Seismic Response of a Model Moment-Frame Steel Building With Ductile-Anchor Uplifting Baseplate Connections

Abstract eng:
Several previous studies have shown that steel column baseplate connections that allow the structure to undergo rocking associated with column uplift may reduce building damage caused by strong earthquake motions. The use of concrete anchors as the ductile "fuse" to allow the uplift motion is an attractive option due to the relative ease with which the anchors may be replaced following a seismic event. More importantly, ductile-anchor column baseplate connections impart an inherently self-centering tendency to the system. In this study, we present results illustrating the robustness and practicality of the reusable anchor concept, as well as preliminary results from a program of dynamic shake-table testing of a miniature, three-story moment-frame building. The building was tested with different configurations of column baseplate connections and traditional frame fuses to allow behavior ranging from uplift-dominated to structural-hinge dominated. Configurations with ductile, uplifting baseplate connections experienced reduced seismic demands and damage, exhibiting well-delineated self-centering behavior. Under intense motions, the performance of the building was improved substantially, with significantly reduced residual drift. Mechanisms for this improved behavior, including frequency shift associated with boundary condition changes caused by anchor elongation, are discussed.

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