The Mechanical Properties Influence Of Local Empty Drum On Concrete-filled Rectangular Steel Tube Beam Column Joint

In the 1960 s,concrete-filled steel tube(CFST)structures were introduced into China because of their excellent seismic performance.Then through the joint efforts and research of experts from all walks of life in the past twenty years,concrete-filled steel tube structure in China has entered the period of High Speed Development.During this period,the form of concrete-filled steel tube structures has also been fully developed.From the beginning of the circular concrete-filled steel tube structure to the square,rectangular concrete-filled steel tube structure has also made great progress.Inner diaphragm joint is a classical form of concrete-filled steel tube joint.There are two internal partitions with filling holes inside the joints,which are welded to the column.The steel beam is also connected to the column by welding.Because of its simple structure,safety and reliability,It is recommended as the main beam column connection node in the technical specification for rectangular concrete-filled steel tube structure(CECS159:2004).However,due to the uneven level of construction teams in China,various construction problems are unavoidable in the project.The Ninth Design and Research Institute of Mechanical Industry Co.,Ltd.(Changchun)believes that the phenomenon of empty drum under the diaphragm may affect the mechanical properties of the joints and Jilin Construction University was commissioned to study the influence of hollow drum on the performance of rectangular steel tubular concrete and section steel joints.According to the actual project of the Ninth Design and Research Institute of Mechanical Industry,we designed the 1:2 model specimen of rectangular concrete-filled steel tubular column-H steel beam with empty drum below the inner partition and carried out the experimental study of low cycle reciprocating load.The results show that the inner spacer joints with empty drum still have good seismic performance.With the increase of the ratio of empty drum,the ultimate bearing capacity of the specimen decreases slightly.But ductility and energy dissipation improved slightly.We have carried out low-cycle load test on 3 concrete-filled steel tubularcolumns with inner diaphragm with empty drum-H-type steel beam girder joints.The results show that: The Inner diaphragm joints with empty drum still have good seismic performance.With the increase of the ratio of empty drum,the ultimate bearing capacity of the specimen decreases slightly,but the ductility and energy dissipation performance improved slightly.The finite element analysis software ABAQUS is used to simulate and analyze the edge span joints of concrete filled steel tubular columns with inner diaphragm with hollow drum,and the results are compared with the experimental results.The results show that the failure patterns,skeleton curves and hysteretic curves of the simulated analysis are in good agreement with the experimental results.It is also proved that the definition of interaction and the setting of constitutive relation in simulation analysis are reasonable.On this basis,the effects of the ratio of empty drum,the position of hollow drum,the thickness of steel tube wall,the ratio of axial compression and the thickness of inner partition plate on the bearing capacity and seismic performance of the side span joint of concrete filled steel tubular column(CFST)column with hollow drum are studied.A concrete conclusion is drawn.