Application of an Innovative SMA Ring Spring System for Self-Centering Steel Frames Subject to Seismic Conditions

Abstract

This paper presents an innovative shape memory alloy (SMA) ring spring system used for high-performance steel beam-to-column connections. The ring spring system, which includes a series of SMA outer rings and high-strength alloy inner rings stacked in alternation with mating tapered faces, is used in conjunction with high-strength bolts in typical extended end-plate connections to achieve favorable self-centering and energy dissipation response while ensuring ease of construction. An experimental investigation on three proof-of-concept connection specimens with varying SMA ring thicknesses and bolt preload levels is conducted first, where the key properties, including strength, stiffness, ductility, self-centering capability, and energy dissipation, are discussed in detail. Following the experimental program, a three-dimensional (3D) numerical study is carried out that enables a more in-depth interpretation of the test results and supports the design of full-scale self-centering connections for a prototype steel moment frame. A system-level time-history analysis is then performed on the frame with various layouts of the SMA connections, and it is shown that, compared with a conventional steel frame, the structure with the SMA connections exhibits comparable maximum interstory drifts but significantly reduced residual drifts. The results also reveal that a reasonable balance between structural performance and cost may be achieved by an appropriate arrangement of the SMA connections within the structure.