Dynamic Analyses on Railway Track Reinforcement with Short Soil-Binder Columns
André Francisco, Laboratório Nacional de Engenharia Civil (LNEC), Transportation DepartmentShow Abstract
André Paixão, Laboratório Nacional de Engenharia Civil (LNEC)
José N. Varandas, Universidade Nova de Lisboa
Eduardo Fortunato, Laboratório Nacional de Engenharia Civil (LNEC), Transportation Department
The authors present a numerical study on railway track subgrade reinforcement using short soil-binder columns through injection, below the ballast layer. A 3D FEM program developed in MATLAB that considers the dynamic train–track interaction and the non-linear elastic behaviour of the ballast is used to study the response of the train–track–substructure system and assess stresses in the subgrade. Results suggest that reinforcements have limited impact on the train–track interaction and reduce deviatoric stresses between columns, at the top of the foundation. This method may be particularly relevant in the rehabilitation of old single railway tracks.
Dynamic Response Verification of Existing Bridges Under the Passage of Modern Railway Traffic
Chiara Rosignoli, WSPShow Abstract
Railway traffic changes in time. The industry pushes for faster travel speeds; obsolete trains are replaced and cars are added or removed. Existing lines are adapted to new traffic and statically verified per current code requirements but often changes in dynamic response are neglected. Investigation of dynamic train-bridge interaction is standard practice in high speed railway (HSR) bridge design but is rarely used for retrofitting existing structures or optimizing design of new slow-traffic railway bridges. Limiting deck accelerations is critical for reducing the amount of maintenance bridges will need in their lifetime and for ensuring passenger comfort and safety. For ballasted tracks, excessive deck acceleration may cause destabilization of ballast, leading to risk of derailment. Train induced deck accelerations are usually determined performing time consuming finite element analysis. The use of aggressivity functions is common practice for HSR design, allowing to analytically determine deck accelerations of compact section simple spans and critical speeds of each train. It can be used for final design or avoiding trial-and-error approach to dynamic analysis. The present paper describes the theory behind Fourier-series-based aggressivity functions and their applicability for checking existing slow traffic railroad bridges to modern life traffic demand. The analysis is implemented in a user-friendly spreadsheet, quickly adjustable for different bridges, trains and projects. This method can be used to easily know the maximum allowable lane speed for specific train configurations or a project specific impact factor. It can determine if over speeding could be cause of derailment in forensic analysis.
Temperature Field Analysis of Slab Track-Subgrade Structure Based on Local Meteorological Data
Rongshan Yang, Southwest Jiaotong UniversityShow Abstract
Weixin Kang, Southwest Jiaotong University
Meng Hu, Southwest Jiaotong University
Jiali Li, China Design Group Co., Ltd.
Xueyi Liu, Southwest Jiaotong University
Shihao Cao, Henan University of Technology
Predicting the temperature distribution of slab track becomes quite complex and even non-trivial due to the influence of atmospheric environment and ground condition. On the basis of thermodynamics principle, this study develops an analytical solution for predicting the transient evolution of vertical temperature distribution along the centerline of the slab track integrating with subgrade structure. Emphasis is placed on investigating the influence depth of soil temperature, leading to determination of a reasonable depth at which the bottom boundary conditions are applied for the analytical solution. To validate the proposed analytical solution, a three-dimensional numerical simulation is performed for calculating the temporal evolution of the track temperature distribution. Using the five days’ meteorological data of Chengdu in China to be the boundary conditions at external surfaces of a bi-block track structure, the evolution of temperature profile of the track-embankment whole structure is analyzed by means of the developed analytical solution and the 3D FE model. Finally, a comparison is made between the results obtained from the analytical and numerical prediction and field monitoring. Results show that only based on local meteorological data, the simple analytical solution is capable of accurately predicting the temperature field of the slab track over embankments despite of neglecting the effects of rails, fastenings, and sleepers. In addition, they demonstrate that there exists a transverse temperature gradient within the concrete slab and the supporting bed, which is essentially the same as the temperature gradient along the vertical direction. In consequence, the closer the locations towards the track edges, the lower the maximum positive temperature gradient in the vertical direction through these locations while the deeper the influence depth is.
Preliminary Development of a Mechanical Empirical-Based Wearing Model for the Conductor Rail in a Medium Capacity Transit System
Shih-Hsien Yang, National Cheng Kung UniversityShow Abstract
Fredrick Wahyu Christianto, National Cheng Kung University
In the Mass Rapid Transit (MRT) system, the conductor rail system, under cyclic loadings, there will be wear on the conductor rail and wear plate over time. Timely maintenance and replacement (M&R) of the parts in the conductor rail system is necessary to ensure the safety and availability of the MRT system. Track management system (TMS) is usually adopted to facilitate the track operation. One of the key component of the TMS is the performance model of the track that predicts the deterioration behavior of the track component. Therefore, the main objective of this study is to perform a preliminary study for developing an ME-based wear model for conductor rails and wear plates intended to predict their wear deterioration. In this study, the collected data were used to develop a mechanical-empirical model of the wear behavior of the conductor rail system in the Medium Capacity Transit System (MCTS). The Archard wear model was employed in this study to calculate the theoretical wear value under service conditions. The results were used in conjunction with wear inspection data in the field to develop an empirical prediction model with which to estimate the load to failure (Nf) using a linear regression. The result of the ME-based wear model for the wear plate, the percent errors were higher in the wear depth of 1 and 2 models. For the conductor rail, the percent errors were irrelevant to wear level and were stable below 16%.