دانلود رایگان مقاله معادل خطی مدل الاستیک چسبناک آلیاژ حافظه دار

Abstract

In this investigation, the equivalent linear elastic-viscous model of shape memory alloy (SMA) is established for seismic analysis of base-isolated structures using system identification method. The necessary key parameters to express the hysteresis loop of SMA are austenite stiffness, transformation strength, ductility ratio, and stiffness ratio. These parameters are considered in the modeling. This model is developed based on the American Association of State Highway and Transportation Officials (AASHTO) isolation guidelines. In order to validate the proposed model, the base-isolated benchmark building is analyzed by using proposed equivalent linear SMA model as well as the different non-linear SMA models. The evaluation criteria given in the benchmark problem and time variation of top-floor absolute accelerations and base-displacements are considered for comparing the linear and nonlinear models of SMA. An excellent agreement is achieved between proposed equivalent linear SMA model and its nonlinear models. The seismic code recommends that the equivalent linear model of the nonlinear system can be used for carry out the response spectrum analysis of base-isolated structures. Furthermore, the non-linear model requires computationally more time and effort, especially for larger degrees of freedom system. The proposed model may be useful to design engineers in order to over come the disadvantage of non-linear models.

6. Conclusions

The response of the base-isolated benchmark building with SMA supplemented ERB isolation systems is carried out by time history analysis. An equivalent elastic-viscous model of SMA is proposed to simulate the nonlinear behavior of SMA. From the present study, following conclusions can be drawn. 1. The effective stiffness of nonlinear SMA model shows similar pattern as that of bilinear model. Therefore, the AASHTO isolation guidelines for bi-linear system can be used for effective stiffness of nonlinear SMA model. 2. Nonlinear SMA models and the proposed equivalent linear model shows the comparable peak response of the base isolated benchmark building. 3. As the proposed equivalent linear model is established by using system identification method, this model is valid for any type of isolated structures (i.e. Bridges, Buildings, Water tanks etc.). 4. Both nonlinear G-C and G-C’s extended model show almost similar response at larger displacement. This may be attributed to the insignificant difference between the estimated hysteresis area by these two models. 5. The proposed equivalent linear model of SMA is a modified form of AASHTO guidelines specifications, and therefore practicing engineers can freely use it in the design.