Theoretical Analysis And Experimental Study On Semi-rigid Connections Of Steel Structure

In order to resist the structure's lateral load and reduce the lateral displacement efficiently in the tier or tall building structures, it is generally designed the joint as rigid joint in the past decades. It had been believed that the welded rigid beam-column connections would have better behavior and the connection modes had 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 Earthquakes, which have arousing widespread interests of academic and engineering circles. But semi-rigid connections, which is formed by high strength bolts and connecting components, for example angle, end-plate and shape T steel, have an excellent energy dissipating mechanism to resist earthquake loads and prove more capacity for yielding and ductility, meanwhile, the semi-rigid connections can save steel capacity, and become a kind of economical and reliable connections.Top and Seat angles with double Web Angles Semi-rigid Connection is a typical form of semi-rigid connections with non-linear characteristics. However due to complexity of the destroy and effect factors, few studies on this kind of connections could be found in the literature. This paper is focus on studies of the semi-rigid joints and over-all steel frames by theoretical analysis and experimental performance.The joint is an important component of structures and the seismic performance of the connections have a direct impact on the seismic performance of structures. Study on seismic performance of the joints is the premise of the study of seismic behavior of structures. This paper, first of all, carries out the theoretical and experimental research of the semi-rigid connections. The main work is as follows:1. This article the research background and progress of semi-rigid connections domestic and abroad are summarized. A systematic classification and study stratagem of semi-rigid connections are discussed. Through theoretical study is conducted on Semi-rigid connections with dual-web and top angle as one kind of semi-rigid connection.2. Based on experimental study of semi-rigid connections with dual-web and top angle, finite element numerical simulation and analysis for a node of this type of connections under unidirectional load are performed and the whole process (stress changes, the emergence and development of plastic zone, breakage) of the node is obtained.3. Based of numerical simulation and analysis of semi-rigid connections with dual-web and top angle under unidirectional load, numerical simulation and analysis for 9 nodes of this type of connections with different sizes under cyclic loading are performed. Hysteresis curves and the stiffness degradation curves of the nodes are obtained. The energy performance and ductility of this kind of connections are studied. The corresponding hysteretic model is established initially and the model parameters are determined. Theoretical basis is provided for studying the performance of steel frames with semi-rigid connections under seismic loading.From the results obtained foregoing, we can see that this kind of connections have good seismic performance. According to the performance of semi-rigid connections, the engineering and academic circles began to study semi-rigid connections overall framework of dynamic performance, however the study is still in the start-up phase, the theoretical basis for the relatively mature and experimental basis are not established yet. By referring large number of published articles domestic and abroad, the following works are achieved:1. The main section contingency reaction force, changes in stiffness between layers, framework acceleration response of various layers, each floor displacement reaction, response and basal shear layers hysteresis curve of the overall framework are studied with the pseudodynamic testing technology and the dynamic responses to the earthquake loadings of steel frames with different rigidness are analyzed.2. The rigidness matrix of structures with semi-rigid connections is derived by virtual principle. Rayleigh damping matrix and NEWMARK numerical integration algorithm.are adopted. Corresponding programs are developed with MATLAB. The elastic time-history evolutions of two structures with and without braces are conducted and the results are analyzed.All the results obtained in the present study show that the semi-rigid connections and the semi-rigid steel frame have good seismic performance. Comparing with the full-rigid steel frame structure, though the semi-rigid steel frame is less rigid and steady,its ductility and energy dissipation capacity are improved. In addition, for the semi-rigid steel frame structures, the damping and natural periods maybe increased and the amplitude is deduced. Thus, the semi-rigid steel frame structures have better earthquake-resistant capacity. The steel frames of semi-rigid connection without braces are sensitive to the semi-rigid behaviors, and it is not suitably to use semi-rigid connections with small rotational rigidity in the high-rised steel frames without braces.The research on the behaviors of the semi-rigid connections and the semi-rigid steel frames are one of the key in the field of engineering and shows an excellent promising in civil engineering. The achieved results in this study provide the basis for constituting code, engineering designing and seismic researches.