Effect of hysteretic properties of SMAs on seismic behavior of self-centering concentrically braced frames

Abstract

Summary Shape memory alloys (SMAs) exhibit nearly ideal superelastic properties when the ambient temperature is above the austenite finish temperature, which enables them to recover deformation and dissipate energy for the seismic‐resisting structures. This unique hysteretic properties of SMAs indicate they are very promising in developing self‐centering structures. As such, recent studies installed SMAs in concentrically braced frames (CBFs) to form SMA‐based self‐centering CBFs (SCCBFs) and illustrated that the structures performed excellently with controlled peak drift and eliminated residual drift upon earthquakes. SMAs show variability in the hysteretic parameters due to the difference in metal types, crystallographic structure, component ratios, and heating treatments in producing process. Thus, this necessitates an investigation into the associated effect on the seismic performance of SMA‐based SCCBFs. To this end, this study selects 3 SMAs, proposes a bracing form, and installs SMA braces in the CBFs. Prior to the seismic analysis, all 3 frames are designed by an ad hoc design method. The focus of this paper is to understand the effect of hysteretic properties on the seismic behavior of SMA‐based SCCBFs. Intensive nonlinear time history analyses are carried out to assess the seismic performance of these structures under frequently occurred earthquakes and design basis earthquakes. The analytical results indicate the properly designed SCCBFs are able to meet prescribed performance targets and display comparable seismic demands, irrespective of the SMA types. This study suggests that using SMAs with greater hysteretic parameters is more favorable, from the perspective of saving material consumption and controlling acceleration demands.

Manufacturing and performance of a novel self‐centring damper with shape memory alloy ring springs for seismic resilience

“…The experimental results demonstrated that the dampers were effective in reducing both the peak and residual deformation of the structure subjected to strong earthquakes. Apart from damping systems, SMAs have also been considered in other seismic resistant devices and members, including braces, beam‐to‐column connections, base isolators, and bridges …”

“…The experimental results demonstrated that the dampers were effective in reducing both the peak and residual deformation of the structure subjected to strong earthquakes. Apart from damping systems, SMAs have also been considered in other seismic resistant devices and members, including braces, [14][15][16][17] beam-to-column connections, [18][19][20][21][22][23][24] base isolators, 25,26 and bridges. 27,28 Although the wire form of SMA has proven to be effective in providing energy dissipation and self-centring capability, there are still practical issues such as difficulty of gripping (especially when a large number of wires are to be included) and vulnerability to fracture at the gripping region due to local stress concentration.…”

Influence of shape memory alloy brace design parameters on seismic performance of self‐centering steel frame buildings

“…SMA bracing systems have commonly been designed such that SMA elements are subjected to deformations within the superelastic strain limits of the SMA material. In numerical studies, it has been assumed that the SMA elements exhibit a linear strain hardening behavior when the strain in SMAs are over superelastic limit . Although this approach can be considered as a valid approach to evaluate the performance of buildings with SMA braces under seismic hazard levels considered in design codes, the ultimate state of SMA elements needs to be included in the modeling when the collapse performance of structures is assessed.…”

“…In numerical studies, it has been assumed that the SMA elements exhibit a linear strain hardening behavior when the strain in SMAs are over superelastic limit. 12,13,31,32 Although this approach can be considered as a valid approach to evaluate the performance of buildings with SMA braces under seismic hazard levels considered in design codes, the ultimate state of SMA elements needs to be included in the modeling when the collapse performance of structures is assessed. This paper investigates the effect of design parameters of SMA cable braces into the seismic and collapse performance of SMA-braced steel frame buildings.…”

Modified direct displacement‐based design approach for structures equipped with fluid viscous damper

“…However, this method can be also used for design of structures by performing a series of designs and evaluations in an iterative manner that this iterative design approach causes a high computational cost and time . To achieve a predictable and desirable performance level without iteration in the design process, different performance‐based design methods such as direct displacement‐based design (DDBD) and performance‐based plastic design have been proposed. The aim of these design approaches is to achieve a target story drift under a specific level of seismic hazard.…”