| The concrete-filled flat steel tubular columns with large length width ratio not only have good bearing capacity,but also have small section width,which can be hidden in the wall and solve the problems such as convex angle of indoor columns.They are more and more used in engineering practice.However,due to the small section size of the flat column,it is not suitable to use the joints with diaphragm in the pipe,and it is not suitable to use the exterior diaphragm connection in the residential buildings.Therefore,it is proposed to apply the Vertical Stiffener Joint to the flat steel tube concrete column beam structure.In addition,the connection between the beam and the joint is generally bolted and welded,but through a large number of data analysis,it is shown that the quality of the lower flange weld is difficult to guarantee,and brittle failure is easy to occur under the action of earthquake.To solve this problem,the bolted and welded joint form of the lower flange and the upper flange is proposed.Therefore,this paper has carried out the research on the Bottom Flange Bolted and Top Flange Welded Vertical Stiffener Joint(BWVSJ)of concrete-filled flat steel tube and H-shaped steel beam.The main contents include:(1)This paper completed three full-scale quasi-static tests of cross-shaped joints,and studied the changes in the ultimate bearing capacity of beams and corbels on the joints under positive and negative moments.By analyzing the load-displacement curve of the joint,the stiffness degradation of the standard specimen is slow,the bearing capacity degradation is not obvious,the ductility coefficient(?)is 3.22,and the equivalent viscous damping coefficient is about 0.2,which proves that the joint has good seismic performance.In addition,the transmission force mechanism and failure mode of the node are researched,and it is found that the node structure is reasonable and the transmission force is clear.(2)In order to study the optimal joint structure of the BWVSJ,the finite element model which is well fitted with the test is used to study the extension length of the bracket at the joint,the thickness of the lower flange of the bracket,the ratio of width to thickness of the column and the layout of the bolt.The results show that the ultimate bearing capacity of the beam under the action of positive and negative bending moment tends to be the same with the increase of the extension length of the corbel;the difference between the thickness of the flange plate under the corbel and the thickness of the flange of the beam should be less than 2mm to reduce the amount of steel used and the asymmetry;under the condition of meeting the shear bearing capacity,the influence of the thickness of the column wall on the bearing capacity of the joint is large,and the influence of the column width on the bearing capacity of the joint can be ignored;when calculating the bolt,it is suggested to select a design method with less number of bolts on the premise of meeting the bearing capacity,so as to reduce the cost and field installation workload.(3)Based on the yield line theory and superposition principle,the calculation formula of the bending capacity of the BWVSJ is put forward.The ratio of the formula to the test results under yield and ultimate state is 0.91 and 0.88 respectively.Modify and verify the shear capacity calculation formula of the outer rib ring plate joint,the difference between the formula and the finite element simulation results is about 3.6%.The calculation formulas of "strong column weak beam" and "strong joint weak component" are modified,and the checking calculation formula of yield bearing capacity of the joint core area is given. |
PDF Full Text Request