Quasi-steady analysis of a two-dimensional bridge deck element

Many techniques have been proposed in the last years for the study of the aeroelastic problems in civil engineering. The mechanical behavior of bridges under wind action can be identified through experimental campaigns or numerical procedures. Numerical tests require an adequate load model to describe the wind action, that has a turbulent stochastic structure, and a suitable structural model for each bridge. The effect of turbulence in the wind loads is often be captured by considering an equivalent average of the measured quantities. Experimental tests are commonly performed on two-dimensional systems, providing useful data for numerical models, while finite element models can give a complete representation of the overall behavior. At an intermediate stage, cross-sectional analyses can be performed, to be compared with the experimental tests, and to understand the interaction between a single bridge deck strip and the wind flow. This type of two-dimensional model allow us a physical interpretation of the different contributions involved. Moving back to the basis of the theory, the limits and the possibilities of a quasi-steady approach in the load modeling are investigated, in order to analyze the effects of the widely used linearizations in the computations concerning the fluid-structure interaction and to compare steady and unsteady formulation. The present paper is devoted to study a quasi-steady load model related to physically significant aerodynamic quantities and to develop numerical examples of such a system subjected to aeroelastic loads, in order to analyze its qualitative and bifurcative behavior and evaluate the critical flutter speed. The same model accounting for aerodynamic non-linearities is proposed and discussed.