Research On Mechanical Behavior Of Eccentrically Loaded High Strength Concrete Filled High Strength Square Steel Tubular Columns With The Steel Above Q550

With the progress of building engineering technology,building structure is developing towards the direction of light weight,high strength,high rise and large space.Small section,large bearing capacity,saving space and improving economic benefit have become the goal of current building engineering design.Because of this,high strength concrete and high strength steel are increasingly used in major load-bearing components.Compared with the use of normal strength concrete filled steel tube(CFST),the section size and space area of the high-strength steel tubular(CFST)columns formed by high-strength steel and high-strength concrete structures can be greatly reduced.It can meet the requirements of long span,high height,heavy load and bear harsh conditions,and meet the requirements of modern industrial construction technology.In this paper,the bias tests of 6 concrete filled square tube short columns with high strength steel and concrete and 9 middle long columns of high strength concrete filled steel tube are carried out.The failure morphology,load-deflection curve,load-strain curve,plane section assumption,load-Poisson's ratio curve and second order effect were analyzed.Finite element model of bias columns of high strength square steel tube and high strength concrete was established by ABAQUS finite element analysis software.The accuracy of the model is verified by comparing the model results with the experimental results.The stress characteristics,stress and strain distribution of steel and concrete,load sharing and interaction between steel and concrete were analyzed.The influence of the main variables on the ultimate bearing capacity and initial stiffness of high-strength concrete filled steel tubular columns was studied by changing the yield strength of steel,strength of concrete,steel content,eccentricity,and ratio of length to thickness.Combined with the experimental results and the simulation analysis,the relevant calculation formulas for columns of high strength square steel tube and high strength concrete under bias compression are proposed.The results are compared with the test results to analyze the applicability of the formula to the bias columns of high strength square steel tube and high strength concrete.The results show that the whole process of the unidirectional bias columns is divided into elastic stage,elastic-plastic stage,plastic strengthening stage and descending stage.The interaction between steel tube and core concrete is mainly concentrated in the corner area,while the interaction between other flat areas is very small.Short column in the P-? curve rising stage,the bearing capacity of the specimen is mainly borne by the concrete.After the specimen reaches the ultimate bearing capacity,the load Shared by concrete gradually decreases.In the whole process of loading,the concrete bears more loads.The ultimate bearing capacity of unidirectional bias columns of high-strength square steel tube and high-strength concrete increases with the increase of steel yield strength,concrete strength and steel content,and the increase trend is linear,while the decrease trend is non-linear with the increase of eccentricity and ratio of length to thickness.The yield strength of steel has little effect on the initial stiffness of unidirectional bias columns of high strength square steel tube and high strength concrete.With the increase of concrete strength and steel content,the initial stiffness of members increases approximately linearly.The initial stiffness decreases with the increase of eccentricity and gradually decreases in a small range.In this paper,the formula for calculating ultimate bearing capacity of unidirectional biased columns of high strength square steel tube and high strength concrete is presented.This formula is suitable for calculating the ultimate bearing capacity of columns of high strength square steel tube and high strength concrete subjected to bias compression.