Cellular Finite Beam Element for Nonlinear Analysis of Concrete Structures under Fire

Abstract

A novel approach to nonlinear finite-element analysis of concrete structures exposed to fire is presented. The proposed formulation refers to frame systems, but it can be extended to other types of structures. The main novelty of this formulation is the use of a special class of evolutionary algorithms, known as cellular automata, to describe the heat transfer process induced by fire and to create an effective link between the simulation of the thermal process and the structural analysis. The heat transfer process is reproduced by considering heat conduction, heat convection, and thermal radiation. The temperature effects on the structural performance are taken into account by means of temperature-dependent thermal and mechanical properties of concrete and steel. In this way, the general criteria for nonlinear finite-element analysis of concrete structures are applied to formulate a cellular reinforced concrete beam element with temperature-dependent characteristics. The effectiveness and applicability in engineering practice of the proposed formulation is demonstrated through applications. The results prove the accuracy of the proposed procedure and show that, for statically indeterminate structures, fire safety needs to be evaluated at the global level by taking into account the actual role played by the structural scheme.