Proportioning of self‐centering energy dissipative braces

Self‐centering energy dissipative (SCED) braces are designed to limit the maximum story drifts in buildings during earthquakes and to nearly eliminate residual drifts. The key properties of conventional braces (eg, strength, stiffness) can be determined with current seismic design procedures, but additional criteria are needed to select the hysteretic properties of SCED braces (eg, prestressing level, fuse activating deformation). Past investigations of the seismic performance of the SCED braced frames selected brace characteristics to match the hysteretic characteristics of buckling restrained braces (BRB). However, those characteristics may not be achieved because the performance of the SCED system is constrained by the elongation capacity of the post‐tensioned tendons. To develop recommendations for proportioning SCED braces, the researchers conducted a parametric study on the properties of two typical SCED systems, using a nine‐story steel braced frame office building. The seismic performances of the SCED systems were then compared with that of a BRB system including an analysis without property uncertainty and an analysis with uncertainty using Monte Carlo simulation. Based on the cost and seismic performances of SCED systems designed using various characteristics, recommendations are proposed for proportioning the SCED systems. Besides having much smaller residual drifts, the SCED systems had a smaller likelihood of exceeding a maximum story drift of 3% and less drift concentration compared with the BRB system, though they generated larger floor accelerations and forces in connections and adjacent members. The property uncertainty increased the residual drift of the SCED systems.