Micromechanics-based constitutive model for interface shear

This paper presents a new constitutive model for interface shear in strain-softening composites. The composite, in this case portland cement concrete, is treated as a single-phase medium with no distinction in the strength difference between the cementing matrix and the coarse aggregate inclusions. The principles of micromechanics were used to capture the different mechanisms of interface shear. The model consists of an assemblage of springs and a triangular asperity as a statistically equivalent replacement of the rough crack surfaces. The constitutive model relates the normal and shearing stresses on the rough crack to the corresponding displacements in terms of the interface strength, contact areas, the contact angle of the rough crack surface, and the crack closing pressure. The performance of the constitutive model is verified by predicting experimental results with varying crack width and normal stress as well as constant crack width and constant normal stress. The comparison between predicted and experimental results appears to be satisfactory.