A REPORT ON AEROELASTIC ANALYSIS OF BRIDGE GIRDER SECTION USING COMPUTER MODELING.

This report describes the numerical simulation of wind flow around bridges using the Finite Element Method (FEM) and the principles of Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD). Since the suspension bridges are prone to the aerodynamic instabilities caused by wind, this becomes a prime criterion to be checked during the design. If the wind velocity exceeds the critical velocity for flutter that the bridge can withstand, then the bridge fails due to the phenomenon of flutter. Tacoma's narrows bridge failure in Washington, USA is a classical example of this failure. Larsen and Walther (1997) used the Discrete Vortex Method (DVM) similar to the wind tunnel procedures. In this work, the computations are carried out for both the fixed and the moving bridge conditions. A Large Eddy Simulation (LES) turbulence model is used and the rigid body grid movement technique is adopted. The critical velocity for flutter is calculated directly using the free oscillation procedure similar to the approaches reported by Selvam et. al (1998 and 2000). The influence of grid on critical velocity is also studied. The computed critical velocity for flutter is in good agreement with the wind tunnel measurements. The conditions of flutter and no flutter are demonstrated clearly using the response of the bridge in time.

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