Seismic Performance Evaluation of Knee and EBF Braced Frames Using Nonlinear Static Analysis

Abstract

Earthquake-resistant structure systems should be designed to stand large deformation to absorb and attenuate imposed energy due to an earthquake while providing sufficient stiffness to transfer the forces to the base without collapse. Knee Braced Frames (KBF), which involves added additional diagonal elements to a frame to increase its ability to withstand lateral loads, is suggested by several researches. In this study, the seismic performance of KBFs are evaluated and compared with Eccentric Braced Frames (EBF). Nonlinear static analyses were utilized for seismic evaluation and comparison between the mentioned frame systems. Three steel structures of 5, 10, and 15-story were numerically modeled, and the seismic parameters such as lateral stiffness, inter-story drift, ductility, and response modification factors were calculated for each structure system. It was observed that using KBF systems resulted in a reduction in intersotry drifts compared to EBFs. KBF systems show more stiff responses in comparison with EBFs and they presented much more stiff response by reducing the knee element length. The KBFs have more ductile behavior in comparison with EBFs, although base shear in KBFs is less than EBFs.