Microplane model for concrete. Part I. State of the art

The fundamental concepts of the microplane theory for non-linear modeling of concrete are presented in this paper. The basic idea behind the model is that the relationships between stress and strain are defined on planes of various orientations that represent microstructural damage planes, such as contact layers between aggregate pieces. Starting from the pioneering idea formalized as the slip theory of the plasticity, several models have been proposed in literature with the aim of formulating a general procedure for damage and fracture in concrete, under different loading combinations. The literature models are critically discussed with the aim to introduce an application presented in a companion paper: the application regards CFRP-confined concrete elements modeled at macro and meso-scale.