Keywords: concrete structures, transport processes, fire damage, corrosion, lifetime performance, cellular automata.

In recent years, relevant advances have been accomplished in the fields of modelling, analysis, and design of deteriorating civil engineering systems [4]. For concrete structures, novel approaches to time-variant assessment and lifetime optimisation of structural performance have been proposed [1,2,3,5,6]. The main novelty of these approaches is the use of a special class of evolutionary algorithms, known as cellular automata, to simulate the transport processes of mass and heat and to describe the corresponding mechanisms of damage propagation. The aim of this study is to present a review of cellular automata approaches to lifetime prediction of concrete structures exposed to fire or aggressive environments.

For concrete structures exposed to fire, cellular automata are used to describe the fire-induced heat transfer process, including heat conduction, heat convection and thermal radiation, and to create an effective link between the thermal process and the structural behaviour. The temperature effects on the structural performance are evaluated based on temperature-dependent laws for both the thermal and mechanical properties of the component materials, concrete and steel, and by taking into account the additional deformative effects induced by heat transfer [6].

The lifetime performance assessment of concrete structures under diffusive attack from external aggressive agents is based on similar criteria. Cellular automata are used to reproduce the diffusion process and to model the mechanical damage coupled to diffusion, including deterioration of concrete and corrosion of reinforcement. The interaction between diffusion and concrete cracking is also taken into account by a proper modelling of the stochastic effects in the mass transfer [1].

Based on general criteria of finite element modelling of concrete structures, the coupling between the transport processes and structural behaviour leads to the cellular automata formulation of finite elements with time-variant properties for non-linear analysis of deteriorating concrete structures [1,6]. The proposed models are validated by comparing the results of numerical predictions with the results of experimental tests. The effectiveness and general applicability in engineering practice of the approaches presented is demonstrated through case studies related to a continuous beam under fire and an existing arch bridge exposed to corrosion. The deterministic developments reviewed in this study provide a basic framework for a general probabilistic approach to lifetime structural reliability of concrete structures [2,3,5].

[1]

F. Biondini, F. Bontempi, D.M. Frangopol, P.G. Malerba, "Cellular Automata Approach to Durability Analysis of Concrete Structures", Journal of Structural Engineering, ASCE, 130(11), 1724-1737, 2004.

[2]

F. Biondini, F. Bontempi, D.M. Frangopol, P.G. Malerba, "Probabilistic Service Life Assessment and Maintenance Planning of Concrete Structures", Journal of Structural Engineering, ASCE, 132(5), 810-825, 2006.

[3]

F. Biondini, D.M. Frangopol, "Probabilistic Limit Analysis and Lifetime Prediction of Concrete Structures", Structure and Infrastructure Engineering, 4(5), 399-412, 2008.

[4]

F. Biondini, D.M. Frangopol, (Editors), "Life-Cycle Civil Engineering", CRC Press, Taylor & Francis Group, 2008.

[5]

F. Biondini, D.M. Frangopol, "Lifetime Reliability-Based Optimization of Reinforced Concrete Cross-Sections under Corrosion", Structural Safety, 31, 483-489, 2009.

[6]

F. Biondini, A. Nero, "A Cellular Finite Beam Element for Nonlinear Analysis of Concrete Structures under Fire", Journal of Structural Engineering, ASCE, 137(5), 543-558, 2011.

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