Quasi-Static and Dynamic Tests of a Smart Hybrid Brace

This paper presents results from two experimental programs of quasi-static testing and dynamic testing which investigate the re-centering and energy-dissipating behavior of a one-tenth-scale smart hybrid brace. Smart hybrid braces, that tend to prevent a soft-story mechanism, restore the original configuration and can be rapidly rehabilitated, are composed of three main components: (1) a set of superelastic shape memory alloy (SMA) wires anchored in a re-centering mechanism, (2) two struts with energy-absorbing capabilities, and (3) two high-strength steel tubes to guide the movement of the smart hybrid brace. A prototype smart hybrid brace was designed in compliance with the optimal proportion design methodology. The 1/10-scale smart hybrid brace was fabricated according to the similarity rules and then was tested in a uniaxial MTS 810 material testing machine. When the smart hybrid brace without the energy-dissipation struts was conducted under a series of quasi-statically cyclic tests, a double-flag-shaped hysteresis was clearly revealed. Subsequently, the energy-dissipation aluminum struts were added into the hybrid brace and then the same low-frequency cyclic tests was performed until the SMA strain approached the design strain limitation of 6%. The maximum residual displacement, 0.02 in, is smaller than the reverse transformation yield displacement of 0.03 in, meeting the proposed design concept. The hysteretic response in the last cycle exhibits a similar double-flag shape with nearly zero residual displacement, indicating that both the recentering SMA-wire mechanism and brace main body in the smart hybrid brace remain intact. The smart hybrid brace was further tested using dynamic loading with a frequency of 0.25 Hz. The dynamic results reveal a similar hysteresis to that under the quasi-static tests, except for the increased strain hardening. These tests reveal the features of the smart hybrid braces - repeatable SMA wire recentering mechanism and replaceable energy-dissipation components.