System dynamics in structural strength and vibration fatigue life assessment of the swing bar for high‐speed maglev train

High‐speed maglev trains are subjected to severe dynamic loads,thus posing a failure hazard.It is necessary to account for the vehicle dynamics to improve the structural strength and fatigue life assessment approach under harsh routes and super high‐speed grades.As the most critical load‐carrying part between the vehicle body and levitation frames,the swing bar was taken as an example to demonstrate the significance of vehicle dynamics to integrate classical structural strength and fatigue life with the service conditions.A multiphysics‐coupled dynamic model of an alpha improvement scheme for an electromagnetic suspension maglev train capable of 600 km/h was established to investigate the complex dynamic loads and fatigue spectra.Using this model,the structural strength and fatigue life of the wrought swing bars were investigated.Results show only a slight effect on the structural strength and fatigue life of swing bars by the super high‐speed grades.The nonaxial bending moments caused by the uncompensated relative displacement between the vehicle body and bolsters are identified as the decisive factors.The minimum safety factor of the structural strength for wrought swing bars is 1.33,while the minimum fatigue life is 34 years.Both match the design requirements but are not conservative enough.Therefore,further verification and optimization are recommended to improve the design of swing bars.

Travel time reliability with and without the dynamic use of hard shoulder:Field assessment from a French motorway

Traffic management aims to ensure a high quality of service for most users by decreasing congestion and increasing safety. However, uncertainty regarding travel time decreases the quality of service and leads end-users to change their routes and schedules even when the average travel time is low, Indicators describing travel time reliability are being developed and should be used in the future both for the optimization and the assessment of active traffic management operation. This paper describes a managed lane experience on a motorway weaving section in France - hard shoulder running operation in rush hours. The paper is focused on travel time reliability indicators and their use for reliability assessment. It provides some discussions about the advantages and drawbacks of reliability indicators under different traffic conditions. It particularly shows the difference between using buffer times and buffer indexes. The paper also discusses the difficulty of interpreting the skew of travel time distribution for travel reliability,