Innovative use of a shape memory alloy ring spring system for self-centering connections

Abstract

This paper presents superelastic shape memory alloy (SMA) ring spring systems for seismic applications. The study commences with an experimental investigation looking into the mechanical performance of individual SMA ring springs under cyclic loading. The strength, self-centering ability, and energy dissipation capacity are shown to be dependent on the ring size as well as the treatment of the contacting taper face. Subsequently, a proof-of-concept beam-to-column self-centering connection is physically tested, shedding further light on the practical application of the ring spring systems for high-performance seismic resisting steel frames. The connection shows favorable cyclic behavior, with the majority of the deformation demand resisted by the SMA ring spring systems. The remaining structural components generally stay undamaged. Driven by the superelastic behavior of SMA, excellent self-centering ability with satisfactory energy dissipation is exhibited. A numerical investigation is then conducted to gain a further understanding of the load resistance mechanism of the proposed connection. The numerical model is validated against the experimental results with good agreement observed, enabling a further parametric study to be conducted taking a more in-depth look into the influence of ring pre-compression, taper face friction, ring size, and shear tab bolt preload on the overall performance of the connection. Based on the test and numerical data, some design comments are also made.