M. Ghassemieh, H. Salahshoor, University of Tehran, Tehran, Iran
One of the main desirable behaviors of structures meanwhile earthquakes and lateral loadings, to avoid great damages, is to provide the recentering behavior [is to make the structure behave through a recentring manner]. So, developing damping and energy dissipating systems such as bracings which cause this effect will be very beneficial, especially for repair and retrofitting of structures.
Basically, Recentering effects are taken up via complicated and sophisticated mechanisms, via smart devices. Considering the fact that such systems are needy to outer supporting mechanisms to provide the decent objective structural manner. If we can make this recentering effect as the innate behavior of the structure it would be very desirable, so using materials which cause this recentering effect will be of high value. Shape memory alloys are a kind of smart materials. These materials have two extraordinary behaviors: Shape memory effects and Superelasticity. These two behaviors occur in different temperatures.
This paper, have focused on bracing systems with shape memory alloys considering their superelastic behavior, which are applied to structures that have been modeled according to old standards. This superelastic effect provides the desirable recentering behavior in the structure. Different kinds of structures including steel structures and reinforced concrete structures have been modeled. Shape memory alloys will cause less residual displacements in the structures. Different kinds of bracing systems have been tested. Many static and dynamic time-history analysis have been tested via finite element method. This study results that: structures with shape memory alloy bracings have more displacements during the earthquake but less residual displacement in comparison with structures with steel bracings, so SMAs cause less damages produced by residual displacements.
Summary: In this paper two existing structures have been modeled. One of them is a concrete structure and the other is a steel structure. these structures have been retrofitted via bracing systems. These bracings once have been modeled with shape memory alloys and once with steel. the model have been tested under different dynamic time-history excitaions and the results have been compared. the analysis are done using finite element method. the results show that the structure with SMA bracings have less residual displacements in comparison with the system with steel system.
