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Experimental aerodynamical modeling of a generic bridge-deck section

Wind is a major natural phenomenon that needs to be considered while designing structures such as bridges. In wind-prone areas, it can cause large loads on bridges, followed by instabilities that lead to reduced performance, fatigue, or even failure. Its effect on structures can be investigated using various methods. In this thesis, the focus is on the experimental wind- tunnel testing method. Two small-scale sectional models were made, each representing a generic box- girder bridge section with different width-to- depth ratios. Experiments were carried out in a boundary layer wind tunnel at the Inter-University Research Centre on Building Aerodynamics and Wind Engineering (CRIACIV) at the University of Florence, Italy. Static and dynamic tests were conducted in high- and low-turbulent flows. Aerodynamic loads (drag force, lift force, and pitch moment) were measured by a pair of high- frequency force balances for various flow incidence angles. Dynamic measurements were performed by the system containing a pair of optical lasers and shear-type frames for three different flow incidence angles. The dynamic response was determined for a single degree of freedom in a vertical direction. The results indicate that aerodynamic loads in high- and low- turbulent flows have similarities in the trends observed on both models. However, a smaller width- to-depth ratio model is characterized by greater magnitudes of forces and moments. Dynamic test results indicate that the larger width-to-depth ratio model starts to oscillate at two different flow velocities. The model oscillates at a lower flow velocity due to secondary resonance at all flow incidence angles in a low-turbulent flow, while only the model at the flow incidence angle of +3 degrees oscillates at a higher flow velocity due to galloping.

Bridge section ; aerodynamic forces and moments ; dynamic response ; boundary layer wind tunnel

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