Aerodynamic of Bridge Stay Cables Under Simultaneous Action of Rain and Wind – Part I: Vortex Shedding

Resumo

Simultaneous occurrences of cable vibrations under combined action of wind and rain have been observed around the world in cable-stayed bridges in the last 20 years. This mechanism has caused great concern to bridge engineers and researchers due to the large vibration amplitudes. These vibrations, which are predominantly cross-wind, were observed only under conditions of light rain and low wind speed occurring simultaneously. It was possible to determine, in experimental study, the influence of rivulets on the vortex shedding in three sectionals models. The M1 model was positioned horizontally with perpendicular wind incidence to the longitudinal axis, the M2 model was positioned horizontally with oblique wind to the longitudinal axis and the M3 model is a typical, cable of cable-stayed bridges. For the M3 model, the vortex shedding intensity increases for all rivulets positions. The greater intensity occurred when the upper and lower rivulets were at 50° and 110°, respectively. For all models with rivulets, the vortex shedding is stronger in turbulent flow. This shows, therefore, the effects of the axial vortex. For Re < 1.2 x 105 the lower rivulet has no influence on the flow. However, for Re > 1.2 x 105 the lower rivulets affect significantly the flow around the cylinder. For the inclined model the lower rivulet has no influence on the flow for all Re range.