Experimental study on the flutter stability of long-span bridges subjected to wind and rain

The flutter test, based on free vibration test of a s separated twin-box bridge section model, was carried out by considering the flutter stability of a long-span bridge under the simultaneous actions of wind and rain, utilizing the system of simultaneous actions of wind and rain built in an atmospheric boundary layer wind tunnel. Through analyzing the flutter derivatives and critical flutter wind speeds of the bridge model under different rainfall intensities, the flutter stability of the bridge influenced by rainfall was determined. Experimental results display large variations in the flutter derivatives for different rainfall intensities. The flutter derivative, which reflects the torsional aerodynamic damping action on torsional vibration, changes most significantly. Critical flutter wind speed increases at first then decreases with the enhancement of rainfall intensity. The results show that rainfall may affect the flutter derivatives and critical flutter wind speeds of long-span bridges.