ATLSS Report No. 10-09:
A self-centering concentrically-braced frame (SC-CBF) system was developed to resist earthquake loading without structural damage or residual drift. An SC-CBF is a concentrically-braced frame with column base details that permit column uplift at a specified level of lateral force. This column uplift and the subsequent rocking of the SC-CBF soften the lateral force-lateral drift behavior of the system. Vertically-oriented post-tensioning bars provide restoring force and self-centering behavior that reduces the potential for residual drift. The SC-CBF members are designed to remain elastic under the design basis earthquake. Energy dissipation elements can be used to reduce the response of the SC-CBF system.
The scope of this study includes the development of a design procedure for SC-CBF systems, a parametric study of different SC-CBF configurations, analytical and experimental studies of a large-scale SC-CBF test structure, and evaluation of the performance of the SC-CBF test structure.
A performance-based design procedure and the associated design criteria were developed for SC-CBF systems. Nonlinear dynamic analyses of several 6-story prototype buildings with different SC-CBF configurations were performed to establish the lateral force behavior of the system and to study the influence of several design parameters on this behavior. An analytical model was developed to predict the earthquake response of SC-CBF systems. Hybrid simulations of the earthquake response of a large-scale SC-CBF test structure were performed to validate the analytical model. The seismic performance of the SC-CBF test structure was evaluated with respect to the performance-based design approach and criteria.
The results of this study indicate that the SC-CBF system performs very well under earthquake loading, and that the SC-CBF is a viable alternative to conventional CBF systems. The softening of the lateral force-lateral drift response of the system was
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