An SMA cable-based negative stiffness seismic isolator: Development, experimental characterization, and numerical modeling

Abstract

Shape memory alloy (SMA)-based seismic isolation systems can successfully reduce the peak and residual displacements of bridges during strong earthquake, but they commonly lead to an increased force demands in substructure. This study explores the development of an SMA cable-based negative stiffness isolator to alleviate this problem. The proposed isolator is composed of superelastic SMA cables and a frictional sliding bearing with convex surfaces. The frictional sliding bearing limit the forces transferred to the superstructure and provides energy dissipation, while its built-in negative stiffness mechanism reduces the force demands in substructure. SMA cables provide critical restoring forces, additional energy dissipation, and displacement-limiting capacity. Based on the force balance, the negative stiffness and restoring requirements of the SMA cable-based negative stiffness isolator were analyzed first. Then, a prototype large-scale isolator was designed and fabricated. Next, the experimental testing of the developed isolator was performed under two different vertical load levels. Finally, finite element modeling of the proposed isolator was conducted, and the simulation results and experimental results were compared and discussed. The proposed isolator generates lower forces than the SMA-based zero and positive stiffness isolators and can exhibit stable energy dissipation capabilities with very good displacement-limiting and self-centering capabilities.

A hybrid self-centering seismic damper: Finite element modeling and parametric analysis

“…More recently, large-diameter SMA cables enabled the development of large-scale SMA-based seismic control devices and bracing systems (Cao et al, 2020, 2022a, 2022b; Chen et al, 2020; Liang et al, 2020; Peng et al, 2021, 2022; Shi et al, 2020a, 2020b). SMA cables consists of multiple individual wires and can resist high level of tensile forces without any sacrifice on superelastic characteristics of SMA materials.…”

Design, manufacturing, and testing of a hybrid self‐centering brace for seismic resilience of buildings

“…There have been various efforts to leverage these unique capabilities offered by superelastic SMAs to develop seismic protection technologies such as dampers, [6][7][8] bracing systems, [9][10][11] connections, [12][13][14][15][16][17][18] and isolators. [19][20][21][22] Although SMAs provide some level of energy dissipation, the equivalent viscous damping obtained from SMA-only devices is commonly below 5%. 9 Therefore, several hybrid devices have been proposed by combining different forms of SMAs with other supplemental energy dissipating elements to augment their damping capacity.…”

“…There have been various efforts to leverage these unique capabilities offered by superelastic SMAs to develop seismic protection technologies such as dampers, 6–8 bracing systems, 9–11 connections, 12–18 and isolators 19–22 . Although SMAs provide some level of energy dissipation, the equivalent viscous damping obtained from SMA‐only devices is commonly below 5% 9 .…”

Study on Damping Performance of Hyperboloid Damper with SMA-Negative Stiffness

“…To reduce the internal force of SMA, Refs. [17][18][19][20] and Wang and Cao [21] proposed the multi-level fortified SMA lead bearing, which can reduce the structural internal force under moderate and strong earthquakes to a certain extent; the test shows that SMA has strong resilience. Han et al [22] proposed a variable curvature SMA friction.…”