| Cellular beam is widely used in large span steel structure and steel frame structure of multiple and high rise buildings.It has many advantages,such as saving steel,light weight,nice appearance. It can go through the pipeline by its own hole,which lowers the storey height effectively and has a good comprehensive economic benefit.The beam-column joints of steel structure often take rigid connection. The methods include all-welded connection and bolting and welding mixed connection. Rigid joints have high strength and stiffness and good mechanical performance. However, if the joints are badly welded or the design is unreasonable, the joints may have weld failure and brittle failure under earthquakes, resulting in structural failure or collapse.In steel frame structure of cellular beam, the section is weakened due to the hole in the web. Therefore, the mechanical performance is changed. When the first hole at beam-end has proper position, the plastic sensitive areas will be transferred to the cellular holes. This improves the ductility of joints at beam-end and reduces the possibility of brittle failure at the weld. In the design of multiple and high-rise building structure, the concrete slab forms cellular composite beam when connected to cellular beam by shear connector. The slab composite effect has great influence on the bearing capacity, especially the seismic performance of beam-column joints of cellular beam. There are many research results and corresponding design criteria about the seismic performance of beam-column joints composited by ordinary steel and concrete, while the research on beam-column joints composited by cellular beam and concrete slab is rare. This limits the application of steel frame structure of cellular beam.By taking quasi-static experimental research and theoretical analysis and finite element simulation analysis of beam-column joints of cellular composite beam, we research the damage mechanism of beam-column joints of cellular composite beam under earthquake action, composite effect of concrete slab, factors influencing their seismic performance. The main contents include:By taking quasi-static test of beam-column joints of 2 hexagon-hole cellular beams,2 hexagon-hole cellular composite beams and 1 solid web steel beam, we observe and compare the damage form of the joints research on the damage mechanism of the joints. On this basis, we carry on finite element analysis, research on the influence of parameter variation to seismic performance of beam-column joints of cellular beam and cellular composite beam, including ductility, energy absorption and dissipation performance, stiffness degradation, strength degradation and plastic deformation. We analyze the influence to the seismic performance of joints at different opening rates and different opening margins, and the influence of slab composite effect to the seismic performance of beam-column joints of cellular composite beam. The research result shows that with the increase of opening rate, the bearing capacity of beam-column joints of cellular beam and cellular composite beam reduces and the ductility and energy dissipation capacity lower at different extent; slab composite effect improves the bearing capacity, ductility and energy dissipation of joints. Meanwhile, the web hole can move the plastic hinge at beam-end outward, reducing the possibility of brittle failure at the weld.The above research results lay a good foundation for seismic design and engineering application of beam-column joints of cellular composite beam. |
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