Study On Dynamic Performance Of Semi-Rigid Steel Frame

It is difficult to analyze the beam-column connection of steel frame. In the practical design, it is usually assumed that the connections between columns and beams are either completely rigid or hinged. Such an idealized concept can simplify the procedure of analysis and design, but cannot precisely reflect the actual structure. As a matter of fact, the performance of beam-column connections is between the two mentioned above, namely neither completely rigid nor ideal hinged. The connections have been proved to be semi-rigid. Therefore, the importance of the connections will be magnified if they are regarded as completely rigid, whereas the idealized hinge will neglect the confining function of the connections. In addition, the research on the massive related structures in earthquakes indicate that steel frame with completely-welding joints are so brittle that they tend to break due to their poor node ductility and great residual stress. On the other hand, the semi-rigid connections of steel frame, which is fairly flexible and capable of energy-dissipating, can resist certain seismic load. Consequently, the semi-rigid connection has the ineligible influence on the steel frame's mechanic performance. Therefore, the effects of semi-rigid connections on structural mechanics performance should be taken into account in the analysis and design of steel frame. However, this problem has not been satisfactorily resolved yet.At the beginning, this thesis briefly introduces the present findings of semi-rigid connections, the calculation content and method of design of beam-column connections in the codes from China and other countries, the types of beam-column connections, as well as the characters about semi-rigid connections and the simulated method of the M-θr relation curve of semi-rigid connections. Secondly, with the help of the large general finite element analysis software, it establishes the finite element model of the semi-rigid steel frame, and analyzes the mode and natural period of the semi-rigid steel frame in a profound and systematical way. Furthermore, the analysis of the structural dynamic performances in such aspects as the harmonic responses and the time-history are discussed in this paper. The results show that if the semi-rigid steel frame is considered as completely rigid for seismic design, it may result in greater errors. We should consider the influence of the connection flexibility on the structural dynamic performance in the seismic design of steel frames. Compared with the rigid steel frames, the semi-rigid steel frames have good ductility and energy dissipating capacity. The framework can enhance the stiffness and stability, reduce the seismic load's effects on the steel frame bottom, and then improve the antiseismic performance of the structure. Finally, a new classification standard for the node stiffness is proposed by parameter analysis in this paper. The research achievement may provide reference for the design and the research of the semi-rigid steel frame.