Experimental Study of Rain Effects on Vortex Shedding of Long Span Bridge Girders: Fid-Bau Portal

Experimental Study of Rain Effects on Vortex Shedding of Long Span Bridge Girders

Xin, Dabo / Li, Hui / Wang, Liang / Ou, Jinping

Vortex-induced vibration tests for a girder of a long-span bridge was carried out by studying vortex-induced vibration characteristics under the simultaneous actions of wind and rain, taking the separated twin-box girder section model as the research object specimen. A system providing simultaneous actions of wind and rain was built in the atmospheric boundary layer wind tunnel. After analysis of the amplitude-frequency characteristics of the vortex-induced vibration for different rainfall intensities, vortex-induced vibration characteristics as influenced by rainfall were obtained. Experimental results show that the wind speed when oscillation starts and the lock-in wind speed region for a slotted section model is not affected by different rainfall intensities, but the maximum amplitudes of vortex-excited resonance do have some differences. The stochastic vibration time histories for a closed section model do show effects due to different rainfall intensities, and that amplitude of vibration increases with wind speed. The closed model has the better performance in resisting vortex-induced vibration than the slotted model. The displacement amplitude under the simultaneous actions of wind and rain is bigger than the displacement amplitude under purely wind loads, the greatest increase being 25%. When rainfall intensity is light, raindrops remain attached to the surface of the structures, without bouncing and splashing. When the rainfall intensity reaches a specific value, bouncing and splashing of the raindrops can be seen.