Development and Testing of New Ring Spring Self-Centering Energy Dissipative (RS-SCED) Braces for Seismic Resilience of Buildings and Bridges

The applicability of existing SCED braces is limited by size, as well as load and deformation capacity. In this study a new compact Self-Centering Energy-Dissipative (SCED) brace is developed, designed, and experimentally tested. The new innovative compact high capacity ring spring SCED (RS-SCED) is a brace system that exhibits a nonlinear response with good energy dissipation and post-yield stiffness, while eliminating or minimizing residual drift after an earthquake. The new high capacity compact RS-SCED brace utilizes ring springs to provide a restoring force, while simultaneously dissipating energy through friction between ring spring units in the assembly. The new RS-SCED brace has high load capacity with stable and repeatable hysteresis that makes them suitable for deployment in full scale building and bridge structures in high seismic regions. Hybrid simulations are performed to evaluate the system level performance of the new brace in prototype structures. In this study, a 4-storey building and a 3-span bridge with the new ring spring SCED brace are tested using hybrid simulations. The physical test substructure is the prototype compact high capacity ring spring SCED with a load capacity of 1400 kN and a deformation capacity of 160 mm. During the tests, the systems are subjected to a series of earthquake records with a wide range of frequency contents at different hazard levels. Typical seismic design procedures rely on ductility and overstrength factors for simplified seismic analysis and design using an equivalent static force procedure. In this study, the FEMA P695 methodology is used to determine the ductility (R), overstrength (Ω_0) and deflection amplification (C_d) factors for seismic design of the proposed structural system. The combination of different building heights, bay sizes and seismicity levels led to the design of 12 different prototype building designs for the numerical analyses. Pushover analyses, as well as nonlinear dynamic time history analyses of the prototype buildings subjected to a suite of scaled ground motions are performed. The calibration of the seismic design factors for the RS-SCED braced frame buildings, is based on optimization of the seismic performance of buildings by considering the peak storey drifts, residual drift and floor accelerations.