Study On Performance Of Knee Brace Steel Frame Under Low-reversed Cyclic Loading

Knee braced steel frame (KBF) is a new form of energy-consuming support structure which sets a section of knee bracing near the beam-column connection. One side of KBF connects with column and the other end connects with the beam. The main pole connects to the knee bracing that can provide lateral stiffness for the framework. The knee bracing is designed to be energy dissipation components in support system. Under the frequent earthquake, the knee bracing will yield first while the beams, columns and the main pole will always maintain flexibility, which can protect the main structure; Under the rare earthquake, the knee bracing segment will shear yielding earlier through the non-elastic deformation of the knee bracing, so that the structure of the main components are not destroyed. Because the plastic damage is controlled in the secondary component of structure, the restoration of structure can be relative easier.KBF has the advantages of good ductility, rigidity and has overcame the defect of using the main elements of the structure yielding to expense energy. Because the plastic damage can be controlled in the secondary elements of structure and can be repaired easier, the KBF is a effective lateral support structure system, which is suitable for high-intensity earthquake zones.The seismic performance of knee brace steel frame forms is also studied by experiment. The test object is two-story KBF steel frame structure model scaled proportional to 1/3,using MTS electro-hydraulic loading system and control software for the model to simulate the cyclic loading test. Through the experiment, the seismic loads carrying capacity of structure, ductility, deformation, hysteresis curve, stiffness degradation are researched.By finite element analysis software ANSYS, the computer simulation of knee bracing steel frames is conducted, and then uses the beam and shell element combination model to analyze the energy dissipation capacity of the KBF steel frame structure, which has good agreement with the experimental results. Finally, the several forms of knee bracing steel frame model are established and the comparison between energy dissipation capacity and stiffness is conducted.