The vehicle-track-bridge(VTB)element was used to investigate how a high-speed railway bridge reacted when it was subjected to near-fault directivity pulse-like ground motions.Based on the PEER NAG Strong Ground Motion...The vehicle-track-bridge(VTB)element was used to investigate how a high-speed railway bridge reacted when it was subjected to near-fault directivity pulse-like ground motions.Based on the PEER NAG Strong Ground Motion Database,the spatial analysis model of a vehicle-bridge system was developed,the VTB element was derived to simulate the interaction of train and bridge,and the elasto-plastic seismic responses of the bridge were calculated.The calculation results show that girder and pier top displacement,and bending moment of the pier base increase subjected to near-fault directivity pulse-like ground motion compared to far-field earthquakes,and the greater deformation responses in near-fault shaking are associated with fewer reversed cycles of loading.The hysteretic characteristics of the pier subjected to a near-fault directivity pulse-like earthquake should be explicitly expressed as the bending moment-rotation relationship of the pier base,which is characterized by the centrally strengthened hysteretic cycles at some point of the loading time-history curve.The results show that there is an amplification of the vertical deflection in the girder's mid-span owing to the high vertical ground motion.In light of these findings,the effect of the vertical ground motion should be used to adjust the unconservative amplification constant 2/3 of the vertical-to-horizontal peak ground motion ratio in the seismic design of bridge.展开更多
In order to improve the yaw stability of the vehicle with active front steering system, an adaptive PID-type fuzzy control scheme is designed to make the yaw rate tracking the desired values as close as possible. A 2-...In order to improve the yaw stability of the vehicle with active front steering system, an adaptive PID-type fuzzy control scheme is designed to make the yaw rate tracking the desired values as close as possible. A 2-DOF vehicle model with active front steering is built firstly, and then the fuzzy PID controller is designed in detail. The simulation investigations of the yaw stability with different steering ma- neuvers are performed. The simulation results show the effectiveness of the fuzzy PID controller for improving the vehicle＇s yaw stability.展开更多
The dynamics of a supersonic missile with a deflectable nose are studied. To describe the effects of nose deflection on the dynamic model, theorems of momentum and angular momentum are adopted to develop the translati...The dynamics of a supersonic missile with a deflectable nose are studied. To describe the effects of nose deflection on the dynamic model, theorems of momentum and angular momentum are adopted to develop the translational equation and rotation equation, respectively. Because the exact model is complex, it is simplified. The simplified model suggests that the main influence of nose deflection on the dynamic model is due to the product of the time derivatives of the azimuth angle and the elevation angle, which makes the dynamic model an impulsive differential system. Considering the aerodynamic characteristics a numerical simulation is sufficient to show the open-loop characteristics of the missile.展开更多
基金Project(2013CB036203)supported by the National Basic Research Program of ChinaProject(2013M530022)supported by China Postdoctoral Science Foundation+4 种基金Project(2013-K5-31)supported by Science and Technology Plan of Ministry of Housing and Urban-Rural Development of ChinaProject supported by High-level Scientific Research Foundation for the Introduction of Talent of Yangzhou University,ChinaProject supported by the Open Fund of the National Engineering Laboratory for High Speed Railway Construction,ChinaProject(IRT1296)supported by the Program for Changjiang Scholars and Innovative Research Team in University,ChinaProject(50908236)supported by the National Natural Science Foundation of China
文摘The vehicle-track-bridge(VTB)element was used to investigate how a high-speed railway bridge reacted when it was subjected to near-fault directivity pulse-like ground motions.Based on the PEER NAG Strong Ground Motion Database,the spatial analysis model of a vehicle-bridge system was developed,the VTB element was derived to simulate the interaction of train and bridge,and the elasto-plastic seismic responses of the bridge were calculated.The calculation results show that girder and pier top displacement,and bending moment of the pier base increase subjected to near-fault directivity pulse-like ground motion compared to far-field earthquakes,and the greater deformation responses in near-fault shaking are associated with fewer reversed cycles of loading.The hysteretic characteristics of the pier subjected to a near-fault directivity pulse-like earthquake should be explicitly expressed as the bending moment-rotation relationship of the pier base,which is characterized by the centrally strengthened hysteretic cycles at some point of the loading time-history curve.The results show that there is an amplification of the vertical deflection in the girder's mid-span owing to the high vertical ground motion.In light of these findings,the effect of the vertical ground motion should be used to adjust the unconservative amplification constant 2/3 of the vertical-to-horizontal peak ground motion ratio in the seismic design of bridge.
基金Supported by the National Natural Science Foundation of China （No.50705008）
文摘In order to improve the yaw stability of the vehicle with active front steering system, an adaptive PID-type fuzzy control scheme is designed to make the yaw rate tracking the desired values as close as possible. A 2-DOF vehicle model with active front steering is built firstly, and then the fuzzy PID controller is designed in detail. The simulation investigations of the yaw stability with different steering ma- neuvers are performed. The simulation results show the effectiveness of the fuzzy PID controller for improving the vehicle＇s yaw stability.
文摘The dynamics of a supersonic missile with a deflectable nose are studied. To describe the effects of nose deflection on the dynamic model, theorems of momentum and angular momentum are adopted to develop the translational equation and rotation equation, respectively. Because the exact model is complex, it is simplified. The simplified model suggests that the main influence of nose deflection on the dynamic model is due to the product of the time derivatives of the azimuth angle and the elevation angle, which makes the dynamic model an impulsive differential system. Considering the aerodynamic characteristics a numerical simulation is sufficient to show the open-loop characteristics of the missile.
