| The concrete-filled steel tubular column has a history of more than 100 years.It has higher bearing capacity and better ductility than the plain concrete column.At the same time,its application makes the construction process simple and convenient.The steel pipe can be used as a template that eliminates the process of supporting and demoulding.In recent years,concrete-filled steel tubular columns have been widely used in structures such as high-rise buildings and bridges to withstand large loads.However,when the load is particularly large,the required size of the column is large,and the large-diameter,thick-walled steel pipe required for supply is not enough.The CFRP-constrained concrete-filled steel tubular column is bonded with CFRP cloth on the basis of the concrete-filled steel tubular column.The bonded CFRP cloth can not only enhance the restraining effect,reduce the thickness of the steel pipe,delay the buckling of the steel,but also play the role of anti-corrosion.The combined structure combines the advantages of a concrete filled steel tube column and a FRP confined concrete column.In the actual stress process,the column is usually affected by both the bending moment and the axial force.The force condition can be equivalent to an eccentric axial force.This paper combines theoretical analysis with finite element test to study the mechanical properties of CFRP-confined concrete filled steel columns under eccentric compression.The main work is as follows:(1)In order to study the eccentric compression behavior of CFRP-confined concrete-filled steel tubular columns,firstly,the finite element model is established by using ABAQUS,and the failure mode,load-displacement curve and ultimate bearing capacity of the simulation results are compared with the previous test results.which fully demonstrates that the model constructed in this paper can reflect the mechanical properties of the composite column.(2)In order to analyze the influence of steel tube constrained effect coefficient,slenderness ratio,eccentricity,CFRP restraint effect coefficient and concrete strength on the mechanical properties of the members,39 sets of CFRP-confined concrete-filled steel eccentric compression columns were designed,and the working mechanism was analyzed.The results show that CFRP restricts the plastic flow of the steel pipe,delays the development of the plastic zone of the section,increases the stiffness of the component,and improves the bearing capacity of the component.During the eccentric stress,the stress distribution of the section is always uniform,the tightening force is also non-uniform.As the eccentricityincreases,the plastic deformation of the compression zone decreases,and the bearing capacity of the component decreases.(3)Deeply theoretical analysis of the working mechanism of the component is conducted.because the hoop force of the dangerous section is not uniform,the concept and calculation method of the equivalent tightening force are proposed.The calculation theory of axial compression and bias bearing capacity of concrete-filled steel tubular columns is introduced.Based on the basic theory of concrete-filled steel tubular columns,the calculation method of CFRP-confined concrete-filled steel tubular columns is proposed.When the length is relatively large,the failure of the member occurs before the plastic hinge is formed.In this paper,the safety factor method is used to determine the ultimate bearing capacity of the column,and the eccentricity reduction factor is regressed.The calculation expression of the eccentric compression bearing capacity of CFRP-confined concrete-filled steel tubular columns is obtained.The calculated values are compared with the experimental values,and the accuracy of the formula was verified. |
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