Variable-friction self-centering energy-dissipation braces (VF-SCEDBs) with NiTi SMA cables for seismic resilience

Abstract

This study introduces a Variable-Friction Self-Centering Energy-Dissipation Brace (VF-SCEDB) incorporating pre-tensioned superelastic NiTi shape memory alloy (SMA) cables and novel Variable Friction Devices (VFDs). The motivation behind the proposed member is to promote reliable energy dissipation without compromising the self-centering capability. In addition, the strength and the loading/unloading plateau stiffness of the brace can be adjusted separately by an appropriate combination of the NiTi SMA cables and the VFDs. The concept, configuration, and fundamental working principle of the VFD and VF-SCEDB are first presented. An experimental study on a proof-of-concept VF-SCEDB specimen is then conducted to understand its fundamental cyclic behavior. The results confirm that the proposed VF-SCEDB has the potential for exhibiting both excellent energy-dissipation and self-centering capabilities. Analytical models for predicting the hysteretic response of the VFD and the brace are also developed, and the prediction agrees well with the experimental results. Following the experimental program, a system-level analysis considering a series of 3-story concentrically braced steel frames employing different self-centering braces including the new VF-SCEDBs, is carried out. The results show that the frames can well control the residual deformation, but compared with other types of self-centering braces, the VF-SCEDB can more effectively reduce the peak deformation of the structures.