Study On The Mechanical Property Of A New Assemble Beam-to-column Two-way Connection

With the continuous development of science and technology in our country, the steel structure has been widely used in the construction field. The steel structure has many advantages as light weight, high stiffness,and it has many characteristics, such as good seismic performance, convenient installation, short construction period, under cyclic loading well etc. Beam-column connection node is the key stress area. The performance of node directly affects the stiffness, strength, security, stability and the project cost in the whole structure. This thesis will focus on the mechanical capacity of the new beam-column assembly type bidirectional connections under monotonic load and under cycle load, understand the mechanism of failure and provide theory reference for the engineering practice.The study of this thesis is a kind of new beam-column assembly connection node with a cantilever beam splice. Cantilever beam and frame beam are connected by upper and lower flange splice plate’s interactive layout. One side of splice plate connectes with steel beam flange by bolting, the other side connects with the steel beam by welding. Cantilever beam and column are completed by welding in the factory. Cantilever beam and frame beam are completed by splicing installation at the construction site. The process of the completion of welding in the factory, rapid installation in place at the construction site has improved the construction efficiency. It reduces the workload of welding, and the operation is convenient.This thesis is based on BASE specimen of a new type of beam-column assembly type bidirectional connection node, designs the four series of specimens by changing the length of the cantilever beam, the number of bolts at flange splice plate, bolt pretension and friction coefficient and other parameters. And finite simulation analysis for the series of specimens are made by finite element analysis software ABAQUS.The bearing capacity of series of specimens are studied under monotonic load and under cycle load. The conclusions were drawn as follows:(1)In order to satisfy with the requirements of seismic, strong design method is recommended to design a new type of beam column assembly type bidirectional connection node model.(2)With the increasing of the cantilever beam length, the distance between splice and beam is increasing, and the maximum limit bearing capacity of the series of specimens is slightly reducing. At the same time, plumpness of hysteresis curve is gradually reducing under reversed cyclic load; the area of hysteresis loop is gradually shrinking; the ductility performance is decreasing gradually. In the view of difficult transportation in long cantilever, the length of the cantilever beam section should be reasonable. The reasonable range is 1.1 to 1.5 times the range of beam height, and which should not be more than 1.6m.(3)When the actual number of bolts is 25% less than number calculated according strong design method, the maximum limit bearing capacity of specimen decreases slightly. The maximum limit bearing capacity of specimen remarkably decreases when further reducing the bolts, the bolt shows sliding phenomenon in advance under cycle load, and ductility and energy dissipation of the series of specimens are increased gradually with the reduction of the number of bolts. Increasing number of bolts has no significant effect on improving the maximum limit bearing capacity of specimen, but that makes ductility and energy dissipation of the series of specimens’ reduction. Therefore, for the actual engineering design, in the premise of meeting the economy, in order to ensure that all series of specimens also has a good seismic performance and bearing capacity at the same time, it is not necessary to increase the number of flange splice bolt too much.(4)When the actual bolt pretension is within the scope of the specification specified value plus or minus 20%, the maximum limit bearing capacity of specimen don’t appear to be much different. However, pretension of bolt is increaseing, which makes the intensity of the splicing increased. When bolt of spices is under cycle load, the load is increasing during sliding time. The ductility and energy dissipation of the series of specimens are decreasing gradually with the increasing of the bolt pretension.(5)Due to the equivalent strength when designing the specimens, the increased friction coefficient makes the maximum limit bearing capacity of the series of specimens increase a little. However, the ductility and energy dissipation of the series of specimens are decreased gradually with the increasing of the friction coefficient. This is mainly because high strength bolt expend seismic energy by the friction of bolt nut or extrusion between screw and screw hole while the increased friction coefficient let the bolt under the load sliding and extruding decrease.(6)When two sides steel beam and steel column of two-way beam column connection repectively adopts flange connection and web connection, there are different initial stiffness in two directions of beam column joints, the mechanical properties of strong axis connection and weak axil connection under monotonic loading and cyclic loading put up not exact match.