Shielding Effect By Bridge Tower Of Single-Level Rail-Cum-Road Bridge On Wind Environment Around Bridge Deck And Aerodynamic Parameters Of Train

To explore the influence of shielding effect by bridge tower of single-level rail-cum-road bridge on wind environment around the bridge deck and aerodynamic parameters of train,The computational fluid dynamics was employed,By analyzing the distribution of vortex,wind velocity factor,wind velocity factor variance and wind velocity reduction factor at different heights of each lane on bridge deck around the tower,The flow field distribution at different heights of each lane on bridge deck around the tower was studied when the bridge deck without auxiliary structure,The influence of Reynolds number and the bridge deck arrange railings and wind barriers on the wind environment of deck around the tower was compared.Based on three-vehicle model,The influence of the line position,wind velocity,train speed and wind azimuth on the aerodynamic coefficient of the middle vehicle when the train passes by the bridge tower without auxiliary structure was investigated.The critical overturning wind velocity of the middle vehicle was calculated when the train passes by the bridge tower.The effects of the bridge deck arrange railings and wind barriers on the aerodynamic coefficient and overturning stability of the middle vehicle when the train passes by the bridge tower are compared.The results show that:1)The wind velocity reduction and wind velocity fluctuation of the windward side bridge deck in roadway around the bridge tower are small.The wind velocity of the railway bridge deck and the road bridge deck on the leeward side is accelerated to a certain extent on the outside of the bridge tower,and the wind velocity fluctuation increased,the wind velocity and wind velocity fluctuation behind the tower column are significantly reduced.The wind velocity and wind velocity fluctuation of the railway bridge deck between two tower columns are improved.At the lower height outside the bridge tower from the bridge deck,due to the existence of the vortex,the wind velocity at the vortex position has a sudden drop area,and the wind velocity fluctuation at the outside of the vortex has a sudden increase area.With the increase of the height from the bridge deck,the vortex disappears.The wind velocity and wind velocity fluctuation of the leeward side of the roadway bridge deck between the two tower columns still greatly reduced,with the increase of the height from the bridge deck,the wind velocity on the outside of the bridge tower increases,while the wind velocity reduction behind the tower column and between the two tower columns increases.2)The Reynolds number has little effect on the wind velocity and wind velocity fluctuation in bridge deck around the tower.3)When the train passes by the bridge tower,the aerodynamic coefficient has a sudden change.When the train runs on the windward side line,the sudden change of the lateral force coefficient and the lift coefficient is larger than that on the leeward side line,and the sudden change of the moment coefficient is smaller than that on the leeward side line.With the increase of train speed,the influence range of the bridge tower on the lateral force coefficient and moment coefficient of the train tends to increase,and the sudden change of the lift coefficient tends to slow down.With the increase of wind velocity,the sudden change of the lateral force coefficient and the moment coefficient of the train tends to slow down,and the lift coefficient is opposite.At the wind azimuth of 0～20°,the sudden change of the lateral force coefficient and moment coefficient of the train is the largest when the wind azimuth is10°,and the influence position of the bridge tower on the train lift coefficient shifts with the change of the wind azimuth.4)The critical overturning wind velocity of train runs on the windward side line is lower than that on the leeward side line when the train passes by the bridge tower.The overturning stability of the train passes by the bridge tower of both lines meets the requirements.5)After bridge deck arrange railings and wind barriers,the changes of wind velocity and wind velocity fluctuation on the bridge deck around the tower is more slowly.The sudden change of aerodynamic coefficient is slow down.And the overturning stability of the train is improved when the train passes by the bridge tower.