Cellular automata approach to durability analysis of concrete structures in aggressive environments

This paper presents a novel approach to the problem of durability analysis and lifetime assessment of concrete structures under the diffusive attack from external aggressive agents. The proposed formulation mainly refers to beams and frames, but it can be easily extended also to other types of structures. The diffusion process is modeled by using cellular automata. The mechanical damage coupled to diffusion is evaluated by introducing suitable material degradation laws. Since the rate of mass diffusion usually depends on the stress state, the interaction between the diffusion process and the mechanical behavior of the damaged structure is also taken into account by a proper modeling of the stochastic effects in the mass transfer. To this aim, the nonlinear structural analyses during time are performed within the framework of the finite element method by means of a deteriorating reinforced concrete beam element. The effectiveness of the proposed methodology in handling complex geometrical and mechanical boundary conditions is demonstrated through some applications. Firstly, a reinforced concrete box girder cross section is considered and the damaging process is described by the corresponding evolution of both bending moment-curvature diagrams and axial force-bending moment resistance domains. Secondly, the durability analysis of a reinforced concrete continuous T-beam is developed. Finally, the proposed approach is applied to the analysis of an existing arch bridge and to the identification of its critical members.