Bidirectional Cyclic Loading Performance of a Prefabricated Self-Centering Metallic-Damped Steel Column Base

Abstract

A prefabricated seismic-resilient steel column base capable of accommodating bidirectional loading, enabling fast onsite construction and causing minimal disturbance to building function, is proposed. The column base consists of a lower circular column segment embedded in foundation, an upper box column segment placed above ground floor, four buckling-restrained steel plates (BRPs) as energy-dissipating devices to connect the column segments, and a pretensioned high-strength steel rod anchored between the column segments to secure self-centering. The upper column segment is supported on the lower one via a pair of circular base plates with protruded fillet edges to allow upper column rocking in any direction, and they are pretensioned in shop as a prefabricated column to expedite onsite construction. Theoretical models of the proposed column base under unidirectional and bidirectional seismic loading are developed, and design criteria for different seismic intensity levels are presented. A cyclic test program of a full-scale column specimen with the proposed configuration subjected to one unidirectional and three bidirectional loading phases is introduced. Global and local responses of the specimen are discussed, and test results confirmed effectiveness of the column base providing sufficient rigidity under service level earthquakes, repeatable hysteresis under bidirectional loading, avoiding rupture of the BRPs under series of strong earthquakes, and achieving self-centering, low-damage, and rapid postearthquake recovery. The theoretical models and design criteria to achieve the expected performance under bidirectional loading are validated.