Shaking table test of a buckling-restrained brace outrigger system

Abstract

This study performed numerical analysis and shaking table tests to investigate the seismic performance of a damped-outrigger system with buckling-restrained braces (BRB-outrigger). A 9-m tall specimen was used to perform the shaking table tests. The specimen with the BRB-outrigger located at either the sixth or the eighth floors was tested in three phases of tests. The buckling-restrained brace (BRB) specimens were kept elastic during Phase I tests to confirm the specimen’s response under service-level earthquakes. Phase II tests utilized the ground motions similar to the friction damper–outrigger (FD–outrigger) tests for comparison. Meanwhile, Phase III tests utilized two ground motions with a peak ground acceleration of up to 1.04 g to determine whether the BRB specimens developed stable strength and exhibited energy dissipation performance under the design basis earthquake (DBE) level. In addition, this study utilized OpenSees numerical model to perform nonlinear response spectral analysis. Based on the Phase I experimental results, when compared with the specimen without equipping damped-outrigger system, the roof drifts can be reduced by around 47% to 34% when the BRB-outrigger was located at the sixth and eighth floors, respectively. During Phase III tests, the BRB specimens dissipated around 18% of the total input energy. The specimen with the BRB-outrigger located at the sixth floor performed better in reducing the floor lateral displacement responses in all three phases of tests. Based on the test results, the BRB specimens’ high strength and stable energy dissipation capacity make the BRB-outrigger specimen more capable in resisting the earthquakes above the DBE levels.