Study On Mechanical Properties On Normal Section Of Composite Crisscross-section Concrete-filled Steel Tubular Columns

In this paper,through axial compression test and eccentric compressive test,the final damage form and relative measurement curve of each specimen are obtained.Then,through the finite element software ABAQUS,the whole process of axial compression and biasing is modeled and analyzed.Finally,based on the experimental and finite element simulation analysis,the simplified formula for calculating the axial compression and ultimate load carrying capacity of the composite cross section concrete-filled steel tubular column is recommended.The main research work of this paper is as follows:(1)5 composite crisscross-section concrete-filled steel tubular columns were designed.The main parameters were specimen length and section form,and the failure modes and the measured data were compared.The results show that,with the increase of the length,the bearing capacity of the specimen decreases obviously,but the stiffness of the elastic phase has no obvious change.For the specimens of the same length,the bearing capacity of the B section is significantly higher than that of the A section because of the existence of the appendage,and the overall stiffness is slightly larger than that of the A section.(2)6 composite crisscross-section concrete-filled steel tubular columns were designed,The main parameters are the length of the specimen and the eccentricity ratio,and the failure modes and the measured data were compared.The results show that the ultimate bearing capacity of specimens decreases with the increase of specimen length and eccentricity.The increase of specimen length has little effect on the stiffness of elastic phase,and the increase of eccentricity makes the stiffness of elastic phase decrease.(3)Reference to the finite element modeling method for the axial compression and eccentric compression of concrete filled steel tubular members with special shaped columns by ABAQUS.The modeling and analysis of 11 composite crisscross-section concrete-filled steel tubular columns(5 axial compression specimens and 6 bias pressure test pieces)are carried out.Considering the particularity and strong constraint effect combination cross section of the steel pipe concrete column shape,select the constitutive model for the concrete composite cross tube column filled concrete,load model calculated strain and load longitudinal compression curves and experimental curves were compared.(4)On the basis of verifying the correctness of the modeling method,the working mechanism of axial compression is analyzed.The results show that the concrete composite cruciform steel tube concrete column of square steel tube column with concrete filled square steel tubular column ordinary,has higher bearing capacity and better ductility;the restrained effect of the steel tube in the composite crisscross-section concrete-filled steel tubular column on the concrete is stronger in the corner and weaker in the middle of the web..(5)The reference concrete at home and abroad and the steel tube columns axial compressive capacity specification and related literature,suggests the axial compressive applicable to composite crisscross-section concrete-filled steel tubular columns bearing capacity calculation formula,and the formula of the calculated results were compared with the test results,verify the correctness of the calculation formula.