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ACKNOWLEDGMENT This work was sponsored by the Federal Transit Administration (FTA) in cooperation with the Transit Development Corporation. It was conducted through the Transit Cooperative Research Program (TCRP), which is administered by the Transportation Research Board (TRB) of the National Academies. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, Transit Development Corporation, or AOC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied activities annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individu- als interested in the development of transportation. www.TRB.org www.national-academies.org
i EXECUTIVE SUMMARY Poor vehicle dynamic performance and poor ride quality frequently occur at track locations that do not exceed track geometry or safety standards, such as curve entry or exit, special trackwork, and track misalignments that promote yaw instability or hunting. Poor ride quality may not be an indicator of unsafe operation, but it may point to an area of track or a vehicle that needs maintenance to prevent further degradation. Conversely, track geometry locations that exceed track geometry or safety standards often do not cause poor ride quality or poor vehicle performance. To optimize transit system maintenance, methods need to be developed to identify vehicle conditions and track locations that actually cause poor ride quality or vehicle performance. Track geometry measurements alone are not always an indicator of how a vehicle behaves. Predicting the vehicle dynamic response can help address the following issues: ⢠Prioritizing maintenance ⢠Identifying problem locations that do not exceed normal track geometry standards ⢠Identifying problems as they arise rather than waiting for scheduled maintenance ⢠Identifying car designs and car component wear issues that can contribute to poor vehicle performance and poor ride quality To improve and advance the current track geometry inspection practice and standards, Transportation Technology Center, Inc. (TTCI) developed a track inspection method known as performance-based track geometry (PBTG). Trained neural networks in the PBTG system relate the complex dynamic relationships that exist between vehicles and track geometry to vehicle performance. They also identify track segments that may generate unwanted vehicle responses. PBTG is now in use by three North American freight railroads and one international railroad. A transit agency can use PBTG to optimize maintenance of the track and fleet. Onboard accelerometers on the fleet and a PBTG neural network can be used to identify track locations that need work and do not require direct measurement of the track geometry. This permits monitoring of track condition between scheduled track geometry measurements. PBTG can also be used to identify cars that are beginning to deteriorate. If all cars in the fleet are equipped with PBTG accelerometers, they can be used to build a database of information for monitoring the condition of the cars and the track over time. Also, PBTG uses measured track geometry and the PBTG neural network to predict vehicle performance on existing track. This helps to identify locations in the track likely to cause poor ride quality or other issues related to vehicle performance, which is the way PBTG is currently being applied by North American freight railroads.
ii An indirect benefit of implementing the PBTG system can be making validated vehicle dynamics models available to a transit agency. The models can be used for many other purposes such as investigating dynamic performance problems, evaluating vehicle modifications, evaluating vehicle performance over proposed new track routes and alignments, and optimizing wheel and rail profile maintenance. In support of the Transit Cooperative Research Program (TCRP) D-7 research program, TTCI is conducting research to develop methods for evaluating track geometry that will account for transit system vehicle performance and passenger ride quality using a combination of PBTG and NUCARS®1 ⢠Proof of Concept: Determine if PBTG will work to predict ride quality for the transit industry modeling techniques and on-track measurements. These studies will form the basis for determining improvements in track geometry and track maintenance practices. The overall objective for the project is to demonstrate the use of PBTG techniques for improving the ride quality of transit systems. The project is being conducted with the cooperation of Dallas Area Rapid Transit (DART). Specific deliverables of this multiphased project include: ⢠Trained PBTG neural net algorithms for DART and one other transit system ⢠Methodology and recommendations for implementing PBTG techniques on other transit systems This report addresses Phase I of this work, which consisted of the following items: ⢠Ride Quality Literature Survey (Appendix) ⢠Vehicle Characterization and On-track Ride Quality Testing ⢠Track Geometry Measurements ⢠NUCARS Modeling ⢠Comparison of NUCARS simulations to on-track test results to determine whether the vehicle performance and ride quality can be linked to specific track geometry features Phase II of the project will use the NUCARS simulations and data collected on transit systems during Phase I to train PBTG neural networks and the PBTG modelâs ability to predict ride quality. Phase II tasks include (1) using the Phase I NUCARS simulations and on-track test results to train PBTG neural networks to predict ride quality and (2) identifying track locations where track geometry maintenance could improve ride quality. Phase II will also include similar on-track tests, NUCARS simulations, and PBTG analyses for another transit authority using another vehicle type. 1 NUCARS is a registered trademark of Transportation Technology Center, Inc.
iii Four ride quality standards used to evaluate passenger comfort on rail transit vehicles were reviewed in Phase 1: ⢠International Organization for Standardization (ISO) 2631 Mechanical Vibration and Shock ⢠European Standards (ENV) 12299:1999 Railway Applications ⢠International Union of Railways (UIC) 513 ⢠Sperling Index All four standards require similar measurements. Therefore, the following ride quality measurements were identified for use in this study: ⢠Tri-axial accelerometers located a. Over bogie centers (both ends of vehicle) b. On center of vehicle c. On floor in operatorâs cabin ⢠Lateral accelerometers located a. On each axle of bogie so yaw can be calculated and location of curve accurately pinpointed ⢠Roll rate gyrometer Based on the literature review, TTCI recommended that ride quality during the tests be calculated using the ISO 2631standards, because it was the most comprehensive. TTCI has often found that actual vehicle characteristics as assembled vary considerably from the published design and measured individual components. In order to ensure an accurate NUCARS model of the Dallas Area Rapid Transit (DART) Super Light Rail Vehicle (SLRV), tests were conducted to measure suspension characteristics and carbody inertial and resonance characteristics, including: ⢠Characterization of the elastic elements of the primary and secondary suspension ⢠Determination of the center of gravity of the railcar ⢠Determination of the resonance frequencies of rigid body degrees of freedom of the railcar All vehicle characterization and ride quality testing was performed on DART property located in Dallas, Texas, using a DART SLRV. DARTâs operating conditions provided a variety of track structures and a wide range of operating speeds. Track geometry measurements were taken by Holland on DART Red Line in both directions. No measurements were taken in the tunnel, because of size restrictions. The tunnel had direct fixation track, and therefore, it was assumed that track geometry measurements could be used. This research determined there is a correlation between ride quality and track geometry. Locations on the DART Red Line that had ride quality issues were identified from the ride quality test performed, as Table 1 shows.
iv Table 1. Ride Quality Issues Identified on DART Red Line Direction Stations Lateral Ride Quality Index Description Northbound Dallas Zoo to 8th 0.661 & Corinth Fairly uncomfortable Northbound Walnut Hill to Forest Lane 0.763 Fairly uncomfortable Northbound LBJ/Central to Spring Valley 0.651 Fairly uncomfortable Northbound Galatyn Park to Bush Turnpike 0.681 Fairly uncomfortable Southbound Plano Center to Bush Turnpike 0.845 Uncomfortable Southbound Spring Valley to LBJ/Central 0.640 Fairly uncomfortable Southbound Cedars to 8th 1.056 & Corinth Uncomfortable The southbound section of track between Cedars and 8th These results indicated it should be possible to identify the effect of track geometry deviations on vehicle ride quality response during Phase II of the project. However, there is still some work required to improve the vehicle model to correctly predict this response. Identifying the influence of the following factors on vehicle response is important to accurately model and determine track geometry triggers: & Corinth stations contained lateral alignment deviations with a wavelength of 94 feet, corresponding to a frequency of 1 Hertz (Hz) at the speed the train was traveling. This resulted in a vehicle yaw response of 1 Hz resulting in an âuncomfortableâ ride quality index of 1.056. Although these track geometry deviations did not exceed any safety criteria, they clearly affect passenger ride quality. To show this correlation between ride quality and track geometry, it was imperative to take track geometry measurements at the same time as ride quality measurements. ⢠Wheel/rail interface, including profile shapes and contact geometry ⢠Vehicle speed ⢠Understanding and identifying rigid body vibration modes of the vehicle
v Table of Contents 1.0 Introduction ................................................................................................................................ 1 1.1 ..... Ride Quality Literature Survey 3 1.2 ..... Vehicle Characterization and Ride Quality Testing ................................................................... 3 1.3 ..... NUCARS Modeling ................................................................................................................... 3 1.4 ..... PBTG .......................................................................................................................................... 4 2.0 Literature Survey ........................................................................................................................ 4 3.0 Vehicle Characterization and On-track Tests ............................................................................. 6 3.1 ..... Vehicle Characterization Tests ................................................................................................... 8 3.1.1 Carbody Resonance Tests ................................................................................................ 8 3.1.2 Bogie Resonance ............................................................................................................11 3.1.3 Suspension Stiffness .......................................................................................................13 3.2 ..... Track Inspection and Track Geometry Measurements ..............................................................15 3.3 ..... Ride Quality Test .......................................................................................................................19 4.0 Vehicle Characterization Data Analysis ....................................................................................21 4.1 ..... Carbody Resonance Test ...........................................................................................................21 4.2 ..... Bogie Resonance Test ...............................................................................................................24 4.3 ..... Longitudinal Stiffness Test ........................................................................................................29 4.4 ..... Lateral Stiffness Test .................................................................................................................31 4.5 ..... Vertical Stiffness Test ...............................................................................................................32 5.0 Ride Quality and Track Geometry Data Analysis......................................................................34 5.1 ..... Ride Quality Test .......................................................................................................................34 5.2 ..... Track Geometry .........................................................................................................................42 5.3 ..... Ride Quality and Track Geometry Comparison ........................................................................45 6.0 Wheel and Rail Profiles .............................................................................................................50 7.0 NUCARS Modeling ...................................................................................................................50 8.0 Conclusions ...............................................................................................................................53 8.1 ..... Ride Quality Standard Literature Review ..................................................................................53 8.2 ..... Vehicle Characterization Testing...............................................................................................53 8.3 ..... Track Geometry Measurements .................................................................................................53 8.4 ..... Ride Quality and Track Geometry Comparison ........................................................................54 9.0 What is Next: Phase II ...............................................................................................................54 Acknowledgment ...........................................................................................................................................55 Appendix Ride Quality Literature Review ..................................................................................................56
vi List of Figures Figure 1. DART Rail System Map .................................................................................................................. 6 Figure 2. DARTâs Super Light Rail Vehicle ................................................................................................... 7 Figure 3. Illustration of Measured Rigid Body Vibration Modes .................................................................... 9 Figure 4. Location of Carbody Resonance Test Instrumentation .................................................................. 10 Figure 5. Using a Crowbar to Excite Carbody Yaw Vibration Mode ............................................................ 11 Figure 6. Hammer Test and SLRV Motor Truck........................................................................................... 12 Figure 7. Accelerometer Locations for Motor Truck and Trailer Truck ....................................................... 12 Figure 8. Setup of Longitudinal Pull Test ..................................................................................................... 13 Figure 9. Wheel Load Cells ........................................................................................................................... 14 Figure 10. SLRV on Vertical Lift .................................................................................................................. 14 Figure 11a. Curve Rail Profiles High Rail ..................................................................................................... 15 Figure 11b. Curve Rail Profiles Low Rail ..................................................................................................... 16 Figure 12. Tangent Rail Profiles .................................................................................................................... 16 Figure 13. Track Geometry Issues ................................................................................................................. 17 Figure 14. Hollandâs TrackSTAR Vehicle .................................................................................................... 18 Figure 15. MCO Measurement Issue ............................................................................................................. 18 Figure 16. Required Track Geometry Information ........................................................................................ 19 Figure 17. Ride Quality Instrumentation ....................................................................................................... 20 Figure 18. Location of Ride Quality Instrumentation .................................................................................... 20 Figure 19. Raw Acceleration Data from Carbody Resonance Test ............................................................... 22 Figure 20. Lower Center Roll Rigid Body Vibration Mode .......................................................................... 23 Figure 21. Lower Center Roll Vibration Mode Frequency ............................................................................ 23 Figure 22. Traction Motor Mount Locations ................................................................................................. 25 Figure 23. Hammer Input and Resulting Output â Vertical Direction ......................................................... 26 Figure 24. Time Domain Data and Frequency Content from Hammer Test ................................................. 27 Figure 25. Decay Plot of Vertical Motor Mount Accelerations ..................................................................... 29 Figure 26. Longitudinal Displacement and Load Measurements .................................................................. 30 Figure 27. Force-Displacement Diagram and Calculated Slope .................................................................... 30 Figure 28. Primary Suspension System â Chevrons ...................................................................................... 31 Figure 29. Lateral Displacement and Load Measurements ........................................................................... 32
