Blast-induced ground motions (BIGM) can cause significant damage to the structure, leading to loss of life and economy. Previous studies proposed the use of base isolation system to prevent such adverse effects of blast loading on the structures. This study explores the effect of parametric uncertainty on the performance of shape memory alloy-assisted lead rubber bearing (SMA-LRB) isolator for the vibration control of building, under the BIGM. Nonlinear time-history analyses are performed to estimation responses, and compared them with the LRB isolated building. The building is modeled as a linear system, and nonlinear force–displacement behavior of LRB and SMA has been modeled via Bouc–Wen model and thermo-mechanical material model. To identify the critical design parameters and study the effect of parameter uncertainty, sensitivity analysis and Monte Carlo (MC) simulation are performed. Study results reveal that, compared to LRB, SMA-LRB reduces the peak floor acceleration by 20% with an added benefit of 35% and 67% reduction in peak and residual isolator displacement. Parametric uncertainty causes noticeable increase in mean responses of LRB isolated system than deterministic case, which get diminishes for SMA-LRB isolation system. This increase in the mean value of peak floor acceleration, peak, and residual isolator displacement are 64%, 68%, and 60% less for SMA-LRB than LRB isolated building. Further, compare to the LRB, SMA-LRB reduces standard deviation by 77% for the peak floor acceleration and peak isolator displacement, and 85% for the isolator residual displacement. Thus, conjunction of SMA with the LRB isolator enhances the performance and provides robust control effect under parameter uncertainty.
Nonlinear dampers are well known retrofitting system for the building structure, to mitigate seismic hazard. In past, among different type of nonlinear dampers, metallic yield dampers gain significant attention due to its high energy dissipation capacity. However, it has been observed while yield damper reduces floor displacement, but increases floor acceleration and leaves large residual displacement at the end of ground motion. Present study focuses on the application of shape memory alloy (SMA) dampers as an alternative to the yield damper, for retrofitting of building structure under seismic loading. Thus, response analyses are performed for nonlinear building structure without and with yield damper or SMA damper, under a large number of ground motion. Vibration control efficiency of yield and SMA damper are estimated in terms of the absolute maximum values of the floor acceleration, interstory drift ratio, and residual displacement. Response parameters are estimated over wide range of parameters of damper, building structure, and ground motion. Parametric study results revealed that yield damper provides very less acceleration control efficiency and some of cases it become more than uncontrolled structure. In contrast SMA damper slightly improves the acceleration control than yield damper (almost 14 %). In Comparison to the yield damper, SMA damper reduces the interstory drift ratio by 38 % and residual floor displacement by 47 %. Therefore, SMA damper provides major advantage in floor displacement reduction over yield damper, and acts as better re-centring device for seismic retrofitting application.
The present study focuses on the estimation of response of building structure supplemented with the superelastic shape memory alloy (SMA) damper under the stochastic seismic excitation. To this end, the stochastic response has been determined using the stochastic linearization method under random earthquakes and the control efficiency of the SMA damper is compared with the yield damper. As the response output, top floor root mean square (rms) acceleration and displacement are presented here in this study. Response analysis results show the presence of optimal values of damper strength which minimizes the responses. As observed, in this optimal condition of damper strength, compared to the yield damper, the SMA damper provided 17 % and 49 % improvements in the values of top floor rms acceleration and displacement. In the end, the parametric study has been performed under the varying strength and stiffness of the damper, time period of the structure, and earthquake excitation to establish the superior control efficiency of SMA damper over yield damper.
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