Improving the CBF brace's behavior using I-shaped dampers, numerical and experimental study

Abstract

Although Concentrically Braced Frame (CBF) is a system with high lateral stiffness, buckling under compressive forces has made it a system with weakness in ductility and not appropriate enough for high seismic zones. Many researchers put a lot of effort into improving the performance of this system by using different methods. Using metallic dampers is also an approach to enhance the performance and ductility of these structures. In this study, a new metallic damper (includes two shear panels that act as an I-shaped shear link), which can be simply constructed, employed in CBF, and replaced after severe earthquakes, is investigated. The I-shaped shear damper and the elements outside of the damper were designed according to AISC 341-16 provisions. Additionally, since the proposed damper is like an I-shaped link, a parametric study was performed using ANSYS finite element software to evaluate the AISC criteria for designing I-shaped links. The results showed that suggestions by AISC to calculate the ultimate strength, overstrength, and stiffness of I-shaped links cannot project the behavior of the I-shaped shear links with high accuracy. Also, this study confirmed that both web and flanges have an ignorable effect on the stiffness in the nonlinear zone and contribute to carrying applied shear forces. Accordingly, a new relation with higher precision was suggested to predict the overstrength of CBFs including the I-shaped shear damper. Moreover, the numerical analyses depicted that the shear damper could behave as a ductile fuse in the structure and maintain other elements in the elastic range.