Numerical and Experimental Study of the Mechanism of Torsional Flutter for OpenCrossSection Composite Beams

Abstract:

Computational fluid dynamics and experimental methods are utilized to study the flutter characteristic and countermeasure mechanism of opencrosssection. The wind tunnel test results show that the prototype section of one suspension bridge tends to suffer flutter instability at relatively low wind speeds. The flutter critical wind speed is obtained by using the CFD approach, which conforms well with wind tunnel test results. Numerical simulations show that vortex shedding and drift from the lower surface of the section at high wind speeds match with the torsional displacement of the deck section. Vortex drifting produces the same direction aerodynamic torque as the section movement direction, leading to a flutter divergence. The same calculation is done with three sections added with different types of stabilization plates. The existence of stabilization plate prohibits the development and movement of main vortices, resulting in aerodynamic forces acting on the girder related less to displacement, thus suppress the flutter. Sectional and aerodynamics model wind tunnel tests are conducted to prove the effectiveness of stabilization plates. The results show that the lower stability plate is an effective vibration suppression measure for the flutter of the opencrosssection.

Key words:opencrosssection composite beam; vertical stabilization plate; vortex shedding mechanism; aerodynamic derivatives; bridge flutter