| Steel structures are always considered as the most reliable aseismatic constructions for their good ductility, plasticity and tenacity. 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, non-rigid connections have an excellent energy dissipating mechanism, which can provide more capacity for yielding and ductility. In the meantime, non-rigid connections can save the amount of steel. So the economical and reliable effect is better. Top and seat angles with double web angles connections belong to non-rigid connections. 3-D elastic-plastic finite element analyses are conducted with the general-purpose programming package of ANSYS9.0. in which applied cyclic load to simulate seismic load.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) and bolt pretension forces for first time.Comparing top and seat angles with double web angles connections with full welding rigid connection, elastic-plastic finite element analyses are conducted between monotonic load and cyclic load to obtain the effection on steel frame, which possesses an important referrence value to recognizing the properties of its bearing loads and designing of the structure in the future.The results described above indicate that top and seat angles with double web angles connections have excellent ductility, no significant difference on displacement at the end of beam and also have more capacity of energy dissipating but poor in vertical bearing capacity 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. Because of speciality of semi-rigid connection, the regional stiffness is decreased. So suggestions are given that relation of material characteristic should be controlled among angle steel and high-strength bolt. Designing should be pay enough attention for vertical bearing capacity is decreased afterusing semi-rigid connection.The deep analysis and research are conducted about the behavior and failure mechanism of Top and seat angles with double web angles connections and rigid joint 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. |
