Dynamic Response Analysis of a Frame Structure with Superelastic Nitinol SMA Helical Spring Braces for Vibration Reduction

Abstract

This paper proposes a new type of energy dissipation brace system that is composed of superelastic Nitinol shape memory alloy (SMA) helical springs to reduce seismic responses of a frame structure. To investigate the earthquake-resistant effectiveness of the proposed brace system, a 2-story steel frame structural model was fabricated, and four SMA springs were trained in the laboratory. To describe the nonlinear force-displacement relationship of the SMA helical springs under general dynamic load, a mathematical model was developed based on a stress-strain relationship of SMA material, and the model agreed well with the test results. A numerical simulation model of the 2-story frame with the new energy dissipation brace system was then established to obtain the responses of the frame subjected to an earthquake. To verify the effectiveness of the numerical model, a series of vibration table experiments were carried out. The experimental results have very good agreement with the numerical simulation results, and the proposed brace system can effectively suppress structural vibrations. Compared with the steel spring brace and the viscous damper brace, the new energy dissipation brace can provide better vibration reduction effects, simultaneously reducing the displacement and acceleration responses of the frame. Considering its abilities of energy dissipation as well as fully recentering, the Nitinol SMA spring brace system has a great potential for frame structural vibration reduction.