An Investigation on Steel Knee Braced Frames for Lateral Loads

Hysteretic dampers as the most practical passive control methods have improved the seismic performance of steel structures through energy dissipation induced by large inelastic deformations. Among them in this paper, KBF (Knee Braced Frames), a special form of braced frames having a diagonal brace connected to a knee element instead of beam-column joint, is investigated. In such systems, the knee element designed to have inelastic behavior for dissipating seismic energy caused by strong earthquake. In this article, analytical investigation on cyclic performance of knee braced single span one-story frame specimens are described. Nonlinear finite element method have been used for analysis of KBFs. Results have shown good behavior of knee member before its failure and also indicated a number of important considerations for seismic design of KBFs. Moreover hysteretic behavior have shown no pinching effects. At last, a mathematical model has been derived to predict the bilinear behavior of the KBFs and compared with monotonic pushover analysis. Acceptable conformity between mathematical and numerical model proved the accuracy of the proposed model.