Feasibility of tension braces using Cu-Al-Mn superelastic alloy bars

Abstract

This paper investigates the feasibility of tension braces using Cu–Al–Mn superelastic alloy bars as energy dissipating and self-centering elements for steel frames by performing 1/3 scale shaking table tests. The difficulty with conventional steel tension braces lies in pinching or significant deterioration of stiffness and strength under cyclic loading. When a steel frame with conventional tension braces is subjected to intense earthquakes, pinching may lead to a large residual drift and/or instability. To overcome the difficulty, this paper examines the effectiveness of Cu–Al–Mn superelastic alloy bars, facilitated by their large recovery strain, low material cost, and high machinability, as a partial replacement of steel bars in tension braces. In the shaking table tests, a 1/3 scaled 1-bay, 1-story steel frame with the present tension braces is subjected to quasi-static cyclic loading and dynamic harmonic ground motions of 6 Hz. Both the static and dynamic test results demonstrate the effectiveness of the present braces in avoiding pinching under the ductility ratio up to 3. The dynamic test results also demonstrate the capability of the present tension braces in reducing the peak response acceleration within the base shear capacity. To study the rate dependence of the frame response, further, time-history analyses are performed by using a SDOF model based on a uniaxial rate-independent model, calibrated with the quasi-static tests. A comparison of the analytical results with the dynamic test results demonstrates that the rate dependence of the frame response is negligible up to the loading frequency of 6 Hz.