Measuring and Modeling Differential Movement at Railroad Track Transitions

Transcription

1 William W. Hay Railroad Engineering Seminar Measuring and Modeling Differential Movement at Railroad Track Transitions Timothy Stark Professor University of Illinois at Urbana-Champaign Date: Friday, January 30, 2015 Time: Seminar Begins 12:20 Sponsored by Location: Newmark Lab, Yeh Center, Room 2311 University of Illinois at Urbana-Champaign

2 2/53 Measuring and Modeling Differential Movement at Railroad Track Transitions Timothy D. Stark Stephen T. Wilk Jerry G. Rose Yang Jiang Congyue Fang Stark et al. (2015)

3 Outline 3/53 1. Identify problematic factors 2. Develop non-invasive measuring system 3. Evaluate design & repair measures 4. Dynamic numerical modeling 5. Substructure modulus 6. Summary

4 Open deck Wing walls Turn Fill height Identify Problematic Factors Soil type Fouling Poor drainage Grade crossing Rail joints Gaps 4/53

5 Tie-Ballast Gap Six instrumented Amtrak sites Wheel loads and vertical displacements with depth Upland Street Upland (60 ft.) Open track Upland (15 ft.) Transition zone Upland (60 ft.) 5/53 Upland (15 ft.)

6 Transient Vertical Displacements Upland (60 ft.) Upland (15 ft.) 6/53 Stark et al. (2015) Same Acela Power Car Upland (60 ft.) good support Upland (15 ft.) poor support Greater LVDT #1 transient vertical displacement (note different y-axis) LDVTs #2 to 5 delayed Erratic vertical displacements Rail rebound Identified tie-ballast gap

7 Good Tie Support 7/53 Loaded freight train, 25 mph

8 Poor Tie Support 8/53

9 Tie-Ballast Gap Tie-Ballast Gap Model Load-Displacement Behavior 9/53 Tie-ballast gap 0.25 mm v. 1.4 mm Gap can increase with time Upland (15 ft.): 1.4 mm (January 2013) Upland (15 ft.): 6.7 mm (July 2014)

10 Ballast Load-Displacement Curve Tie-Ballast Gap Load-Displacement Behavior 10/53 Tie-ballast gap <0.5 mm v. ~2.5 mm Norfolk Southern: Loaded and unloaded cars Model load-displacement curve

11 Load Redistribution 11/53 Limited knowledge from one tie-ballast gap (Tie 5): Gaps at surrounding ties affect load distribution (numerical modeling) Need gap heights of adjacent ties (accelerometers)???

12 Outline 12/53 1. Identify problematic factors 2. Develop non-invasive measuring system 3. Evaluate design & repair measures 4. Dynamic numerical modeling 5. Substructure modulus 6. Summary

13 Non-Invasive Instrumentation 13/53 Non-invasive instrumentation Accelerometers Tie accelerations & loads (heartbeat) High-speed video cameras Rail and tie displacements 10 field sites Good and poor support

14 Accelerometers 14/53 Indicators of poor tie support Greater tie acceleration 30g v. 5g < 5g is good support F = m*a Time Domain Frequency Domain

15 High Speed Video Cameras 15/53 6 ft. 14 ft. 8 accelerometers & 2 video cameras Reoccurring track geometry problems Rail-tie (#2) & Tie-ballast gap (#3) Rail and tie displacements Tie accelerations Double integration Centerbound tie Effect of air tamping

16 Video of Ties #2 and #3 16/53

17 C#2 (14 ft.): Rail-Tie Gap 17/53 Large rail displacement (~0.4 inches; 7 mm) Matches unloaded gap height Small tie displacement 14 ft.

18 C#2 (14 ft.): Rail-Tie Gap 18/53 ~0.4 mm gap Large rail displacement Some rail rebound Small tie displacement (~0.4 inches; 10 mm) (~ inches; 3 5 mm) 14 ft.

19 C#3 (20 ft.): Rail & Ballast Gap 19/53 Full time history Both rail and tie displacement Rail: ~0.2 in (~5 mm) Tie: ~0.25 in (~6 mm) Less rail movement than C#2 20 ft.

20 C#3 (20 ft.): Rail & Ballast Gaps 20/53 Both rail and tie displacing Greater tie displacements b/c tie bending Centerbound tie? 20 ft.

21 Summarize C#2 (14 ft.) v. C#3 (20 ft.) C#2 (14 ft.): Rail-Tie Gap C#3 (20 ft.): Rail & Ballast Gap 21/53 Greater rail displacement near bridge (C#2) Greater substructure settlement - cantilevered

22 Accel #2 (14 ft.) Accelerometers Accel #3 (20 ft.) 22/53 ~10g ~20g Tank Cars All responses >5g!

23 Accelerometers v. Video Cameras 23/53 C#2 (14 ft.): Rail-Tie Gap C#3 (20 ft.): Rail & Ballast Gap Video Camera Video Camera ~0.25 to 0.30 inch peak Tie displacement ~0.06 inch peak Tie displacement ~0.05 inch Tie displacement ~0.20 to 0.25 inch Tie displacement Accelerometer Accelerometer Target and accelerometer on tie Camera v. double integration Similar vertical displacements Stark et al. (2015)

24 Accel #3 (20 ft., East) Centerbound Tie???? Accel #4 (20 ft., West) 24/53 Wheel flats ~20 g Tank Cars ~20 g Tank Cars Compare Accel #3 & #4 Similar tie accelerations (~20g) More wheel flats at #4 20 ft.

25 First Train After Tamping C#2 (14 ft.) 25/ inches 0.4 inches 0.6 inches 1 st axle after tamping at Tie #2 (14 ft.) 0.25 rail and permanent tie V 14 ft.

26 Pre- & Post-Tamping C#2 (14 ft.) Pre-Tamping Post-Tamping (Train T6) 26/53 Pre-tamping v. 6 th train after tamping Smaller rail-tie gap (0.4 v. 0.3 ) Rail cantilevering again Similar tie-ballast behavior 14 ft.

27 Two Transitions 27/53 66 ft.

28 Effect of Train Direction Accel #8 (51 ft.) Accel #7 (36 ft.) 28/53 Accel #8 (51 ft.) Accel #7 (36 ft.) Train T5 (Loaded, 40 mph) Train T7 (Mixed, 52 mph) T5 southbound v. T7 northbound Train direction large effect on Accel #7 & #8 Bouncing from crossing and bridge Not observed at Accel #1 to #6 15 ft. Stark et al. (2015) 15 ft. 36 ft.

29 Future Non-Invasive Work Permanent installation Environmental and seasonal changes 29/53

30 Outline 30/53 1. Dip/gap development 2. Develop non-invasive measuring system 3. Evaluate design & repair measures 4. Dynamic numerical modeling 5. Substructure modulus 6. Summary

31 Complex Problem 31/53 Hastings, MN

32 Transition Zone Scorecard 32/53 Minimize differential transient and permanent displacements Questions: Which components need to be addressed? How to address them in most costeffective manner? Measure performance: Accelerometers High-speed video cameras Transition and Bridge Displacement Component Rail compression Rail-tie gap Tie pad/plate displacement Tie displacement Tie-ballast gap Ballast displacement Subballast displacement Subgrade displacement Lateral displacement Noticeable Transient T B Noticeable Permanent T B Total

33 Open Bridge Deck 33/53 Timber tie open bridge deck Tie-ballast gaps Ballast, subballast, and subgrade displacement Lateral displacement Transition and Bridge Displacement Component Noticeable Transient T B Rail compression X X Rail-tie gap Tie pad/plate displacement X X Tie displacement X X Tie-ballast gap Ballast displacement X X Subballast displacement X X Subgrade displacement X X Lateral displacement X X X X Noticeable Permanent T B Total????

34 Well-Performing Design 34/53 Design attributes Ballasted bridge deck HMA underlayment Consolidated fill Concrete wing walls Transition and Bridge Displacement Component Noticeable Transient T B Rail compression X X Rail-tie gap Tie pad/plate displacement X X Tie displacement X X Tie-ballast gap Noticeable Permanent T B Ballast displacement X X X X Subballast displacement Subgrade displacement Lateral displacement Total????

35 Outline 35/53 1. Dip/gap development 2. Identify problematic factors 3. Develop non-invasive measuring systems 4. Evaluate design & repair measures 5. Dynamic numerical modeling 6. Substructure modulus 7. Summary

36 Cart and Open Track 36/53

37 Gap Model 37/53

38 Load Redistribution 38/53 10% 20% 40% 20% 10% ~40% 0.46 seconds ~20% ~10%

39 Open Track Load Redistribution 39/53

40 Magnitude of Tie-Ballast Gap =? 40/53 Tie-ballast gaps > 1 mm Increase applied loads Field Measurements Laboratory Box Tests (Selig and Waters, 1994) Tie-ballast gap Permanent vertical displacements Load redistribution numerical modeling Impact loads - accelerometers

41 Bridge Approach Model 41/53

42 Bridge Approach No Gaps & Constant TOR Stark et al. (2015) 42/53

43 Bridge Approach No Gaps & Constant TOR Time History Distance from Abutment 43/53 Wheel-rail contact force Time history v. distance from abutment (decouple front and back wheels) Load amplification 30% increase about 10 feet (5 ties) from abutment Tie-ballast gap load amplification 200% increase of tie-ballast load

44 Complete Bridge Model 44/53

45 Outline 45/53 1. Dip/gap development 2. Develop non-invasive measuring system 3. Evaluate design & repair measures 4. Dynamic numerical modeling 5. Substructure modulus 6. Summary

46 BSPA 46/53 Ballast Seismic Property Analyzer (BSPA) Measure modulus using seismic waves Impact hammer and accelerometers Raleigh wave velocity (V r ) Non-invasive, portable BSPA orientations Across tie (center) Across tie (ends) Parallel to tie

47 Substructure Modulus Track geometry problems Substructure settlement due to low modulus Optimal ballast density Loose ballast state after placement and tamping Relate to modulus Achieve desired modulus Subballast/subgrade modulus Effect of fouling 47/53

48 Ballast Modulus Fouling 48/53 Material Type Dry & Wet Clean Ballast Dry Fouled Ballast Seismic Testing Young s Modulus (ksi) Upland (60 ft.) January 2015 (Rain) ~29 ksi June 2015 ~55 ksi 47% reduction Wet Fouled Ballast 20-25

49 Additional Applications 49/53 Tie integrity Relate to tie modulus Both concrete and timber ties

50 Summary 50/53 Differential transient and permanent displacements lead to dip Account for all displacements in bridge repair & design Poor track support Higher tie accelerations (>5g) Impact loads Higher rail and/or tie displacements Load redistribution Impact loads at bridge approach Permanent site BSPA Measure field ballast modulus Effect of fouling Tie integrity

51 Dip Development / Track System Gaps 51/53 1. New or freshly tamped track 2. Loading causes transient vertical displacements and ballast rearrangement. 3. Rail pulls tie up creating tie-ballast gap and other gap(s).

52 Dip Development / Track System Gaps 52/53 4. Rail can cantilever 5. Increased ballast loads from tieballast gap F = m*a & accelerometers 6. TOR developing permanent vertical displacements/ Dip in transition zone

53 Acknowledgments Federal Rail Administration Hugh Thompson, Ted Sussumann, & Cam Stuart Amtrak Dave Staplin, Steve Chrismer (LTK), and Mike Tomas CSX - Ed Sparks and Chris Garrett P&L - Tom Garrett and Gerald Gupton TTI Russ Rogers UP Caleb Douglas University of Kentucky Drs. Jerry Rose & Reginald Souleyrette Macy Purcell & John Magner Jordan Haney & Alex Wang University of Illinois at Urbana-Champaign Yang Jiang & Arthur Tseng Congyue Fang FRA Seismic Testing & Transitions Projects Carl Ho, Soheil Nazarian, Mark Baker, Erol Tutumluer, Jim Hyslip, and Deb Mishra 53/53

54 54/53 Measuring and Modeling Differential Movement at Railroad Track Transitions Timothy D. Stark Stephen T. Wilk Jerry G. Rose Yang Jiang Congyue Fang Stark et al. (2015)