Dynamic Behaviors Study On Semi-Rigid Steel-Concrete Composite Frame

In the structural design of composite frames, one of the basic assumptions is that the connections between columns and beams are either perfectly rigid or perfectly hinged. Based on the fundamental assumptions, the analysis and design of structures are simplified and reduced. However, in actual structures, typical connections do not behave in either a perfectly rigid or a perfectly hinged manner and the connections have been proved to be semi-rigid practically. Therefore, the assumptions are unsuitable for reality. It is generally believed that the welded rigid beam-column connections have better behavior and the connection modes have been applied extensively in practice. However, a large number of welded beam-to-column connections of steel moment frames were heavily damaged in the 1994 USA Northridge Earthquake and the 1995 Japan Hyogoken-Nanbu Earthquake. Based on the experimental investigations of Beam-column joints behavior under loading testing, it is found that the semi-rigid connections are of flexible behavior. Comparing with the steel frame structure, the composite frame is more rigid and steady and its ductility and energy dissipation capacity are improved. In addition, for the composite frame structure with the semi-rigid connections, the damping and natural period may be increased and the amplitude is deduced. Thus, the composite frame structure with the semi-rigid connections has better earthquake-resistant capacity. Because the investigations of the dynamic behavior of the composite frame structures with the semi-rigid connections are not enough, the knowledge of the mechanics behavior and the failure mechanism is limited. Therefore, in order to avoid and reduce the earthquake damages, the dynamic behaviors of the composite frame structures with the semi-rigid connections are analyzed and some helpful conclusions and measures for the seismic design are proposed, which will be of considerable theoretical meaning and present reference for engineering design. On the basis of the finite element model of the composite frame structures with the semi-rigid connections established in this paper, the structural natural parameters such as the mode and natural period of structure are further analyzed. Furthermore, the analysis of the structural dynamic behaviors such as the harmonic responses analysis and the time-history analysis are discussed in this paper. The research on the behavior of the composite frame structures with the semi-rigid connections is one of the key projects in the field of engineering and shows an excellent promising in civil engineering. The analysis and studies in this paper provide the basis for constituting code, engineering designing and seismic researches.