Critical Tensile Strain of Plain Concrete under Biaxial Stress

Abstract

Failure of concrete has been discussed mainly in the stress system. However, the failure strain system is also important for structural analysis. This paper delineates the failure strain system of plain concrete under biaxial stress, by obtaining the critical tensile strain, namely the maximum principal strain at failure, and by examining the author's results of axial force-internal pressure tests.
The conclusions obtained are as follows :
(1) The critical tensile strain of plain concrete can be expressed by the following simple linear equation with octahedral normal stress at failure.
ε_cr=aσ_oct+b
Where 'a' and 'b' are the constants obtainable from the strengths and the critical tensile strains in uniaxial compression and tension tests.
(2) The octahedral failure stress of plain concrete under the state of tension-compression can also be approximated by a simple linear equation. However, the octahedral failure stress under the state of biaxial tension deviates from this equation.
(3) The results of axial force-internal pressure tests can be explained well by the critical tensile strain theory.
(4) The critical tensile strain theory is applicable for the strength of plain concrete under the state of biaxial tension as well as under the state of compression-tension.