Experimental And Theoretical Study On Castellated Composite Beam And Compound Spiral Hoop Reinforced Concrete Column Connection

As a new structure form, the composite structure constituted by steel-concrete composite beam(SC beam) and compound spiral hoop reinforced concrete column(CSHRC column) gives full play to the advantages of steel and concrete. The structure form has the advantages of convenient construction and lower cost. The joint of castellated composite beam(CSC beam) and compound spiral hoop reinforced concrete column is the same with SC beam and CSHRC column structure system, which uses conventional steel beam with web opening beam to let pipes of equipment pass, reduce the floor height of buildings and save steel. In order to study the joint’s failure mechanism, seismic behavior, bearing capacity, and the mechanical properties and design methods of castellated composite beam under negative moment, while giving theoretical guidance to structure design and promoting the development of SC beam and CSHRC column structure form, the paper mainly does work as follows:(1)Two 1/2 reduced scale joints of CSC beam-CSHRC column specimens and a simulating core zone specimen were analyzed. And the quasi-static tests under cyclic loading were done to study strength, stiffness, ductility and energy dissipation ability of joints. A classification standard of the joint is proposed according to the curve of dimensionless moment-dimensionless rotation. And based on experimental results and the guidance of current codes, the paper proposes a formula to evaluate the shear capacity of through-beam type CSC beam and CSHRC column joint. The experimental results show high strength, good ductility and energy dissipation ability of the joint. The inter-story drift ductility factors of the joints are 4.55 and 4.30. The rotation ductility factors are 4.66 and 4.60. The equivalent viscous damping coefficients are 0.46 and 0.38. These results indicate high strength and good energy dissipation ability of two joints.(2)The finite element software ANSYS is used to establish a 3D finite element model of CSC beam and CSHRC column joint, and the loading system is the same as experiment, which mixes loading control and displacement control. By comparing the calculated results and the experimental result, the failure mode is identical, and the ultimate bearing capacity shows deviations of 3.58%, 7.1%, while the deviations of maximum rotation angle and stiffness would be less than 7% and 5%, respectively. These results are all in reasonable range, which shows accuracy of ANSYS model.(3)18 3D finite element model were established for parametric analysis. The parameters, such as the height of steel beam, expansion ratio of castellated steel beam, and location of web opening, were taken into consideration for analyzing their mechanical properties. Then according to the finite element analysis results of joints, the formula above has been modified. Meanwhile, the applicability of the modified formula is proved by comparing the experimental values and calculated values of 6 specimens at home and abroad. The results show that the original height and expansion ratio have a great influence to the bearing capacity and stiffness of the joints. And the location of web opening have a great influence to failure mode.