Loading rate effect on superelastic SMA-based seismic response modification devices

Abstract

The application of shape memory alloys (SMAs) to the seismic response reduction of civil engineering structures has attracted growing interest due to their self-centering feature and excellent fatigue performance. The loading rate dependence of SMAs raises a concern in the seismic analysis of SMAbased devices. However, the implementation of micromechanics-based strain-rate-dependent constitutive models in structural analysis software is rather complicated and computationally demanding. This paper investigates the feasibility of replacing complex rate-dependent models with rate-independent constitutive models for superelastic SMA elements in seismic time-history analysis. Three uniaxial constitutive models for superelastic SMAs, including one rate-dependent thermomechanical model and two rateindependent phenomenological models, are considered in this comparative study. The pros and cons of the three nonlinear constitutive models are also discussed. A parametric study of single-degree-offreedom systems with different initial periods and strength reduction factors is conducted to examine the effect of the three constitutive models on seismic simulations. Additionally, nonlinear time-history analyses of a three-story prototype steel frame building with special SMA-based damping braces are performed. Two suites of seismic records that correspond to frequent and design basis earthquakes are used as base excitations in the seismic analyses of steel-braced frames. The results of this study show that the rate-independent constitutive models, with their parameters properly tuned to dynamic test data, are able to predict the seismic responses of structures with SMA-based seismic response modification devices.

Shake table test and numerical study of self‐centering steel frame with SMA braces

“…Stable and repeatable hysteretic loops were observed. Some additional tests revealed the cyclic behavior of the Ni–Ti wires is insensitive to loading frequency over the dynamic frequency range of 0.5–4.0 Hz .…”

Local effects induced by dynamic load self-heating in NiTi wires of shape memory alloys

“…In summary, this paper reports a study of the SMA mechano‐cyclic creep and the realization of flat or S‐shaped stress (strain) curves. In this regard, the reader is also addressed to previous studies . In particular, Zhu and Zhang presented a sophisticated thermodynamic model and test results that successfully explain many phenomena reported in this paper, including self‐heating and self‐cooling in the loading process, the different slopes of thin and thick wires, and the temperature effect.…”

Hysteretic Behavior and Ultimate Energy Dissipation Capacity of Large Diameter Bars Made of Shape Memory Alloys under Seismic Loadings

“…These variations imply a decrease in the energy dissipation per cycle and in the equivalent viscous damping as the frequency of the applied loads increases. The obtained response is justified by the high dependency of SMA response on thermo-mechanical loading conditions [17][18][19]. More precisely, the self-heating of the SMA under cyclic loading and the difficulty of transferring this heat to the environment at high strain rates is responsible for the alterations observed on the shape of the hysteretic loops.…”

“…The effect of the strain rate on the amount of energy dissipated in a single cycle at ε = 6% amplitude was further investigated to identify possible differences between wires and bars made of NiTi alloys. To this end, the results obtained in this study with specimens S21 and D22 were compared with the tests conducted by other researchers [2][3][4]17] on wires and bars subjected to one cycle of amplitude ε = 6% at frequencies of 0.02 Hz and 1.0 Hz. The information regarding the SMA materials used in these studies can be summarized as follows.…”