Study On Strain-softening And Tension-stiffening Of Reinforced Concrete Structure

Concrete is a highly nonlinear material,which has the characteristics of strain-softening,distinctively differences in compression and tension mechanical response,and prone to crack.Strain-softening is one of the important mechanical behaviors of concrete at medium and low confining pressures.The results of numerical calculations on concrete are prone to mesh-size-dependency and boundary value problems.Mesh-size-dependency is mainly reflected in the following: the energy dissipation approaches zero with increasing refinement of the discretization of the finite element violating obviously the law of conservation of energy.Boundary value problems cause mesh-bias-dependency which means that the numerical solution cannot properly capture the direction of the strain localization band.Tension stiffening is one of the important working mechanism of reinforced concrete structure,its modelling affects the correct evaluation of the stiffness,stiffness and load carrying capacity.Strain-softening model of concrete,constitutive models of steel and tension stiffening model of reinforced concrete and are reviewed.The methods to solve mesh-sizedependency and boundary value problems are summarized,and the application of the methods is also described.Two tests of reinforced concrete flexural beams are designed to describe the entire stress state of reinforced concrete,and analyze the datum in the load carrying capacity,stiffness,mid-span deflection,etc.Based on the smeared crack model within the framework of continuum mechanics,using the combination of user subroutine and ABAQUS,simulating one-dimensional concrete bar loaded in tension,concrete specimen loaded in uniaxial tension,concrete specimen loaded in uniaxial compression,four-point bending plain concrete beam,and four-point bending reinforced concrete beam,numerical results of four-point-bending plain concrete beam and reinforced concrete beam are basically consistent with the experimental results.Theory versus experiment comparisons indicate that the smeared crack model solves mesh-size-dependency problem and furnishes a capability to accurately describe the macroscopic mechanical behavior of the structure.The reasonable tensile stiffening model is conducive to a correct evaluation of the deformation and bearing capacity.