Effect of Lateral Load on Rail Seat Pressure Distributions

Transcription

1 Slide 1 Effect of Lateral Load on Rail Seat Pressure Distributions Joint Rail Conference Colorado Springs, CO 3 April 2014 Matthew J. Greve, J. Riley Edwards, Marcus S. Dersch, Ryan G. Kernes, and Christopher P.L. Barkan

2 Slide 2 Outline RSD Background Pressure Distribution Relation to RSD Equipment Overview Field Data Analysis Load Distribution Progression Contact Areas vs. L/V Rail Seat Load Sensitivity Pressure Comparison Developing a New Design Metric Conclusions Future Work

3 FRA Tie and Fastener Research Program Overall Project Deliverables Slide 3 Mechanistic Design Framework Literature Review Load Path Analysis International Standards Current Industry Practices AREMA Chapter 30 I TRACK Statistical Analysis from FEM Free Body Diagram Analysis Probabilistic Loading Finite Element Model Laboratory Experimentation Field Experimentation Parametric Analyses

4 Slide 4 Current Objectives of Experimentation with Matrix Based Tactile Surface Sensors (MBTSS) Compare pressure distribution on rail seats: Under various loading scenarios Under various rail seat support conditions Under various stages of rail seat wear Develop design metric for mechanistic evaluation of rail seat load distribution

5 Slide 5 Rail Seat Deterioration (RSD) Background Rail Seat Deterioration (RSD) is the degradation of concrete directly underneath the rail pad, resulting in track geometry problems Surveys conducted by UIUC report that North American Class I Railroads and other railway infrastructure experts ranked RSD as one of the most critical problems associated with concrete crosstie and fastening system performance Potential RSD mechanisms as determined through research at UIUC: - Abrasion - Crushing - Freeze-thaw - Hydraulic pressure cracking - Hydro-abrasive erosion Original Rail Seat Surface

6 Slide 6 Equipment Preparation and Protection Sensors trimmed to fit rail seat BoPET and PTFE layered on each side of sensor to protect from shear and puncture damage Plastic sleeves and plastic bags to protect sensor tabs and handles from puncture and debris Rail MBTSS Setup Pad/Abrasion Plate BoPET: PTFE: Sensor: PTFE: BoPET: Cast-in Shoulders Concrete Crosstie Gauge Field Plan View of Sensor and Protective Layers

7 Field Experiment Program Objective: Analyze the distribution of forces through the fastening system and impact on components relative displacements Location: Transportation Technology Center (TTC) in Pueblo, CO Railroad Test Track (RTT): tangent section with Safelok I fasteners Instrumentation: - MBTSS deployed to capture wheel load distribution, behavior of rail seats on the same crosstie, and effect of crosstie support conditions - Potentiometers to capture crosstie vertical displacement Loading: Track Loading Vehicle (TLV) used to apply static loads to the track structure Modified railcar with instrumented wheelset on hydraulic actuators Slide 7 Transportation Technology Center (TTC) RTT Track Loading Vehicle (TLV)

8 May 2013 Field Instrumentation Slide A B C E G H I D F P Q R S T U V X W Y Z MBTSS Crosstie Vertical Displacement Rods Rail Displacement Fixture Rail Longitudinal Displacement/Strains Pad Assembly Longitudinal Displacement Pad Assembly Lateral Displacement Vertical Web Strains Vertical and Lateral Circuits Shoulder Beam Insert (Lateral Force) Crosstie Surface Strains Embedment Gages, Vertical Circuit, Clip Strains

9 Slide 9 Unloaded Increasing Pressure Rail Seat Load Concentration 40 kips A 0 kips % Initial Contact Area 3: 100% 11: 100% P

10 Slide 10 Unloaded Increasing Pressure Rail Seat Load Concentration 40 kips A 4 kips % Initial Contact Area 3: 101% 11: 100% P

11 Slide 11 Unloaded Increasing Pressure Rail Seat Load Concentration 40 kips A 8 kips % Initial Contact Area 3: 101% 11: 101% P

12 Slide 12 Unloaded Increasing Pressure Rail Seat Load Concentration 40 kips A 12 kips % Initial Contact Area 3: 101% 11: 101% P

13 Slide 13 Unloaded Increasing Pressure Rail Seat Load Concentration 40 kips A 16 kips % Initial Contact Area 3: 84% 11: 79% P

14 Slide 14 Unloaded Increasing Pressure Rail Seat Load Concentration 40 kips A 20 kips % Initial Contact Area 3: 62% 11: 58% P

15 Slide 15 Unloaded Increasing Pressure Nonuniform Rail Seat Load Response 40 kips A 20 kips % Initial Contact Area 1: N/A 9: 83% P

16 Slide 16 Unloaded Increasing Pressure Nonuniform Rail Seat Load Response 40 kips A 20 kips % Initial Contact Area 2: 68% 10: 62% P

17 Slide 17 Increasing Pressure Unloaded Nonuniform Rail Seat Load Response 40 kips A 20 kips % Initial Contact Area 3: 62% 11: 58% P

18 Slide 18 Unloaded Increasing Pressure Nonuniform Rail Seat Load Response 40 kips A 20 kips % Initial Contact Area 4: 73% 12: 69% P

19 Slide 19 Unloaded Increasing Pressure Nonuniform Rail Seat Load Response 40 kips A 20 kips % Initial Contact Area A: N/A P: 86% P

20 Percent of Initial Contact Area Slide 20 TLV Varying Lateral Load at RTT 40,000 lb (178 kn) Vertical Load P A P L/V Force Ratio

21 Percent of Initial Contact Area Slide 21 TLV Varying Lateral Load at RTT 20,000 lb (88.9 kn) Vertical Load P A P L/V Force Ratio

22 Pressure (psi) Pressure (MPa) Slide 22 Effect of L/V Force Ratio on Pressure Current design practice is to assume a uniformly distributed rail seat load, even under high L/V force ratios. Increased pressure changes abrasion characteristics Introduction of fines may concentrate load further causing local crushing 2,500 2,000 Maximum Pressure ,500 1,000 Average Pressure Uniform Pressure L/V Force Ratio (Constant 40,000 lb Vertical Load)

23 Load (lb) Load (kn) Slide 23 Concentration of Rail Seat Load 40,000 lb (178 kn) Vertical Load Distance from Field Shoulder (mm) , , , , , L/V Force Ratio Distance from Field Shoulder (in) 0.00

24 Slide 24 Definition of Rail Seat Load Index (RSLI) A quantifiable design value which describes the sensitivity of the rail seat load distribution to changes in the L/V force ratio Rail Seat Load Index (RSLI) is defined as the percent of total rail seat load imparted onto a critical region of the rail seat, defined as the area of the rail seat not more than 1 inch (25.4 mm) from the field side shoulder, normalized to a theoretical, uniform distribution. RSLI RSI = [Load in Critical Area] [Total Rail Seat Load] 1 6 = 6 [Load in Critical Area] [Total Rail Seat Load]

25 Rail Seat Load Index Slide 25 Theoretical Optimized RSLI Excessive loading on field side of rail seat Accelerated fastener component wear Increased RSD potential Optimal Design Zone Excessive loading on gauge side of rail seat Accelerated fastener component wear Increased RSD potential L/V Force Ratio

26 Rail Seat Load Index Slide 26 Effect of L/V on RSLI L/V Force Ratio Rail Seat P 9

27 Slide 27 Conclusions Rail seat load distribution is highly nonuniform, even between adjacent crossties Rail base rotation at threshold L/V force ratio can lead to significant load concentration on field side of rail seat Loss of up to 54% of initial contact area The behavior of the load distribution under increasing L/V force ratios is affected by the magnitude of vertical load Average and maximum pressure are affected by reduction of contact area 71% increase in average pressure 98% increase in maximum pressure RSLI provides a mechanistic evaluation of rail seat load sensitivity Lateral force plays a significant role in RSD mechanisms because of its effect on contact area

28 Slide 28 Future Work How did crosstie support conditions affect wheel and rail seat load distributions in the field? Can we understand the effect of crosstie support conditions by controlling undertie ballast stiffness? How are threshold L/V and vertical load related? Can we correlate load nonuniformity to RSD? How does RSLI change with fastening system wear? Can RSLI be correlated to RSD or specific RSD mechanisms?

29 Slide 29 Acknowledgements Funding for this research has been provided by the Amsted RPS / Amsted Rail, Inc. Federal Railroad Administration (FRA) Industry Partnership and support has been provided by Union Pacific Railroad BNSF Railway National Railway Passenger Corporation (Amtrak) Amsted RPS / Amsted Rail, Inc. GIC Ingeniería y Construcción Hanson Professional Services, Inc. CXT Concrete Ties, Inc., LB Foster Company TTX Company UIUC Zachary Ehlers, Doug Capuder, Marc Killion, and Timothy Prunkard FRA Tie and Fastener BAA Industry Partners:

30 Hosting 2014 International Crosstie and Fastening System Symposium Co-organized by: AREMA Committee 30 (Ties), Railway Tie Association (RTA) Three day conference with presentations, discussions, and a technical tour Focus state of the art in timber, concrete, and composite crosstie and fastening system design, performance, research, modeling, and inspection 3-5 June 2014 Sessions on UIUC campus 4 June 2014 Technical tour to UIUC Research and Innovation Laboratory (RaIL) and voestalpine Nortrak facility in Decatur, IL Strong domestic and international participation; addressing topics including: Laboratory and Field Testing Component and System Modeling Automated Inspection Technologies 2014 International Crosstie & Fastening System Symposium 3-5 June 2014 Slide 30 Rail Transportation and Engineering Center (RailTEC) University of Illinois at Urbana-Champaign (UIUC) Newmark Civil Engineering Lab 205 N. Mathews Avenue Urbana, IL 61801

31 Slide 31 Matthew Greve Graduate Research Assistant Questions & Comments