Research And Application On The Mechanical Properties Of Concrete-filled Circular Steel Tubes With Latticed Steel Angles Inside

This paper investigated a new type of concrete-filled steel tubes:concrete-filled circular steel tubes with latticed steel angles inside,compared with CFSTs with the other forms of stiffener,this type of components can be easily constructed and located,and usually have better mechanical properties.This paper mainly investigated the mechanical properties of concrete-filled circular steel tubes with latticed steel angles inside under axial tension,eccentric tension,bending,axial compression and eccentric compression.The main contents of the research work include the following aspects:1)The axial tensile properties of specimen were investigated based on the axial tension test,on the basis of test,finite element simulation was applied to analyze the influence of main parameters such as component length,steel ratio and angle steel area etc.on the ultimate tensile strength of specimen.Research results showed that the essential factor that influence the ultimate tensile strength of the axial tensile specimen is the friction force between concrete and the inner steel angles.Based on the results of parameteric analysis,the calculation formula for the ultimate axial tensile stength was established and compared with the computing results of foreign and domestic specification.2)The eccentric tensile properties of specimen were investigated based on the eccentric tension test,on the basis of test,finite element simulation was applied to analyze the influence of main parameters such as component length,steel ratio,angle steel area and eccentric distance etc.on the ultimate tensile strength of specimen.Research results showed that the dominant factor that influence the ultimate tensile strength of the eccentric tensile specimen is the eccentric distance.Based on the results of parameteric analysis,the calculation formula for the eccentric tensile stength was established and compared with the computing results of domestic specification.3)The bending properties of specimen were investigated based on the four-points bending test,on the basis of test,finite element simulation was appliced to analyze the influence of main parameters such as steel-bone ratio,confinement factor,relative distance of steel angles etc.on the ultimate bending strength of specimen,the limit equilibrium method was used to analyze the flexural capacity of specimen.Research results showed that steel-bone ratio and confinement factor have a significant impact on the ultimate bending strength of the bending specimen,while the relative distance of steel angles has a moderate influence on the ultimate bending strength;the existence of the inner steel angles not only improved the ultimate bending strength and bengding stiffness,but also improved the ability of resisting local buckling and the overall mechanical properties.At last,the calculation formula for the ultimate bending stength was established based on the results of parameteric analysis.4)The compressive properties of specimen were investigated based on the axial and eccentric compress test,on the basis of test,finite element simulation was applied to analyze the influence of main parameters such as eccentric distance,slenderness ratio and steel-bone ratio etc.on the ultimate eccentric compress strength of specimen,the limit equilibrium method was used to analyze the eccentric compress capacity of specimen.Research results showed that steel-bone ratio has a significant impact on the ultimate strength of specimen under axial and eccentric compress,when the eccentric distance of the component become larger,the influence of steel-bone ratio on the ultimate compress strength became weaker.At last,the calculation formulas for the ultimate compress strength were established based on the results of parameteric analysis and the research achievement of predecessors.