It is necessary to study how vehicles influence the vortex-excited resonance of vehicle-bridge systems,because lock-in wind speed is low and vortex-excited resonance is sensitive to any change in the main girder secti...It is necessary to study how vehicles influence the vortex-excited resonance of vehicle-bridge systems,because lock-in wind speed is low and vortex-excited resonance is sensitive to any change in the main girder sections.Based on the Shanghai Bridge over the Yangtse River,the vortex-excited resonance of a 1∶60 scale sectional model was tested in a TJ-1wind tunnel,with or without vehicles at the attack angle of 0°,+3 and–3°,respectively.The conversion relationships between the resonant amplitudes of the sectional model and that of the prototype bridge were also established by mode shape correction.The result indicates that:1)for the bridge with vehicles,the vertical vortex-excited resonance is accompanied by torsion vibration with the same frequency,and vice versa,2)the amplitude of vortex-excited resonance of the bridge with vehicles is much larger than that of the bridge without vehicles,and 3)the lock-in wind speed of the vortex-excited resonance becomes smaller due to the disturbance of vehicles.It is obvious that vehicles bring about changes in the aerodynamic shape of the main girder.Therefore,the influence of vehicles on vortex-excited resonance performance of vehicle-bridge systems,in terms of both amplitude and mode,should not be ignored.展开更多
多主跨悬索桥颤振节段模型风洞试验存在模态匹配问题,为了明确该类试验如何匹配竖弯模态与扭转模态以及哪种弯扭模态组合的颤振临界风速最低,以马鞍山大桥为工程背景,根据模态相似性匹配出3种弯扭模态组合,在节段模型风洞试验中测试了...多主跨悬索桥颤振节段模型风洞试验存在模态匹配问题,为了明确该类试验如何匹配竖弯模态与扭转模态以及哪种弯扭模态组合的颤振临界风速最低,以马鞍山大桥为工程背景,根据模态相似性匹配出3种弯扭模态组合,在节段模型风洞试验中测试了各组合的颤振临界风速,并对结果进行比较分析.结果表明:相同攻角下,一阶反对称竖弯与一阶反对称扭转模态组合的颤振临界风速最低,因此该组合是双主跨悬索桥二维颤振的控制组合;相同攻角下,一阶对称竖弯与一阶对称扭转模态组合的颤振临界风速略高于一阶反对称竖弯与一阶对称扭转模态组合的颤振临界风速;古典耦合颤振的Van der Put公式和Selberg公式能够预测各组合的颤振临界风速相对大小关系,但不能准确预测颤振临界风速数值.展开更多
Self-excited oscillation in a collapsible tube is an important phenomenon in physiology. An experimental approach on self-excited oscillation in a thin-walled collapsi- ble tube is developed by using a high transmitta...Self-excited oscillation in a collapsible tube is an important phenomenon in physiology. An experimental approach on self-excited oscillation in a thin-walled collapsi- ble tube is developed by using a high transmittance and low Young＇s modulus silicone rubber tube. The elastic tube is manufactured by the method of centrifugal casting in our laboratory. An optical method for recording the evolution of the cross-sectional areas at a certain position along the longitudinal direction of the tube is developed based on the technology of refractive index matching. With the transparent tube, the tube law is measured under the static no-flow condition. The cross section at the middle position of the tube transfers from a quasi-circular configuration to an ellipse, and then to a dumbell-shape as the chamber pressure is increased. During the self-excited oscillation, two periodic self-excited oscillating states and one transitional oscillating state are identified. They all belong to the LU mode. These different oscillating states are related to the initial cross-sectional shape of the tube caused by the difference of the downstream transmural pressure.展开更多
文摘It is necessary to study how vehicles influence the vortex-excited resonance of vehicle-bridge systems,because lock-in wind speed is low and vortex-excited resonance is sensitive to any change in the main girder sections.Based on the Shanghai Bridge over the Yangtse River,the vortex-excited resonance of a 1∶60 scale sectional model was tested in a TJ-1wind tunnel,with or without vehicles at the attack angle of 0°,+3 and–3°,respectively.The conversion relationships between the resonant amplitudes of the sectional model and that of the prototype bridge were also established by mode shape correction.The result indicates that:1)for the bridge with vehicles,the vertical vortex-excited resonance is accompanied by torsion vibration with the same frequency,and vice versa,2)the amplitude of vortex-excited resonance of the bridge with vehicles is much larger than that of the bridge without vehicles,and 3)the lock-in wind speed of the vortex-excited resonance becomes smaller due to the disturbance of vehicles.It is obvious that vehicles bring about changes in the aerodynamic shape of the main girder.Therefore,the influence of vehicles on vortex-excited resonance performance of vehicle-bridge systems,in terms of both amplitude and mode,should not be ignored.
文摘多主跨悬索桥颤振节段模型风洞试验存在模态匹配问题,为了明确该类试验如何匹配竖弯模态与扭转模态以及哪种弯扭模态组合的颤振临界风速最低,以马鞍山大桥为工程背景,根据模态相似性匹配出3种弯扭模态组合,在节段模型风洞试验中测试了各组合的颤振临界风速,并对结果进行比较分析.结果表明:相同攻角下,一阶反对称竖弯与一阶反对称扭转模态组合的颤振临界风速最低,因此该组合是双主跨悬索桥二维颤振的控制组合;相同攻角下,一阶对称竖弯与一阶对称扭转模态组合的颤振临界风速略高于一阶反对称竖弯与一阶对称扭转模态组合的颤振临界风速;古典耦合颤振的Van der Put公式和Selberg公式能够预测各组合的颤振临界风速相对大小关系,但不能准确预测颤振临界风速数值.
基金support from the National Nature Science Foundation of China (Grants 11372305 and 11002138)K.C. Wong Education Foundation for a Royal Society K.C. Wong Postdoctoral Fellowship
文摘Self-excited oscillation in a collapsible tube is an important phenomenon in physiology. An experimental approach on self-excited oscillation in a thin-walled collapsi- ble tube is developed by using a high transmittance and low Young＇s modulus silicone rubber tube. The elastic tube is manufactured by the method of centrifugal casting in our laboratory. An optical method for recording the evolution of the cross-sectional areas at a certain position along the longitudinal direction of the tube is developed based on the technology of refractive index matching. With the transparent tube, the tube law is measured under the static no-flow condition. The cross section at the middle position of the tube transfers from a quasi-circular configuration to an ellipse, and then to a dumbell-shape as the chamber pressure is increased. During the self-excited oscillation, two periodic self-excited oscillating states and one transitional oscillating state are identified. They all belong to the LU mode. These different oscillating states are related to the initial cross-sectional shape of the tube caused by the difference of the downstream transmural pressure.
