AERODYNAMIC OPTIMIZATION OF A TWIN-BOX DECK BASED ON FLUTTER STABILITY ADOPTING CFD APPROACH

Abstract

Twin-box bridge decks offer a very good aerodynamic response in terms of flutter stability. Because of this, they are being adopted in some of the most challenging long span bridges recently built such as the Stonecutters Bridge. The importance of bridge aerodynamic investigations was immediately realized after the Tacoma Narrows Bridge collapsed in 1940. Since, the cable-stayed bridges are prone to the aerodynamic instabilities caused by wind this becomes a prime criterion to be checked during the design. The target is to optimize the deck shape to reduce the aerodynamic forces. To achieve this goal, more than 40 model cases were tested in order to obtain an optimized aerodynamic configuration of the deck. The influence of the gap distance between twin-box and the geometry modifications on the aerodynamic stability has been established through this thesis. CFD (Computational Fluid Dynamics) simulations appear to be powerful rivals of the wind tunnel tests, which are expensive, require a scale model and a time consuming tool in designing bridges. Therefore, the analyses are carried out for deck shapes through CFD software OpenFOAM V2.3.1, establishing a dimensional fluid-structure interaction (FSI) numerical model to calculate the flutter critical wind speed.