Design, Testing, and Detailed Component Modeling of a High-Capacity Self-Centering Energy-Dissipative Brace

Abstract

The self-centering energy-dissipative (SCED) brace is an innovative cross brace for buildings that provides a nonlinear response with good energy dissipation and postyield stiffness while minimizing residual drift after an earthquake. This provides a high level of seismic performance by allowing structures to remain operational even after major seismic events. Recently, the SCED brace has been improved through the design and experimental evaluation of a high-capacity SCED (HC-SCED) that has an axial capacity similar to some of the largest available conventional cross braces for buildings. This prototype HC-SCED satisfied testing protocols for buckling-restrained braces and exhibited full self-centering behavior during cycles up to 1.5% drift. To characterize the hysteretic response of the brace in detail, a new analytical approach is developed. This new approach is necessary because simplified stiffness estimates do not provide good predictions of the low-amplitude displacement response and initial effective stiffness that was measured in the full-scale experiments. The proposed analytical approach includes the effects of fabrication tolerances, which have been identified as the main reason for incorrect low-amplitude displacement predictions that result from the simplified stiffness estimates. Using the results from the HC-SCED tests, the new analytical approach provided good estimates of the initial stiffness of the braces and also was able to predict the behavior of the brace well under a larger fabrication tolerance scenario. These improved predictions may be used to improve the characterization of the effective hysteretic behavior of actual SCED braces for use in nonlinear time history analyses.