Finite Element Analysis Of Mechanical Performance Of ECC Components Based On Modified Compression Field Model

Engineered cementitious composites(ECC)is a fiber-reinforced cementitious composites characterized by high ductility,tensile hardening,and multiple dense fractures.Domestic and foreign scholars have conducted experimental research on the tensile,compression,bending and shear properties of ECC,and it is employed in beams,columns and other components to study their mechanical performance.In practical engineering,ECC components can be simplified as plane stress elements through reasonable assumptions,and then the mechanical performance of ECC components under load can be analyzed through finite element software.This paper takes Abaqus,a large general finite element program,as the platform to write ECC constitutive user subroutine through UMAT(User-Defined Material Mechanical Behavior)subroutine interface.Based on the modified compression field model,the transformation Angle expression,transformation matrix and Jacobian matrix between x-y and 1-2 coordinate systems are derived.The existing ECC uniaxial tension and compression constitutions are used and the compression softening effect caused by the main tensile strain is considered.Then the derivative of ECC and concrete stress with respect to strain,namely the specific value on the main diagonal of jacobian matrix,is solved.The subroutine flow chart and the variables used are given.In order to verify the accuracy of the subroutine,this paper has carried out a simulation analysis for the Reinforced Engineered Cementitious Composites beam,Reinforced Concrete/Reinforced Engineered Cementitious Composites column,small shear span ratio RECC shear wall and R/ECC composite joint.In the analysis of RECC beam,the loaddisplacement curve obtained by finite element analysis is in good agreement with the test results.Based on the finite element model,the influences of shear span ratio,longitudinal reinforcement ratio and stirrup ratio on the shear bearing capacity of RECC beam are studied.In the R/ECC composite column analysis,the influences of axial compression ratio,stirrup ratio,shear span ratio and longitudinal reinforcement ratio on its mechanical performance were studied after verifying the correctness of the subroutine.In the RECC shear wall with small shear span ratio,the subroutine can predict the mechanical performance of components and analyze the changes of the shear bearing capacity of components with ECC strength,shear span ratio,axial compression ratio and reinforcement ratio of vertical distributed reinforcement.In the R/ECC joint analysis,the influence of its mechanical performance with axial compression ratio and joint area stirrup ratio is studied.Through the calculation of the bearing capacity error value of the ECC component in the paper,it shows that the subroutine developed in this paper can analyze the mechanical performance of ECC components under the action of monotone load.