Seismic performance of steel braced frames with self‐centering buckling‐restrained brace utilizing superelastic shape memory alloys

Abstract

Buckling-restrained braced frame (BRB) is one of the newest seismic force-resisting systems used in buildings. However, one of the requirements for designing a structure is to provide a ductility behavior of structures to dissipate earthquake energy and to avoid residual drifts. These days, self-centering seismic lateral force-resisting systems have drawn attention due to their potentials to solve the above mentioned issues. On the other hand, shape memory alloys (SMAs) are characterized by unique superelastic behavior, which enables the material to recover its original shape after experiencing large deformations. The goal of this study is to assess BRBs whose ductility are improved by utilizing SMA. Nonlinear time history and incremental dynamic analysis techniques are applied to investigate the behavior of the two frames with different stories (four and eight stories) under different ground motion records. The results showed that utilizing BRB made of hybrid steel and SMA resulted in increasing ductility of the structure and decreasing residual displacements of the structures. KEYWORDS brace, ductility, dynamic pushover, nonlinear time history, self-centering, SMA | INTRODUCTIONThere are a plenty of seismic resistant members that have been developed to reduce the likelihood of collapse of structures subjected to earthquake such as braces, [1][2][3][4][5] shear wall, [6,7] confined reinforced concrete structures, [8] filled with high-performance concrete, [9] concrete-filled-steel tube structures, [10] and so on. These days, buckling-restrained braced frames (BRBs) have increasingly been employed as seismic load-resisting systems in the area with high seismic hazard due to the fact that their performance is much better than that of conventional braced frames.Despite the fact that the global geometric configuration of a BRB is very similar to a conventional braced frame, however, the members and behavior of BRB is clearly different from those of conventional braced frames. The key difference is that BRB systems do not buckle. [5,[11][12][13] Conventional braced frames have shown a poor performance in several recent ground motions because of limited ductility, insufficient energy dissipation capacity, and large residual deformations. [14] It is affirmed that BRBs made of steel efficiently resulted in providing structures with significant ductility, stable hysteretic behavior, and large energy dissipation capacity. [15] However, past studies have shown that steel BRBs commonly are brittle and undergo a large residual deformation after earthquakes. [16] The appearance of large residual deformations caused by strong earthquakes makes the residents of building insecure and may even demolish the building. On the other hand, repairing the residual deformations can be expensive and even impossible. [17] In recent years, researchers have attempted to utilize self-centering BRB systems containing SMA material to improve its ductility characteristics and decreasing residual deformations in structures. [18][19][20][21][22][2...

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