Multi-directional modeling of crack pattern in 2D R/C members

A macro-scale approach to R/C modeling is proposed in this paper by formulating a comprehensive model, that describes R/C behavior in the uncracked stage (solid concrete) and in the cracked stage, the latter with either unidirectional cracking (primary cracks) or with bidirectional cracking (primary and secondary cracks) or even multi-directional cracking. The secant stiffness matrix is formulated by means of a direct procedure, based on the assumption that the solid concrete and the reinforcement work in parallel, while the solid concrete between the cracks and the cracks themselves work in series. The resistant mechanisms active at the crack interface are introduced by means of their highly nonlinear laws, that are taken from the literature and are based on well-documented tests. The reliability and accuracy of the proposed model are checked against a few well-documented tests on 2D R/C members failing past the formation of secondary cracks.