBs, revealing their superior performance compared to the Buckling-Restrained Braced Frames (BRBFs).