Optimization of SMA based damped outrigger structure under uncertainty

Abstract

Outriggers have been proven to be an efficient system to reduce the dynamic responses of core-tube type high-rise buildings by utilizing the axial stiffness of the peripheral columns. However, outer columns and outriggers are subjected to excessive lateral force demands. To reduce the demand, the damped outrigger is used where dampers are installed between the perimeter columns and outriggers. To improve the performance and enhance the residual deformation, in this paper, the use of shape memory alloy (SMA) springs is introduced to dissipate energy. The SMA dissipates energy through a hysteretic phase transformation of its microstructure triggered by cyclic loading. In the mathematical model implementation, the nonlinear behavior of superelastic SMA is linearized by the stochastic equivalent linearization method. Stochastic uncertainty in the ground motion is considered, and the performance is assessed by minimizing the failure probability of the structure. To solve the optimization problem, Kriging is used as a surrogate model. For better accuracy of the surrogate model, an efficient global optimization scheme is used. The purpose of the optimization adopted in this study is to find optimal design parameters associated with the initial stiffness of the SMA and the location of the outrigger. The results clearly demonstrated the efficacy of the proposed SMA based outrigger.