| In the design of building structures,the design specifications for progressive collapse resistance of steel structures and composite structures have not yet been drafted,so more research is needed to supplement them.In this paper,test research,numerical simulation and theoretical analysis are carried out for the collapse behavior of a differently beam-column connection.The connection contains the beams’ lower flange bolting the through diaphragm and upper flange welding the outer ring.The specific research work and conclusions are as follows:The differently constructed square concrete-filled steel tubular column with H-beam connections and a whole set of equipment were designed and processed.By observing the test phenomenon,analyzing the load-displacement curves and deflection development of specimens,it was concluded that the failure of the specimens mainly passed through the beam bending stage,the tension bending stage and the catenary stage.The strong tie-breaking force through the diaphragm and the bolted connection at the lower flange greatly improve the redundancy of connections,and the components tie more reliable.The two specimens respectively with round holes and slotted holes at the web connecting plate were compared and analyzed.It showed that the slotted holes at the web connecting plate didn’t weaken the test specimen and didn’t reduce the yield bearing capacity at the stage of bending resistance.On the contrary,it significantly improved the ultimate bearing capacity and rotation capacity of the specimen at the catenary stage.At the same time,the strain of each component on the specimens were analyzed.Results showed that the slotted holes at the web connecting plate have no obvious influence on the upper strap plate strain,but the strain on the outer ring plate,the through diaphragm and the web connecting plate is increased.The optimized construction facilitates the play of the material properties of the above three components and places higher requirements on their material properties.A finite element model was established and verified,and a parametric analysis was performed on 31 sets of variable specimens.Results showed that the increase of the lower flange thickness had no significant effect on the ultimate bearing capacity,but it was not conducive to the rotational deformation of the connection.When the width of the lower flange increases,the ultimate load and rotation capacity will promote.Single-row bolts are not conducive to the practical application of the project compared to the double-row.The more dispersed the double-row bolts are,the better the mechanical properties of the test piece are improved.The 4 staggered hole connection at the connection plate has a greater impact on the bearing and rotation capacity of the specimens.The peak load growing rate under the same caliber will decrease as the cut depth increases.Based on the analysis of elastic theory and the relationship of geometry,the load sharing of different resistance mechanisms of the specimen during different processes was obtained.At the same time,the correctness of this calculation method was verified based on the conclusion that the axial tensile force of different sections of the steel beam is the same.By comparing the results between test and theoretical calculation,it’s found that JGJ99-2015 can be used to design and predict the yield capacity of the connection.Meanwhile,through calculation,the surface load limit value of this new-type connection for frame structure analysis is obtained.Divide the area according to the actual floor load distribution,and make assumption that this new-type connection is the rigid connection.Through analysis,it is found that this assumption and calculation method are closer to the actual work. |
PDF Full Text Request