Study On Axial Compression Behavior And Confinement Mechanism Of Steel Tubular-corrugated Steel Plate Concrete Columns

Concrete-filled steel tube columns(CFST)have been widely used at home and abroad because of their excellent mechanical performance,convenient construction,and other characteristics.However,the steel tube is prone to local buckling under the action of compression,which will lead to the confinement effect of the steel tube on the concrete being reduced and unable to give full play to the combined properties of the material.To solve this problem,a new type of steel tubular-corrugated steel plate concrete column is proposed in this paper.The special corrugation form of corrugated steel plate can increase the bite effect between concrete and reduce the calculated length outside the plane,and effectively prevent the occurrence of local buckling.Meanwhile,corrugated steel plate is basically unable to bear longitudinal loads,and would provide a stronger confinement effect on concrete than steel tubes.In this paper,an in-depth study is carried out on the axial compression performance and confinement mechanism of steel tubular-corrugated steel sheet concrete columns.The main research contents are as follows:(1)14 steel tubular-corrugated steel plate concrete columns and 1 CFST column were designed and carried out axial compression tests with the research parameters of the section width,corrugated steel plate thickness,steel tubular width,corrugated steel plate wave height,and whether the concrete in the steel pipe is poured.The failure mode,the load-strain curve of specimens,and the load-strain curve of the corrugated steel plate and steel pipe were observed by experiments,and the strain distribution of the corrugated steel plate was discussed.The test results showed that the axial compressive behavior of steel tubular-corrugated steel plate concrete columns is better than those of CFST columns with similar steel content.The development speed of transverse strain at different positions of corrugated steel plate is different,and the crest is larger than the middle and far larger than the trough,which indicates that the wave of corrugated steel plate has the greatest confinement effect on the concrete.(2)Based on the load-strain curve of the corrugated steel plate and the stress-strain relationship of steel,the load-stress curve of the corrugated steel plate is derived.The phenomenon of different constraints at different positions of corrugated steel plate is analyzed.Based on the principle of the equal area of materials and the principle of force balance,the relationship between the average transverse stress of corrugated steel plate and the equivalent constraint stress of core concrete is obtained.The influences of parameters such as section size,wave height,diameter-to-width ratio,and thickness of corrugated steel plate on the lifting coefficient and ductility of core concrete are explored by the means of peel analysis.(3)The finite element model of the steel tubular-corrugated steel plate concrete column was established,and the compression constitutive relation of the core concrete was modified.The accuracy of the model and the modified constitutive relation were verified based on the test results.To further explore the stress mechanism of the S-CSC column,the stress distribution of corrugated steel plate and concrete is analyzed in detail.Meanwhile,the influences of concrete strength,diameter-to-width ratio,yield strength of corrugated steel plate,thickness of corrugated steel plate,yield strength of steel tubular,and the thickness of steel tubular on the axial compression behavior of the S-CSC column are also compared through parameter analysis.(4)Combined with a large number of parameter analysis results,the influence of material strength and section size on the equivalent confinement stress of core concrete is explored,and the expression of the equivalent confinement stress is derived.Finally,based on the superposition principle and the calculation method of compressive strength of confined concrete proposed by Mander,and considering the influence of slenderness ratio on the bearing capacity of composite columns,a formula for calculating the bearing capacity of steel tubular-corrugated steel plate concrete column was proposed.The calculation results of the formula fitted well with the experimental results and the finite element simulation results.