PASSIVE CONTROL OF STEEL BRACED FRAMES USING DUCTILE KNEE ELEMENTS

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 Frame), a special form of braced frame 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 stro ng earthquakes. In this paper, first, experimental investigation of cyclic performance of a knee braced single span one-story frame specimen is described and experimental results are verified through non-linear finite element analysis procedure. The test 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, a mathematical model has been derived to predict the bilinear behavior of the KBFs. Acceptable conformity between mathematical and numerical model proved the accuracy of the proposed model.