The incremental version of Endochronic theory proposed by Bazant is a unified and comprehensive material model for concrete. This theory offers a possibility to accurately describe the behaviour of concrete under multiaxial stresses in a wide range of loading conditions without recourse to the concept of yield surface and the specification of unloading-reloading criteria.
However, this theory generally involves many functions and material parameters which are obtained by a rather complicated procedure. In the present paper, the effect of the change of material parameters on the stress-strain relationship is investigated. It is shown that sixteen out of forty-four parameters in the modified incremental version of Endochronic theory have much influence on the shape of the stress-strain curve.