دانلود رایگان مقاله استفاده از دستگاه های منفعل هوشمند مبتنی بر آلیاژهای حافظه دار در کنترل لرزه ای سازه

ABSTRACT

In this study, seismic application of an innovative control device called self-centering hybrid damper (SCHD) is investigated. Two main characteristics of the SCHD result in structural response mitigation. Steel pipe as a vertical link and two transverse pairs of Shape Memory Alloy (SMA) wires are used as energy dissipation and recentering components, respectively. Adjustable design parameters including design load, incorporation percentage of SMA, pipe height and wire inclination angle provide desirable structural responses. A numerical parametric study revealed the effect of each parameter on device performance. Besides, an optimum incorporation percentage of SMA in design load was obtained from the parametric study. The results also indicated that in addition to ideal energy dissipation capability, SCHDs can effectively reduce the permanent displacement. Nonlinear timehistory analysis of a 5-story building equipped with the SCHD was conducted to evaluate the effectiveness of the device. The results indicated that utilization of the proposed innovative damper is an effective way in reduction of roof acceleration, peak interstory drift and permanent displacement.

7. Summary and conclusions

The research investigated the cyclic behavior of a self-centering hybrid damper which is comprised of energy dissipating and recentering components. Hysteretic behavior of SMA which resulted from numerical modeling was in good agreement with experimental results. Furthermore, parametric study was performed to evaluate the effect of design parameters on the SCHD characteristics. Results indicated that increase in wire slope unfavorably affects the flag-shaped hysteresis loop of SCHD. It should be pointed out that a methodology for optimal design of SCHDs could be one of critical improvements in this type of structural control. An optimization process was performed to obtain an incorporation percentage of SMA at which both promising properties of SCHD have ideal values. Then, the effect of cycle numbers on hysteresis loops of SCHD was investigated. The results indicated that loading under several cycles is reliable due to better representation of buckling. Embedment of hybrid damper between the beam and bracing system will concentrate the fundamental damages within these special devices. So, the main structural system is intended to have little or no damage. The outcomes of nonlinear time history analysis showed that the hybrid damper can reduce the permanent displacement, peak interstory drifts and acceleration of the seismically excited structure. Results of the investigation emphasized that performance of the steel component as an axial member could better improve the recentering property of the SCHD. Thus, further researches are essential to investigate the behavior of SCHDs with both components under axial loading. In addition, it seems necessary to confirm the numerical results experimentally.