Study On The Eccentric Compression Performance Of Concrete-encased CFST Columns Strengthened By CFRP After Fire

The main research direction of this paper is to use the composite fiber material carbon fiber cloth to strengthen the concrete-filled steel tube composite column after fire and to study its eccentric pressure performance.The article first explains the parameter design concept of the finite element simulation part of the composite column after fire,and then uses ABAQUS to establish the temperature field model of the concrete-filled steel tube composite column,the mechanical model after the fire and the finite element model after the carbon fiber cloth reinforcement.The obtained data and simulation results verify the feasibility and accuracy of the model.When the verification is successful,the influence of the use of different carbon fiber cloth reinforcement methods and the number of reinforcement layers on the change trend of the bearing capacity of the reinforced composite column is analyzed.On this basis The influence of the barrier eccentricity on the reinforcement effect is also studied.In the entire analysis process,the following 6 important conclusions are drawn:(1)In the study of the influence of fire time on the mechanical properties of concrete-filled steel tubular composite columns after fire,it is found that when the ratio of concrete-filled steel tubular and eccentricity and other parameters are consistent,when the fire time reaches 60 minutes,the change trend of the bearing capacity and the range of the ultimate bearing capacity of the composite columns are very small,which is the basis for the later study of CFRP strengthened composite columns after fire.The reliable range of fire time is provided.(2)When using the side bonding method to paste carbon fiber cloth,when the total number of layers of carbon fiber cloth is more than 3,no matter what kind of vertical and horizontal carbon fiber cloth paste ratio can not make carbon fiber cloth play a good role in reinforcement,this is because when the number of layers of carbon fiber cloth is more,the carbon fiber cloth can not work well with each other,and the utilization rate of the outer carbon fiber cloth is lower.(3)After considering the cost performance and the actual construction technology,it can be determined that the best reinforcement method is to stick a layer of carbon fiber reinforced polymer(CFRP)in the longitudinal and transverse directions by using the lateral bonding method.The ultimate bearing capacity of the concrete-filled steel tubular(CFST)composite long columns strengthened by this method after 60 minutes of fire is about 14.11% higher than that of the unreinforced specimens.(4)When the transverse winding method is used to reinforce the post fire composite members,the ultimate bearing capacity of the strengthened specimens has a linear relationship with the number of strengthened layers,and the bearing capacity of the specimens increases with the increase of the number of strengthened layers.However,when the number of strengthened layers reaches 5 or more,the bearing capacity of the composite columns basically does not increase.When the number of strengthened layers reaches 5,the ultimate bearing capacity of the composite columns increases by 17.62%.(5)When the reinforcement method and the number of reinforcement layers are the same,the eccentricity has a certain impact on the reinforcement effect of the post-fire laminated column subjected to the bias load.The specific performance is that the reinforcement efficiency increases with the eccentricity.The increase and decrease.(6)The article finally puts forward the practical calculation formula of the eccentric pressure of the reinforced laminated column under the reinforcement scheme of the transverse winding method with the number of reinforced layers as the variable parameter,and the established bearing capacity calculation formula can better predict the post-reinforcement The load-bearing capacity of the test piece.