Shaking table test of a three-story frame with resilient variable friction braces

A novel resilient variable friction brace (RVFB) has been proposed to avoid the complex prestressing process of a traditional resilient brace. This study presents a shaking table test of the 1/3 scaled RVFB frame (RVFBF) to evaluate its seismic performance. In particular, the concept and mechanical model of the RVFB were introduced, including the theory of variable friction and stiffness. Then, a three-story steel RVFBF with pinned connections was designed, including one braced frame and two gravity frames. This arrangement guaranteed that the lateral force resistance was only provided by the RVFBs, while other components of the RVFBF were kept in the elastic stage. After the frame was tested under several earthquake conditions with increasing ground motion levels, the accelerations, drifts, and shear forces of the RVFBF were evaluated. The results demonstrated that the RVFB exhibited a novel flag-shaped curve with greater loading stiffness. Good agreement was verified between the mechanical and experimental results. Although the peak floor drift of the RVFBF exceeded 2.6% under the strongest ground motion level, the damage-free frame returned to the initial position with nearly zero residual displacements, and the braces had negligible performance degradation after the entire test. Therefore, a RVFBF that has satisfied seismic requirements can effectively control the structural damage and quickly restore its function after several earthquakes.