Hysteretic and seismic performance of dual self-centering variable friction damper braces

Abstract

A novel dual self-centering variable friction damper (DSC-VFD) brace was introduced to achieve greater post-yield stiffness and a better energy dissipation capability. To evaluate its hysteretic response with a novel flag shape, a new uniaxial material with different loading and unloading stiffnesses was developed based on the OpenSees platform in this study. The actual initial stiffness of the DSC-VFD brace was significantly lower than the theoretical value because of the tube length and pin diameter tolerances. The initial stiffness modification coefficients of the DSC-VFD brace were defined, and their calculation equations were established. Because of the uneven gap openings along the friction plates, the matrix displacement method was applied to determine the different gap openings under the tension and compression stages. Then, the hysteretic response of the DSC-VFD brace was calculated with the user-defined model; the model results were in good agreement with the experimental result, verifying the reliability of the proposed model. Simulation models were used to study the crucial parameters for the hysteretic response of the DSC-VFD brace. Finally, nonlinear dynamic analyses of a four-story braced frame were conducted to study the seismic performance of the DSC-VFD brace with a novel flag shape. The results showed that the DSC-VFD brace with a larger post-yield stiffness provided stable self-centering behavior and an effective energy dissipation capability. The high loading stiffness and energy dissipation ability effectively decreased the deformations of the braced structures and improved their seismic responses.