Quantification of Lateral Forces in Concrete Crosstie Fastening Systems

Transcription

1 in Concrete Crosstie Fastening Systems Transportation Research Board 94 th Annual Meeting Washington D.C. 13 January 21 Brent Williams, Donovan Holder, Marcus Dersch, Riley Edwards, and Christopher Barkan

2 Slide 2 Outline Research Motivation Defining Lateral Load Path and Fastening System Field Experimental Setup TTC Dynamic Transfer of Lateral Loads Laboratory Experimental Setup - TLS Demand on Shoulder Varying Static Vertical Load Quantifying Lateral Load Distribution Varying Friction Conclusions Future Work

3 Current Performance Challenges Relating to Lateral Loads Lateral forces through fastening system is believed to be a contributor to shoulder and insulator deterioration Slide 3

4 Slide 4 Purpose of Lateral Force Measurement Quantify lateral loading conditions to aid in the mechanistic design of fastening systems Understand demands on fastening system components under loading conditions known to generate failures Gain understanding of the lateral load path by: Quantifying forces and stresses acting on the insulator and shoulder Quantifying the distribution of lateral forces in fastening system e.g. Bearing on shoulder, frictional resistance from rail pad assembly or clip, etc. Understanding the causes of variation on lateral load distribution among adjacent crossties

5 Slide Defining the Lateral Load Path Vertical Wheel Load Lateral Wheel Load Rail Bearing Forces Frictional Forces Clip Insulator Rail Pad Assembly Shoulder Concrete Crosstie

6 Slide 6 Measurement Technology Lateral Load Evaluation Device (LLED) Replaces original face of cast shoulder Maintains original fastening system geometry Designed as a beam in four-point bending Bending strain is resolved into force through calibration curves generated in the lab

7 Slide 7 Field Experimental Setup - TTC Objective: Analyze the distribution of forces through the fastening system and impact on the relative displacement of components Location: Transportation Technology Center (TTC) in Pueblo, CO Railroad Test Track (RTT): tangent section High Tonnage Loop (HTL): curved section Instrumentation: - Strain gauges - LLED - Potentiometers Transportation Technology Center (TTC) HT L RTT High Tonnage Loop (HTL)

8 Slide 8 Dynamic Loading Environment Customized freight train Three six-axle locomotives Ten freight cars with 263k, 286k, and 31k cars Speeds of 2 mph,1 mph, 3 mph, 4 mph, and 4 mph FAST train Speeds of 2-4 mph Tested on HTL (curved section)

9 Slide 9 Dynamic Transfer of Lateral Loads: Freight Train - Measured at Shoulder Peak LLED and lateral wheel loads from each passing freight wheel Dynamic loads are applied at much higher rates than static LLED Force (lbf) 8, 7, 6,, 4, 3, Higher bearing forces 2, may be caused by 1, lowered COFs Rail Seat E (High Rail) Rail Seat U (Low Rail) Lateral Wheel Load (Kips)

10 Slide 1 Dynamic Transfer of Lateral Loads: Freight Train - Measured at Shoulder Absolute LLED values recorded throughout each pass of the FAST train Data recorded during varying speeds: 2 4 mph Large variability in forces on the shoulder at higher lateral wheel loads 2 4 MPH

11 Slide 11 Lab Experimental Setup Track Loading System (TLS) L input L reaction Track Loading System (TLS) allows for testing of track infrastructure similar to field conditions. L input is obtained from strain gauges attached to the rail L reaction is obtained from LLED devices installed in the shoulder of crossties being tested

12 Lateral Load Path and Fastening System Setup Slide 12 Vertical Wheel Load L input Bearing Forces Frictional Forces L reaction Primary lab research objective is to study the frictional force between the rail pad and the rail seat. Low friction layer made of BoPET used to investigate the importance of friction in lateral force distribution through track infrastructure

13 Force (kips) Force (kn) Force (kips) Force (kn) Slide 13 Quantifying Lateral Load Distribution kips 4 kips 8 No Low Friction Layer Installed 4 8 Low Friction Layer Installed

14 Force (kips) Force (kn) Force (kips) Force (kn) Slide 14 Quantifying Lateral Load Distribution 4 kips 4 kips 8 No Low Friction Layer Installed 4 8 Low Friction Layer Installed

15 Force (kips) Force (kn) Force (kips) Force (kn) Slide 1 Quantifying Lateral Load Distribution 1 kips 4 kips 8 No Low Friction Layer Installed 4 8 Low Friction Layer Installed

16 Force (kips) Force (kn) Force (kips) Force (kn) Slide 16 Quantifying Lateral Load Distribution 18 kips 4 kips 8 No Low Friction Layer Installed 4 8 Low Friction Layer Installed

17 % of Lateral Wheel Load Resisted at Shoulder Slide 17 Quantifying Lateral Load Distribution 6% No Low Friction Layer % Low Friction Layer 4% 3% 2% 1% 2 kips 4 kips % B A C Crosstie

18 L reaction (kips) Slide 18 Contribution of Friction in Properly Supported Crosstie V=3kips V=3kips V=4kips V=4kips Low Friction Layer Installed kips L input (kips) No Low Friction Layer Installed

19 L reaction (kips) Quantification of Lateral Forces Contribution of Friction in Poorly Supported Crosstie Slide V=3kips V=3kips V=4kips V=4kips Low Friction Layer Installed L input (kips) 1.8 kips No Low Friction Layer Installed

20 Slide 2 Global Distribution of Lateral Forces in Properly Supported Crosstie No Low Friction Layer Installed Low Friction Layer Installed L reaction /L input B A C Crosstie

21 Slide 21 Global Distribution of Lateral Forces in Poorly Supported Crosstie No Low Friction Layer Installed Low Friction Layer Installed L reaction /L input B A C Crosstie

22 Slide 22 Conclusions A higher percentage of lateral wheel loads is transferred to the fastening system under dynamic loading than static loading Increasing vertical load increases the lateral bearing force against the shoulder Altering the lateral friction between rail pad and rail seat increases the magnitude of lateral bearing force at the shoulder Implications on the design of fastening systems to better distribute lateral loads Support conditions influence the magnitude of lateral load transfer into the shoulder

23 Slide 23 Future Work Focused experimentation to better understand lateral forces through the fastening system under varying support conditions Investigating the lateral load distribution through the track structure with missing fastening system components Comparison of the lateral load performance between the spring clip (Safelok I) and the Skl style (tension clamp) fastening system

24 Slide 24 Acknowledgements Funding for this research has been provided by: Federal Railroad Administration (FRA) Association of American Railroads (AAR) Technology Outreach Program 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 For assistance with research and lab work Brent Wiliams, Donovan Holder, UIUC Machine Shop FRA Tie and Fastener BAA Industry Partners:

25 Slide 2 Contact Information Marcus Dersch Senior Research Engineer mdersch2@illinois.edu Donovan Holder Graduate Research Assistant holder2@illinois.edu Riley Edwards Senior Lecturer and Research Scientist jedward2@illinois.edu

26 Slide 26 Appendix

27 Slide 27 TLS Instrumentation Map (Wei 214) Lateral Load Evaluation Device (LLED) Lateral and Rail Seat Load Circuits Vertical Load Circuit Lateral Load Circuit Rail Displacement (Base Vert. Gauge, Base Lat., Web Lat.) Rail Displacement (Base Vert. Field) Embedment Gauges Lateral Crosstie Displacement Crosstie Surface Strains Vertical Crosstie Displacement

28 Shoulder Lateral Reaction (kips) Shoulder Lateral Reaction (kn) Slide 28 Lateral Stiffness..1 Rail Base Displacment (mm) Rail Base Displacment (in)

29 Slide 29 TLS Track Installation After Before Clip Clip Installation Gap Between Rail & Crosstie Poorly Supported Crosstie