| The traditional beam-column joint connection methods suffer from issues such as high on-site labor intensity,low production efficiency,and difficulty in ensuring construction quality.The production mode of high efficiency and low energy consumption embodied by fabricated steel structures has become the top priority in the development of green buildings.Circular steel tube concrete column has been widely used for its high bearing capacity,superior seismic performance and small section.The surface of the circular steel tube column is not straight and has a closed section,which limits its assembled connection with the endplate of the H-shaped steel beam.In response to the above issues,a fabricated concrete-filled circular steel tubular column-steel beam endplate joint was proposed.The seismic performance of the proposed new type of the joints under low cycle reciprocating loads was studied,and the research content is as follows:（1）A fabricated concrete-filled circular steel tubular column-steel beam endplate joint was proposed and designed,and a corresponding finite element model was established on this basis.The feasibility of the finite element method was confirmed through relevant experimental tests.（2）The seismic performance of fabricated joints with different structures was studied,and the short beam endplate joints with ring plate can meet the seismic requirements of"strong joints,weak components";The energy dissipation coefficient of short beam endplate connection joins with ring plate has increased by 59.3%,14.5%,and 13.4%compared to U-shaped connection joints,U-shaped connection joints with ring plate,and short beam endplate connection joints,respectively.This indicates that the seismic performance of short beam endplate connection joints with ring plate is good.（3）Using the short beam endplate connection joint with ring plate as the specimen BASIC,parameter analysis was conducted on its seismic performance.The results indicated that if the beam endplate and short beam endplate are too thin,local deformation may occur.It is recommended that the thickness of the beam endplate be greater than 16mm（0.80d0）,the thickness of the short beam endplate be greater than 12mm（0.60d0）,and d0 is the bolt diameter;Thin short beam endplate stiffeners were prone to local yielding.It is recommended that the thickness of the short beam endplate stiffener be greater than 10mm（0.71t2）,where t2 is the thickness of the short beam endplate;When the position of the outer ring plate was low,the strengthening effect of the ring plate on the joint domain was insufficient.It is recommended that the outer ring plate be flush with the upper edge of the stiffener of the short beam endplate;The second-order effect caused by axial load increases with the increase of the axial load ratio.The axial load ratio increased from 0.3 to 0.8,and the displacement ductility coefficient decreases by 31.5%.It is recommended that the axial load ratio not exceed 0.7;When the beam-to-column linear stiffness ratio reached 0.59,the joint domain was prone to failure.The beam-to-column linear stiffness ratio increased from0.18 to 0.59,and the ductility of the corner decreased by 26.1%.When the diameter and thickness of circular steel tube columns are relatively large,they do not meet the seismic design criteria of"strong nodes,weak components".It is recommended that the beam-to-column linear stiffness ratio line be less than 0.59,and the diameter to thickness ratio of the circular steel tube column should not be greater than 43.8.（4）A bearing capacity calculation formula suitable for each parameter value has been established,and the error between the results and the finite element results is within 8%;A restoring force model for the fabricated concrete-filled circular steel tubular column-steel beam endplate joint has been established,which serves as a reference for elastic-plastic seismic time history analysis of the fabricated concrete-filled circular steel tubular column-steel beam endplate joint. |
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