Study On Axial Compressive Properties Of Thin-walled Steel Confined Square Timber Columns

In recent years,it has become a research hotspot in the field of green construction and assembly construction,and has become a hot spot in the field of green construction.Therefore,based on the existing composite structures,a thin-walled steel restrained square wooden column is proposed,which is directly embedded into the square steel pipe,and the bolt is used to pull the surface of the external steel pipe to produce the initial transverse tensile stress,so that the wooden column is in the state of three-dimensional compression at the initial stage of loading.When the composite column bears the vertical load,the external square steel pipe limits the transverse deformation of the wooden column,while the core wooden column limits the inward buckling deformation of the square steel pipe.This interaction between the steel pipe and the wooden column improves the bearing capacity of the composite column.In order to study the axial compressive properties of thin-walled steel confined square timber columns,the following work is carried out in this paper:(1)Through the material mechanical property test,the air dry density,moisture content,elastic modulus,Poisson’s ratio,compressive yield strength and compressive ultimate strength in three directions were measured and obtained;The tensile yield strength and ultimate tensile strength of thin-walled steel are obtained through the tensile test of steel;Clarify the mechanical properties of bolts.(2)Taking the reserved amount and initial prestressing force of the core wood column as variables,eight thin-walled steel restrained square wood column specimens were designed and fabricated.The axial compression test was carried out on the specimens,and the axial compression bearing capacity,stiffness and ductility of the specimens were analyzed.The test results show that the thin-walled steel confined square timber column has good bearing capacity,stiffness and ductility;Compared with pure wood column specimens,the maximum increase rate of axial compression ultimate bearing capacity is 33.2%,the maximum increase rate of stiffness is 98.8%,and the maximum increase rate of ductility is297.8%.(3)The numerical model of the specimen is established by using ABAQUS software,and the displacement loading is the same as that of the test.The calculated results are compared with the test results,and it is found that they are in good agreement.Then,the expansion parameters of the initial pre stress and the wall thickness of the steel pipe are analyzed.The results show that when the initial pre stress is between 0.10-0.30,the ultimate bearing capacity of the composite column will increase with the increase of the initial pre stress;Increasing the wall thickness of steel pipe will increase the bearing capacity.(4)Combined with the test and numerical simulation results,the restraint mechanism of thin-walled steel restrained square timber column is clarified.Referring to the calculation model of concrete-filled steel tubular composite short column with restraint tie rod,the restraint effect coefficient and slenderness ratio correction coefficient are introduced to simplify the formula,and the calculation formula of axial compression bearing capacity of thin-walled steel restrained square timber column is deduced.The error between the calculated value and the experimental value and numerical simulation value is within 15%.