The Research Of Vehicle’s Effect To Aerodynamic Coefficient And Bridge Wind-induced Vibration

As the economic improving,the people have the higher requirements to the convenience of transportation,so the design and construction of bridges growing flexible and large span,and the cross-canyon,cross-river,cross-sea bridges becoming more than before.For the decrease of stiffness and damping value of bridge,its more and more sensitive to the wind and vehicle vibration.So it’s necessary to study the vehicle’s effect on bridge wind-excited vibration in different traffic flow.Taking the NFSC of wind-vehicle-bridge coupling system as the engineering background,and studying the vehicle’s effect on bridge wind-excited vibration in a wind tunnel lab in HUNAN University.Here is the major contents studied.1.At present, the interaction of aerodynamic forces between the road vehicles and bridge is ignored in most previous studies, especially for the influence of vehicles on aerodynamic derivatives of bridges. In the present study, for considering the effect of operating vehicles on the bridge, the forced vibration device was adopted to measure the aerodynamic derivatives of the bridge under different traffic flow in a wind tunnel. The influence of vehicles of different traffic flow under different wind attack angle on aerodynamic derivatives of the bridge, the percentage of the effect of vehicles on the derivatives and the variations of aerodynamic derivatives with the reduced velocity were investigated based on the experimental results. The measured results showed that the influence of vehicles on aerodynamic derivatives of the bridge can not be ignored. The degree of the effect of vehicles of different traffic flow under different wind attack angle on derivatives of the bridge and the variations of aerodynamic derivatives were different.2.The structure’s vortex-excited vibration is one of the most common phenomenon in wind-induced vibration,it happened at a lower wind speed,and it’s sensitive to the change of structure’s aerodynamic configuration.When vehicles driving on the bridge,it will be change the shape of bridge section.In order to consider the vehicle’s effect on bridge vortex-excited vibration on the real bridge.We had a wind tunnel test that based on free hanging segment model test system,to study the vehicle’s effect on bridge vortex-excited vibration in different traffic flow.Then we discussed how the vehicles affect the bridge vortex-excited vibration.The conclusion indicates that the vehicles are good at restraining the bridge vortex-induced vibration in different traffic flow and we do not necessary to consider the vehicles effect on vortex-excited vibration on a real bridge.3.Pressure measuring method is used to test the bridge aerodynamic coefficients with wind attack angle under different flow traffic conditions. The influence of vehicles on the bridge aerodynamic coefficients and local pressure of the bridge under different traffic flow conditions is investigated. Results show that under traffic jams condition, the influence on aerodynamic coefficients is greatest, which decreases drag coefficient and moment coefficient significantly and increases lift coefficient. In the wind-vehicle-bridge coupling systems, the pressure at windward side of the top surface of the bridge changes from positive to negative intensively.