Vortex models for aeroelastic assessment of multi element bridge decks

摘要

This paper presents vortex models for determination of the critical wind speed for onset of aeroelastic instability (binary flutter) of a twin-deck bridge. First a simple mathematical mdoel is presented, based on the vortex concept of classical two-dimensional potential flow theory. In this model the cross-flow due to bound vorticity and the trailing potential wake(s), is balanced by the cross-flow due to a prescribed oscillatory motion of the deck structure. The simple model yields a frequency domain representation of the motion induced forces which is directly applicable in standard flutter routines. Advanced discrete vortex models of twin and multi element decks are discussed which involves time domain simulation of the motion induced aerodynamic forces. The paper establishes the effect of the horizontal distance between deck elements on the aeroelastic stability. Stability predictions, based on the mathematical models discussed, are compared to existing wind tunnel test results of twin-deck configurations. Good agreement is demonstrated.