Shape Memory Alloys for Seismic Response Modification: A State-of-the-Art Review

Abstract

Shape memory alloys (SMAs) are a remarkable class of metals that can offer high strength, large energy dissipation through hysteretic behavior, extraordinary strain capacity (up to 8%) with full shape recovery to zero residual strain, and a high resistance to corrosion and fatigue—aspects that are all desirable from an earthquake engineering perspective. Their various physical characteristics result from solid-solid transformation between austenite and martensite phases of the alloy that may be induced by stress or temperature. The most commercially successful SMA is a binary alloy of nickel and titanium (NiTi). Although SMAs are expensive relative to most other materials used in seismic engineering, in certain forms their capacity for high energy loss per unit volume means that comparatively small quantities can be made to be especially effective, for example when used in wire form as part of a seismic bracing system. This state-of-the-art paper presents current materials science aspects, material models, and mechanical behavior of SMAs relevant to seismic engineering, and examines the current state of design of SMA-based seismic response modification devices and their use in buildings and bridges. SMA-based devices offer promising advantages for development of next-generation seismic protection systems.