Research On Axial Compressive Bearing Capacity Of Circle Steel Pipe Columns Bonded By CFRP With Spacing Adhesion

The basic idea of reinforcing steel members with fibre reinforced composites is to locate areas requiring reinforcement.Then,according to the performance characteristics of the fiber material,it is bonded to the surface of the component with special adhesive material.When the adhesive layer solidifies,the fiber material and steel are combined to form a composite material,which enhances the cross-section stiffness and shares a part of the service load,so that the damage does not extend,and meets the service requirements of the structure.In this paper,the reasonable bonding interval range of carbon fiber spaced steel column is studied.Secondly,the revised coefficient of reinforcement bearing capacity is introduced to consider the difference between theoretical reinforcement bearing capacity and numerical simulation bearing capacity,and the relationship curve between the coefficient and the number of sticking layers is drawn.Finally,in the process of establishing the finite element model,it is found that the calculated results are similar to the experimental results when the bonding layer and carbon fiber are combined into a composite material.This paper mainly carries out two tasks:2.The theoretical bearing capacity of CFRP reinforced steel tubular columns is calculated by converting the thickness of CFRP into steel tubular by using converted section method.However,this method does not consider that the interface damage between CFRP and steel in actual reinforcement will affect the bearing capacity of CFRP reinforced steel tubular columns.To consider the impact of this factor,we calculate the strengthening capacity of 18 longitudinal full-enclosed steel tubular columns in 6 groups with a range of lambda=30-60 by ABAQUS.Comparing the results with the theoretical bearing capacity and considering the influence of interface failure,the revised coefficient₍（8） is introduced to draw a curve of_（8）-9of the scaled component at the location.Finally,based on the research results of full-scale specimens,the envelope curve of_（8）-9suitable for engineering practice is proposed.1.We study the effect of carbon fiber spaced steel tube on the mechanical properties of components.The failure mode,ductility development,bearing capacity change,transfer of control section and the role of carbon fibre in steel tube with bonding intervals of 30mm,50 mm and 80 mm were studied by experiment and numerical simulation.Additionally,ABAQUS was used to analyze the density of paste interval.The performance changes of components at 40 mm and 60 mm intervals are simulated respectively.Finally,five groups of components are compared together,and the construction measures of carbon fiber spaced sticking column with 1/4³/4 length are obtained.It provides a reference for the supplement of structural measures in the Technical Specification for Reinforcement of Steel Structures（CECS77:96）.3.In the process of establishing the finite element model,the bonding layer and CFRP are combined into a composite material,and the properties of the composite material are given respectively.Then the composite material is contacted with the steel pipe to simulate the common forces of the actual medium glue,CFRP and steel pipe.This treatment method also takes into account the role played by the actual medium glue layer.Finally,the validity of the construction method of carbon fiber spaced steel columns is verified in this paper.That is to say,CFRP interval wrapped steel tubular column can improve the bearing capacity of members,but the increase of bearing capacity is not more than 7%.The recommended bonding interval of CFRP between 30 and 40 mm can significantly improve the ductility of components,and the minimum difference between other intervals is 15.66%.The test results show that CFRP wrapped with 30mm interval can play a significant role in 1/3 of the column length,and CFRP wrapped with 50mm interval and 80mm interval can play a significant role in 1/6 of the column length.CFRP wrapped with 30mm interval can give full play to its role,and cooperate with the steel pipe column to form a good force-bearing entirety.In addition,the envelope curve of the correction factor of the reinforcement bearing capacity for full-scale members is obtained.It is found that the floating range of₍（8） is between 0.98 and 1.08,and with the increase of slenderness ratio,₍（8） also increases,but the value of₍（8） is the largest when the number of sticking layers of the same component is two.