STUDY OF WIND EFFECT ON BRIDGES WITH DIFFERENT DECK SHAPES

Abstract

In the last few years, several bridges have collapsed due to extreme wind-loading events, especially cable-supported bridges and cable suspension bridges. Since cable-supported bridges are relatively lightweight and flexible, these bridges are more susceptible to collapse under wind load. The wind load effect on any bridge depends on the weight of bridge, the span of bridge, the material used to construct the bridge, and the shape of the bridge deck. Several ways exist through which the wind load effect on the bridge can be reduced, such as using fairings, changing the geometric shape of the deck, introducing roughness to the structural components of the bridge, etc. This study is focused on assessing the effectiveness of different shapes of the bridge deck and the use of fairings to minimize the wind load effect on the bridge. The first step towards this research work was to perform an extensive literature review to find the different types of bridge deck shapes and the use of fairings in the past to reduce wind load effects on bridges. Based on the reviews, the Lillebaelt shape of the bridge deck(Model-I) and the original deck shape of the Signature bridge(Model-II) are studied in detail. The use of fairings was adopted on the signature bridge classifying as Model-III (Full faired model) and Model-IV (Partial Faired model). The Signature bridge is located in Delhi and currently, the side face of the deck is flat which is not a good shape to reduce the wind load effect. The second step in this study was to decide the scale of the models which was used for experimental studies in the Wind Tunnel Laboratory of IIT Roorkee. Subsequently, the scaled models were fabricated using Whiteboard and suitable boundary condition was provided. The third step was to calibrate the load cell of the wind tunnel set-up under known lateral load. The boundary layer of the wind flow was assessed in the laboratory to find out the proper height for the models to be mounted on the load cell. The final step was to measure the magnitude of drag and moment experienced by all the models and comparisons were made to observe the behavior of all four models under wind with different speeds. Based on the experimental result, the magnitude of drag and moment was found to be lowest for Model I followed by Model and then Model-IV, and finally Model II. In conclusion, the deck shape of the Signature bridge can be modified to a Lillebaelt shape to reduce the magnitude of drag and moment up to 60%.