Finite Element Analysis Of ECC-partially Encased Composite Column Subjected To Axial Compression And Compression-flexure Loading

With the rapid development of the construction industry,composite structure can give full play to the advantages of steel and concrete,so it is more and more widely used.PEC(Partially Encased Composite)column has a number of advantages,including the completion of concrete for enhanced local stability of the section of open steel and the reduction of the area of fire and corrosion resistance coating on the steel surface.However,low tensile strength,poor ductility and poor synergies with section steel affect the performance of PEC column.ECC(Engineered Cementitious Composite)is a kind of materials with high toughness,good ductility,and has good bond slip behavior with steel.Therefore,this paper proposes a ECC-Partially Encased Composite column,namely ECC-PEC column.In this paper,based on the existing PEC column test,the correctness of the finite element model of PEC column is verified,and the axial compression performance and bending performance of ECC-PEC column are simulated by finite element method.The results of axial compression simulation show that the failure mode of ECC-PEC column is steel flange buckling accompanied by ECC failure,and flange buckling occurs between two adjacent tie bars.The axial compressive bearing capacity can be increased by reducing flange width to thickness ratio,reducing tie bar spacing and increasing steel strength.Through the bending simulation results,it is found that the flange buckling of ECC-PEC column occurs at the position of the column foot,and different bending directions have a great impact on the failure mode of the model.When bending around a strong axis,the shaped steel flange plays a greater role in ECC constraint and has a significant influence on the improvement of PEC column bearing capacity.When bending around a weak axis,the transverse tie bar has less constraint effect on ECC,so the bearing capacity is relatively low.At the same time,axial compression ratio and length-width ratio are also important factors affecting the bending performance of ECC-PEC column.With the increase of axial pressure ratio,due to the greater stress generated by the PEC column at the column foot,the section steel flange under pressure yielded earlier,resulting in the reduction of horizontal bearing capacity and the rapid decline of post-peak bearing capacity.The bending performance of PEC columns with different length-width ratios is different,and the failure mode of long columns is more "brittle",and the second-order effect caused by the column length has a significant impact on the bearing capacity.The flange buckling is an important factor affecting the axial compressive and flexural performance of PEC column,the local buckling mode and mechanism of the flange after compression are analyzed,and a new formula for calculating the critical stress of the flange of ECC-PEC column is proposed,which is very important for calculating the bearing capacity of specimens.Based on the finite element analysis,the formulas for calculating the axial bearing capacity and flexural bearing capacity of ECC-PEC column are presented.Compared with the EC4 and CSA,the new formula can better calculate the axial and flexural bearing capacity of ECC-PEC columns.