Design Concepts for Controlled Rocking of Self-Centering Steel-Braced Frames

Abstract

The self-centering rocking steel-braced frame is a high-performance system that can prevent major structural damage and minimize residual drifts during large earthquakes. It consists of braced steel frames that are designed to remain elastic and allowed to rock off their foundation. Overturning resistance is provided by elastic post-tensioning, which provides a reliable self-centering restoring force, and replaceable structural fuses that dissipate energy. The design concepts of this system are examined and contrasted with other conventional and self-centering seismic force resisting systems. Equations to predict the load-deformation behavior of the rocking system are developed. Key limit states are investigated including desired sequence of limit states and methods to help ensure reliable performance. Generalized design methods for controlling the limit states are developed. The design concepts are then applied to a six-story prototype structure to illustrate application of the rocking steel frame system and provide the framework for a coordinated research program to further develop and validate the concepts.