| Steel structures are always considered as the most reliable aseimatic constructions for their good ductility, plasticity and malleablility. However, brittle fracture occurred successively in steel frames in the 1994 Northridge Earthquake and the 1995 Hyogoken-Nanbu Earthquake. The two earthquakes indicate that rigid connections have poor ductility and brittle fracture happens easily. Nevertheless, nonrigid connections have an excellent energy dissipating mechanism, which can provide more capacity for yielding and ductility. In the meantime, nonrigid connections can save the amount of steel. So the economical and reliable effect is better. Steel beam-column double-angle connections belong to nonrigid connections. As a matter of fact, there is almost no domestic connection test on this aspect presently. It is found out that most of reports in point are on strong-axis connections and there are few introductions about weak-axis connections. The actual code for design of steel structures has no specific provisions about them. Considering those above, 3-D elastic-plastic finite element analyses are conducted with the general-purpose programming package of ANSYS6.1. The study of connection is rather comprehensive and systematic. Analyzing models are built which can simulate actual behavior with more precision, synthetically considering nonlinear (material, geometry and contact), bolt pretension forces and column axis forces for fist time. The main scopes of this paper include: ⑴Elastic-plastic finite element analyses are conducted between monotonic load and cyclic load in order to study the similar and the different aspects and reveal organic relationship each other.⑵Elastic-plastic finite element analyses are carried out among species of 7 series under monotonic load in order to discuss the influence of parameters including friction coefficients, bolt pretension forces, column axis forces, welding strength, bolt strength, angle steel strength, bolt grade and so on.The results described above indicate that steel double-angle beam-column connections have excellent ductility and also have more capacity of energy dissipating and better behavior under cyclic load than under monotonic load. In addition, the plastic strain resulted from angle steel and high-strength bolts provide necessary ductility in connections. However, warping deformation happened in column web and angle steel before failure because of deficient stiffness in connections. So suggestions are given that not only relation of material characteristic should be controlled among angle steel, high-strength bolt, and welding, but also stiffness and strength should be enhanced by installing stiffening-rib in connections.The deep analysis and research are conducted about the behavior and failure mechanism of steel double-angle beam-column connections, which provide significant information and reference to develop the theory of steel beam-column connections and their design method, and to explore new forms of connections.
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