Investigation of flutter performance of a twin-box bridge girder at large angles of attack

Abstract

Twin-box bridge girders are considered to be aerodynamically favourable, and this paper presents a study on the flutter performance of this type of girders at large angles of attack by both wind tunnel tests and computational fluid dynamics (CFD) simulations. The stationary aerodynamic performance of a twin-box bridge girder at different angles of attack is studied, and different central slot widths are considered as well. Then, the flutter derivatives of the girder are extracted and the critical flutter state of the bridge is determined. The flutter mechanism is further discussed in detail based on the dynamic flow field characteristics and the work done by aerodynamic forces. Results show that the existence of central slot is in favour of the bridge flutter stability at null angle of attack. At large angles of attack, however, the flow field around the girder is quite different. Incoming flow could pass through the central slot and affect the vortex attaching to the girder. The upstream box extracts energy from the wind flow more easily than the downstream one, which may drive the bridge to torsional flutter instability at lower wind speeds.