Effect of structural and seismic uncertainties on the performance of steel buckling-restrained braced frames equipped with intelligent materials

Uncertainty of design parameters is one of the most important variables in determining the reliability of structures. In the design and analysis of steel frames, buckling-restrained brace (BRB) equipped with intelligent materials such as shape memory alloy (SMA), there are various variables such as gravity loads, lateral loads, material properties, and geometrical specifications that the uncertainty of each of which can have a significant effect on the safety of the structure. In this research, considering the existing uncertainties in material properties, loading and geometry of members, the reliability of steel BRB frames equipped with intelligent materials has been investigated. Evaluation of sensitivity and reliability analyses based on kriging meta-model of BRB frames with and without SMAs under artificial near-fault earthquakes are conducted. For this purpose, two frames 5 and 15-story with BRB with and without SMA have been studied under 9 artificial near-fault earthquakes. Nonlinear dynamic analyses were performed using OpenSees software and reliability analyses were performed by linking MATLAB software on frames. The results of this research showed that in the studied frames, the random variables of the length of SMA and the cross-sectional area of the BRB were the most effective variables in calculating the probability of failure in BRB frames with and without intelligent materials, respectively. Also, by increasing the height of the frames, the reliability index has decreased. For example, the reliability index of a 5-story BRB frame with SMA has decreased by approximately 17% compared to a 15-story frame. Meanwhile, the maximum values of the reliability index using SMA in 5 and 15-story frames have increased by 10 and 6%, respectively.