1 INTRODUCTION Wind action is one of the most determining factors for the safety of large and flexible structures. As it is well known, since the famous Tacoma Narrows Bridge failure of 1940, the design of long span cable-stayed and suspension bridges requires careful study of their aeroelastic behaviour under wind loads. Traditionally, this kind of work has been based on physical models tested in wind tunnels. More recently, an alternative numerical approach has been developed and refined. This empirical theory, based on the so-called Scanlan model for the evaluation of the wind forces (aeroelastic forces), involves important simplifications, which depend on the aeroelastic phenomena to be considered. However, this analytical approach requires the identification of some coefficients (drag, lift, moment coefficients and flutter derivatives). They are usually obtained from experimental studies on sectional bridge models in wind tunnels, though recent developments of Computational Fluid Dynamics (CFD) allow an alternative numerical approach. In this context, the main objective of this paper is to present a new methodology for the integral aeroelastic analysis of slender structures, based on the appropriate conjugation of an algorithm of Computational Fluid Dynamics (Finite Volume Method) with an algorithm of linear or geometrically non-linear analysis of structures. The computer code developed on the basis of this new methodology was applied to the aeroelastic study of a simply supported slender bridge deck, with rectangular cross-section. 2 INTEGRAL AEROELASTIC ANALISYS The computational algorithm developed to simulate aeroelastic phenomena in slender structures is a time incremental approach based on two numerical algorithms working together: one of them determining the fluid flow action and the other one evaluating the structural response. The numerical procedure used to calculate the fluid flow and its action on structures is based on the Finite Volume Method. The Finite Element Method is used to model the structural dynamic behaviour, which can be idealised as geometrically non-linear. 2.1 Fluid flow simulation The program, based on the Finite Volume Method (Patankar 1980, Versteeg 1995, Ferziger 1996), is suitable to simulate incompressible and isotherm bidimensional unsteady fluid flows around obstacles. It is assumed that the flow domain may be discretised in a control volume mesh, whose faces have vertical and horizontal directions. Differential forms of the general transport equations are discretised using a hybrid differentiation scheme. To reduce false diffusion, the quick differentiation scheme is also used in deferred correction context. Alternate value fields are avoided on the basis of a staggered grid approach. Solution procedures for transient calculations are implemented adapting under-relaxation factors depending on time increment. The high Reynolds number k – ε turbulence model is applied to simulate the flow turbulence (Rodi 1980, Tennekes 1980, Hossain 1982 and Oliveira 1990). Aeroelastic analysis of a slender bridge deck based on a Computational Fluid Dynamics algorithm A.V. Lopes Faculty of Sciences and Technology, University of Coimbra, Portugal, avlopes@dec.uc.pt Álvaro Cunha Faculty of Engineering, University of Porto, Portugal, acunha@fe.up.pt L.M.C. Simões Faculty of Sciences and Technology, University of Coimbra, Portugal, lcsimoes@dec.uc.pt ABSTRACT: This paper presents a new methodology for the aeroelastic analysis of slender structures, based on the appropriate conjugation of an algorithm of Computational Fluid Dynamics (Finite Volume Method) with algorithms for either linear or geometrically non-linear analysis of structures. The computer code developed on the basis of this methodology was applied to the aeroelastic study of a simply supported slender bridge deck, with rectangular cross-section. Some of the most meaningful results associated with the analysis of the corresponding aeroelastic instability are presented.