Study On The Mechanical Properties Of Concrete Filled High Strength Cold-formed Steel Tubular Columns

Concrete filled steel tubular structure has been widely used in the construction industry because of its good mechanical properties.The majority of scholars have conducted in-depth research.The cold-formed steel concrete structure maintains advantages of ordinary concrete filled steel tubular structure,also has less weld,welding quality is easy to guarantee;and can shorten the time of making project;The residual stress and residual deformation are smaller in the production process.At present,the research of cold-formed concrete filled steel tube with Q235 and Q345 of steel is mainly object.Little research on high strength steel.Therefore,this paper studies the influence of the change of width thickness ratio,length width ratio and steel grades on the bearing capacity of the cold-formed steel tube concrete under the axial compression load.In this paper,axial loading performance of concrete filled high strength cold-formed steel tubular columns experiment is studied and finite element analysis is carried on.The number of test pieces is 20.The height of pieces is 600 mm.The section size are 100 mm × 200 mm,150mm × 200 mm,200mm ×200mm.steel thickness are 4mm,5mm,6mm.Steel grades are Q345,Q390 and Q420.The work done in this paper is as follows:(1)The axis of concrete filled high strength cold-formed steel tubular columns under axial pressure loading and the specimens' capacity is studied.The relation between the axis load and longitudinal strain,lateral strain and failure modes of the specimens are also studied.And the bearing capacities of concrete filled steel tube columns are calculated.Through experiments this paper analyzes the steel grades,width-thickness ratio and length-width ratio on the bearing capacity of recycled concrete filled steel tube columns.(2)Establish appropriate constitutive relation of core inside concrete and outside steel tubes,using the finite element software Abaqus.This paper established finite element model of recycled concrete filled steel tube and simulated square steel tube recycled concrete short columns under axial compression loading.Adjust of the finite element model to make it consistent with the experiment,drawing the curve of loadlongitudinal displacement and simulating the damage form of specimens,this paper compare the numerical simulation with experimental results.(3)Based on the simulation of concrete filled high strength cold-formed steel tubular under axial pressure,performing the parameters analysis of the specimens,the influence of steel grades,width-thickness ratio and length-width ratio on axis compressive strength of concrete filled high strength cold-formed steel tubular is considered.A total of 27 specimens.The results of finite element simulation using nonlinear regression method to fit the data,and finally put forward a simplified formula for calculating the bearing capacity of axial compression.