On deformation and failure of brittle solids: Some outstanding issues

Certain fundamental issues concerning the experimental basis for current phenomenological constitutive models of rock and concrete are discussed. Problems related to both quasi-static and dynamic response are treated. Within the first category are included the topics of strain softening, strain hardening, failure states, and failure modes below the brittle-ductile transition. The second category focuses upon the task of determining the strain rate-dependent of material properties. In addition to the above, a class of theoretical modeling problems is discussed. Emphasis here is placed on the application of homogenization techniques in conjunction with micromechanics to develop nonphenomenological models of rock and concrete. An example application of this methodology to reinforced concrete is presented in an effort to demonstrate the superior modeling capabilities that can evolve from such an approach.