Quasi-Static Cyclic Behavior of Controlled Rocking Steel Frames

Abstract

Controlled rocking braced steel frames are seismic lateral-force resisting systems that utilize column-uplifting mechanisms, high-strength post-tensioning, and replaceable energy-dissipating fuses to enhance seismic performance. This paper describes seven quasi-static cyclic tests of half-scale rocking frames that were conducted to investigate the behavior of the system and its components, validate analysis models, establish seismic performance limit states, and develop and evaluate construction details. Design parameters investigated include alternate frame configurations, fuse characteristics, capacity for self-centering, overturning moment resistance, and initial post-tensioning stress. The tests demonstrate that the controlled rocking system can satisfy the performance goals of (1) maintaining elastic response of the rocking braced frame and post-tensioning up to drift ratios of 2.5%, (2) confining inelastic response to replaceable shear fuses, and (3) achieving near-zero residual drift when the lateral forces are removed.