Bridges, Tunnels and other Transportation Structures
Wind loading is one of the critical parameters for the design of long-span bridges due to their inherent low stiffness and damping. The analysis of the dynamic behavior of long-span cable-stayed and suspension bridges under wind excitation is usually performed on the basis of experimental tests on physical models in wind tunnels. Recently, Computational Fluid Dynamics (CFD) has been gaining attention towards its general use in bridge design problems. From the late 1990s, the number of references dealing with the numerical simulations of aerodynamic and aeroelastic problems in bridges has certainly increased and the accuracy in the simulations has definitely improved due to improvements in modeling formulation, computer power and software.
The objective of this research is to utilize CFD to study the response of long-span bridges due to wind induced instabilities such as flutter and vortex-induced vibrations. The critical flutter wind speed is deduced through numerical modeling of wind using data obtained from CFD analysis using ANSYS-CFX software. For simulating the airflow around the bridge deck, the SST turbulence model was used. The bridge section was rotated by +/- 5 degrees around its mass center of rotation. Forces and Moments are recorded and used to determine the critical wind speed. A streamlined bridge deck was used for this study. Parametric studies are performed for better understanding of the limits with the proposed methodology and its commercial application. Data from wind tunnel testing were used for assessing the accuracy of CFD simulations. A good agreement between the CFD and wind tunnel results was obtained. Results are expected to enhance the state of the art knowledge in using CFD for studying the response of long-span bridges under wind loads and reduce dependence on wind tunnel testing. An assessment of the accuracy and computational time will allow bridge designers to make engineering decision when to use CFD vs wind tunnel.
This paper should be of interest to bridge designers, academic researchers and code developers.