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Comparisons of Railroad Trackand Substructure ComputerModel Predictive Stress Valuesand In-Situ Stress MeasurementsBy: Dr. Jerry G. Rose, Ph.D., PEBei Su, MSCE andFrank Twehues, EIT

Earth Pressure CellComputerPredictsTekscan SensorMeasures

Tekscan SensorTekscan SensorTekscan SensorWooden TieBallastGeokon Pressure CellPressure CellSubballast/HMASubgradeGeokon PressureCellGeokon PressureCell

Pressure CellCellPlacementon Asphalt Geokon Model 3500-29 in. DiameterStrain GageSnap-MasterThermistor

Junction BoxPressure CellBatteryPressure Cell Measurement Configuration

Matrix-based array offorce sensitive cells Silver conductive electrodes Pressure sensitive ink –Conductivity varies Crossing of ink – strain gaugeView of Tekscan SensorsTekscan MeasurementConfiguration

Traditional Track StructureTrack Structure With Asphalt Underlayment– 5-10 feet beyond crossing– Typical highway dense-gradedbase mix– 0.5% higher asphalt content

Installation of HMA Underlayment Using PaverInstallation of HMA Underlayment by Back-Dumping

350 ft350 ft12 in.ballast4 in.4 in.HMAsubballast10 ft8 in.8 in.4 in.clay subgradePueblo, Colorado Longitudinal SectionExisting Conditions at Transportation Technology Center, Pueblo, Colorado

1000 ft9 in.1000 ft9 in.ballast5 in.HMA8 in.clay subgradeConway, Kentucky Longitudinal ViewExisting Conditions at Conway, Kentucky

Calibration Test Configuration Using theSatec Universal Testing Machine.

25Representative DynamicCompressive Stress onHMA Layer Measured forEmpty Coal Train on CSXTransportation Mainlineat Conway, KY8 in. ballast5 in. HMA20Initial 5 Cars1510507891011121314151617Time (s)20Four 6-Axle LocosHMA Compressive Stress (psi)HMA Compressive Stress (psi)Four 6-Axle Locos8 in. ballast8 in. HMA15Initial 5 Cars105045678910Time (s)1112131415

subgrade surfaceHMA surfaceCompressive Stress (psi)201510502.53.54.55.56.57.58.59.5Time (s)Dynamic Compressive Pressures Measured on TTCI Test Track

Compressive Stress Compressive Stress Compressive Stresson Ballaston HMAon SubgradeKPV/ITD, psiKPV/ITD, psiKPV/ITD, psi10 / 547.9 /21 / 1613.6 / -10 / 848.7 /22 / 1511.7 / -Comparison of the KENTRACK Predictive Values (KPV)Versus In-Track Data (ITD) for the CSX Mainline at Conway, VerticalCompressive Stress Compressive Stress Compressive Stresson Ballaston HMAon SubgradeKPV/ITD, psiKPV/ITD, psiKPV/ITD, kPa12 / 443.5 / -11.7 / 14.98.3 / 8.08/847 / -21.9 / 14.98.2 / 7.7Comparison of the KENTRACK Predictive Values (KPV)Versus In-Track Data (ITD) at TTCI in Pueblo, Colorado

286,000lb62,000lb180lb13 - 17psi2-4psi6psi100 - 200 psiVertical Pressure on Asphalt Surfaces for Various Loadings

In Track Placement During First TestTypical Pressure DistributionPlot from Tekscan SystemScale in PSI

Scale in PSIThis represents a typical pressure distributionbetween a steel tie plate and the rail.

RailRubber BladderMylarTeflon TekscanSensorTeflonMylarTie Plate

Scale in PSIThis represents a typical pressure distribution between a machinedsteel tie plate and the rail with an included rubber bladder.

Scale in PSIThis represents a typical pressure distribution betweena polyurethane plastic tie plate and the rail.

Ties4BT i e foreesSeB3nT i e fore soresSeB2nT i e fore soresBe Se1nTi fore soreBe SeDirenct fore sorlyAb Seov nso1TieresSensP2orTi astesSePn3Ti ast soresSePns4oTi astesSe rPn5Ti ast soresSPa ensostSe rnsor5Average Pressure (psi)500450400350300Positioning of Lead Wheelwith Respect to Sensor250200150100500Lead Wheel PositionSnapshot of the Lead WheelDirectly above the SensorLead Wheel OverSensorF 20985 lbf, P 437 psi

TiesB8Ti eforeesBe Sen6Ti fore soreBe Se4nfTies ore sorSeB2nT i e fore soresBe SeDinrect fore sorlyAb Seov nso2TieresSenPso4Ti astresSePns6oTi astesSe rPns8oTi astesSe r10PnsoTi astesSe rPanst sorSensor10Average Pressure (psi)700600500400Positioning of Lead Wheelwith Respect to Sensor3002001000Lead Wheel PositionSnapshot of the Lead WheelDirectly above the SensorLead Wheel OverSensorF 25372 lbf, P 529 psi

Rear Tires of Tractor of a 151,000 lb Loaded Coal Truck on ConcreteCrossing of Kentucky Coal Terminal, Mile Post 6.6. May 25, 20049842 lb135 psi72.93 in 2

Front Tire of a CSXT Suburban on Asphalt Parking Lot in Ashland OilCompany. May 25, 20041652 lb75 PSI22.15 in 2

Rear Tire of a CSXT Suburban on Asphalt Parking Lot in Ashland Oil Company.May 25, 20042197 lb81 PSI27.15 in 2

Tire TreadMylarTeflonTekscanSensorAsphalt SurfaceTeflon Mylar

FINDINGS KENTRACK -- utilized to predict stresses inthe track structure and foundation Earth Pressure Cells -- provide direct measurement ofpressures (stresses) in the track structure andfoundation Computer Predictions -- compare favorably withPressure Cell Measurements at theballast/subballast and subballast/subgradeinterfaces Pressure Cells -- technique presently being developedfor tie/ballast interface pressure measurements

FINDINGS KENTRACK -- utilized to predict stresses in the trackstructure and foundation Earth Pressure Cells -- provide directmeasurement of pressures (stresses) inthe track structure and foundation Computer Predictions -- compare favorably withPressure Cell Measurements at theballast/subballast and subballast/subgradeinterfaces Pressure Cells -- technique presently being developedfor tie/ballast interface pressure measurements

FINDINGS KENTRACK -- utilized to predict stresses in the trackstructure and foundation Earth Pressure Cells -- provide direct measurement ofpressures (stresses) in the track structure andfoundation Computer Predictions -- compare favorablywith Pressure Cell Measurements at theballast/subballast andsubballast/subgrade interfaces Pressure Cells -- technique presently being developedfor tie/ballast interface pressure measurements

FINDINGS KENTRACK -- utilized to predict stresses in the trackstructure and foundation Earth Pressure Cells -- provide direct measurement ofpressures (stresses) in the track structure andfoundation Computer Predictions -- compare favorably withPressure Cell Measurements at theballast/subballast and subballast/subgradeinterfaces Pressure Cells -- technique presently beingdeveloped for tie/ballast interfacepressure measurements

Findings (conti.) Tekscan Sensors -- technology developedfor using them for track pressuremeasurements at the rail/plate andplate/tie interfaces– Sensors are thin and non-intrusive– Repeatability is very good - consider loads applied,loading rate, and surrounding material– Calibration is very important consideration– Thin rubber bladder must be used on steel tie plates– Shim stock is necessary– Wide range of track related applications

Findings (conti.) Tekscan Sensors -- technology developed for usingthem for track pressure measurements at therail/plate and plate/tie interfaces– Sensors are thin and non-intrusive– Repeatability is very good - consider loadsapplied, loading rate, and surroundingmaterial– Calibration is very important consideration– Thin rubber bladder must be used on steel tieplates– Shim stock is necessary– Wide range of track related applications

Potential Tekscan Applications Superelevation – Curve design Impact pressures – diamonds-- bridge approaches Plates, Pads, Fastenings & Ties ? ? ? ? ?

Acknowledgements

Geokon Pressure Cell Ballast Subballast/HMA Wooden Tie Subgrade Geokon Pressure Cell Tekscan Sensor Tekscan Sensor Geokon Pressure Cell Pressure Cell Tekscan Sensor Geokon Model 3500-2 9 in. Diameter Strain Gage Snap-Master Thermistor Pressure Cell Cell Placement on Asphalt .