Study Of The Compressive Properties Of Multi Cavity T-Shaped Concrete-Filled Steel Tubular Columns

When the special-shaped concrete-filled steel tubular column is reasonably used in buildings,the excessive size of the column cross-section can be effectively avoided and the utilization ratio of the indoor space can be increased by solving the column edge protrusion at the wall corner.In recent years,researchers have proposed various kinds of special-shaped concrete-filled steel tubular columns with different cross-sections,but their mechanical properties need to be further studied.To investigate the mechanical properties of a new type of multicavity T-shaped concrete-filled steel tubular column,experimental studies on its axial compression behavior and eccentric compression behavior are conducted,along with the parameter analysis using the finite element method.Firstly,the experimental study on the axial compression performance of the multicavity T-shaped concrete-filled steel tubular column was performed,the test variables of which included the steel tube wall thickness,concrete strength,and slenderness ratio.Moreover,two ordinary T-shaped concrete-filled steel tubular columns were designed for comparison.The results showed that both the multicavity and ordinary T-shape specimens exhibit local drum failure modes,and the position of drum shows no regularity.The ultimate bearing capacity of the multicavity T-shaped specimens is significantly increased with the increase of concrete strength or steel tube wall thickness.In addition,the load-longitudinal average strain curve of the specimen with high concrete strength decreases sharply when the specimen reaches the ultimate bearing capacity.Note that the specimen with large wall thickness shows strong deformation ability.When the vertical displacement is loaded to a large value,the weld joint cracks at large drum curvatures,but the load-longitudinal average strain curve of the specimen still has no obvious drop phase.The reason for weld cracking is not that the weld quality is not reliable,but that the drum bending degree is too severe.Therefore,it is suggested that when high strength concrete is adopted,steel tubes with large wall thickness should be used to give full play to the performance of these two materials.When the slenderness ratio varies from 4.51 to 11.27,the ultimate bearing capacity of the specimen decreases with the increasing slenderness ratio,but the reduction is insignificant.Compared with the ordinary T-shaped specimens,the ultimate bearing capacity and deformation capacity of the multicavity T-shaped specimens show obvious advantages.Within the scope of the research parameters in this paper,it is recommended to use Eurocode 4 to calculate the axial compressive bearing capacity of multicavity T-shaped concrete-filled steel tubular column.Secondly,the experimental study on the eccentric compression performance of the multicavity T-shaped concrete-filled steel tubular column was conducted,the test variables of which included the eccentric distance and slenderness ratio.Also,an ordinary T-shaped concrete-filled steel tubular column was designed for comparison.The results showed that all specimens are in the bending failure mode,and the lateral deflection of these specimens is basically symmetrical from up and down,consistent with the half sine wave curve.In addition,the ultimate bearing capacity of the multicavity T-shaped specimens decreases with the increasing eccentric distance and slenderness ratio.When the slenderness ratio varies from 4.51 to 11.27,the reduction of ultimate bearing capacity of the specimen is insignificant.Compared with the ordinary T-shaped specimens,the ultimate bearing capacity and deformation capacity of the multicavity T-shaped specimens show obvious advantages.Finally,numerical simulation was carried out by using the nonlinear finite element software ABAQUS,and the rationality of the model was verified by the existing test results.Afterwards,parameter analyses were performed.The analysis results showed that compared with the multicavity T-shaped specimens,the contact pressure between the steel tube and concrete is mainly concentrated in the internal corner of the ordinary T-shaped specimens,which does not exert effective restrain on the concrete but accelerates the damage of concrete.In addition,the initial stiffness and deformation capacity of the multicavity T-shaped specimens have no obvious change with the increasing steel strength.When the strength grade of the steel tube is low or the wall thickness is small,the influence of slenderness ratio on the ultimate bearing capacity of the specimen under axial compression is more significant.When the slenderness ratio increases from 4.65 to 38.73,the axial compression stability coefficient of the multi-cavity T-shaped concrete-filled steel tubular column decreases from 1.0 to 0.74.When the eccentric distance of the specimen is less than 60 mm,the ultimate bearing capacity of the multicavity T-shaped specimens decreases with the increasing eccentric distance,and it reduces by 9.95%on average for every 10 mm increase in the eccentric distance.