Study On The Dynamic Properties Of The Megaframe-Tube Structure

Based on the finite element theories, this thesis does a systematical research on the megaframe-tube structure, and the global objective is the assessment of the seismic usefulness of this kind of structure.Firstly, conceptual analysis was carried out on the megaframe-tube structure, and its model for finite element analysis was identified. Compared with the traditional frame-tube structure, modal analysis was conducted on the model to evaluate its natural vibration properties of global structure. Then, spectrum method and dynamic time history analysis was performed to assess the dynamic properties of the megaframe-tube structure under slight earthquake. Considered the nonlinear factors of the structure, elasto-plastic seismic behavior in rare seism was studied in this thesis. Finally, design parameters which influence the mechanical properties of the structure were analyzed.The conclusion of this paper is reached:1. The dynamic properties for the megaframe-tube and the traditional frame-tube under slight earthquake are similar. There is a decrease tendency in the interstory drift figures where megabeams are set. The figures of floor shear force and floor moment are similar to those of the frame-tube structure. The ratio of the seismic force of the megacolumns is larger than that of the columns of the frame-tube structure.2. Under rare seism, there is also a decrease tendency in the interstory drift figure where megabeams are set, but totally, the collapse of the structure can be prevented in the severe earthquake. Under the 7 intensity scale earthquake, there is no plastic hinges appeared in the megacolumns, and few plastic hingesappeared in the secondary frame. In the regions which earthquake intensity scale is 7, for megaframe-tube structure, the structure could be able to (a) resist minor earthquake without damage, (b) resist moderate earthquakes without structural damage, but with some non-structural damage, (c) resist major earthquakes of severity equal to the strongest that could be experienced in the area, without collapse but with some structural as well as non-structural damage.3. Converting the sections of megacolumns, megabeams, secondary frames and tubes can influence the top floor displacement, velocity, acceleration and base seismic force. Enlarging the sections of megabeams, secondary frames and tubes can control the maximum interstory drift. Converting the measurements of megacolumns and tubes can adjust the propagation of the seismic force and reduce the plastic hinges of the outer frames.