KENTRACK Version Railway Trackbed Structural Design Software

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Hector Cannon
5 years ago
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1 KENTRACK Version Railway Trackbed Structural Design Software

2 Background KENTRACK Developed specifically to analyze HMA trackbeds Has the versatility to analyze all-granular trackbeds Initially a DOS based program Upgraded to a windows based platform with a Graphic User Interface

3 Superposition of Loads S ' 1 S 2 P 1 P S 4 P 2 P S4 P S3 S2 S1 S2 S3 S4 P1 P2 P3 P S2 S1 S2 S3 S4 S4 S3 S2 S1 S2 S3 S4 S4 S3 S2 S1 S2 S3 S4 S4 S3 S2 S1 S2

4 x Finite Element Method RAIL: y(my) i y l j x w(p) z TIE: x(mx) i l j y w(p) z i SPRING: w(p) j - To calculate stresses and strains in rail and tie

5 Multilayered System a a q r E1 z1 z2 E2 zn-2 H En-1 n-1 En n z - To calculate stresses and strains in the layers

6 Material Properties - HMA trackbed is comprised of ballast, HMA and subgrade - All-granular trackbed is comprised of ballast, subballast and subgrade - Different equations are used to describe the material properties

7 Ballast - In a new trackbed it behaves non-linearly - In an aged trackbed it behaves linearly E K 1 K 2 z( ) K Subgrade - Linearly elastic material

8 Hot Mix Asphalt (HMA) Visco-elastic material The dynamic modulus of HMA depends on - Temperature - Aggregate passing No. 200 sieve in % - Volume of bitumen % - Volume of air voids % - Asphalt viscosity - Load frequency

9 Damage Analysis - Based on minor linear damage analysis criteria - Performed by periods (seasons, months) L i n 1 N 1 N a p orn d

Predicted number of repetitions Wheel Load = 36000 lb/wheel For one car the total weight = 36000 lb/wheel x 8 = 286,000 lb/rep / 2000 = 143 ton/rep The

10 Predicted number of repetitions Wheel Load = lb/wheel For one car the total weight = lb/wheel x 8 = 286,000 lb/rep / 2000 = 143 ton/rep The number of repetitions assumed per year The traffic per year = 200,000 rep/yr = 200,000 rep/yr x 143 ton/rep = 28,600,000 GT/yr / 1 x 10 6 = 28.6 MGT/yr

11 HMA Damage Analysis - Fatigue cracking controls failure - Fatigue cracking is governed by the tensile strain at the bottom of HMA - Based on highway experience - Number of allowable repetitions (N a ) before failure N a E t a 0.853

12 Subgrade Damage Analysis - Excessive permanent deformation controls failure - Deformation is governed by the vertical compressive stresss on top of subgrade - Based on highway experience - Number of allowable repetitions (N d ) before failure N d E c s 3.583

13 Stresses and Strains Asphalt Trackbed All-Granular Trackbed

14 Methodology Critical outputs for the two sections Critical Outputs Variable Standard HMA trackbed Standard Ballast Trackbed Subgrade Vertical Compressive Stress (psi) HMA Tensile Strain (in/in) N/A Service life of Subgrade (yrs) Service life of HMA (yrs) 19.8 N/A

15 Vertical Compressive Stress (psi) Effect of Subgrade Modulus on σ c Axle Load 36 tons HMA Trackbed Ballast Trackbed Subgrade Modulus (psi)

16 Predicted Service Life (yrs) Effect of Subgrade Modulus on L Axle load - 36 tons Subgrade Life in Ballast Trackbed Subgrade Life in HMA Trackbed HMA Life in HMA Trackbed Subgrade Modulus (psi)

17 HMA tensile Strain (in/in) Effect of Subgrade Modulus on ε t Axle load 36 tons Subgrde Modulus (psi)

18 Predictive Values Versus In-track Data Comparison of the KENTRACK Predictive values (KPV) Versus In-Track Data (ITD) for the CSX Mainline at Conway, Kentucky Thickness Ballast- HMA inches Vertical Compressive Stress on Ballast KPV/TTD psi Vertical Compressive Stress on HMA KPV/TTD psi Vertical Compressive Stress on Subgrade KPV/TTD psi 10 / / / / - 10 / / / / - Comparison of the KENTRACK Predictive values (KPV) Versus In-Track Data (ITD) at TTCI in Pueblo, Colorado Thickness Ballast- HMA inches Vertical Compressive Stress on Ballast KPV/TTD psi Vertical Compressive Stress on HMA KPV/TTD psi Vertical Compressive Stress on Subgrade KPV/TTD psi 12 / / / / / / / / 7.7

19 Summary KENTRACK is a versatile program that can be used to analyze HMA and all-granular trackbeds HMA trackbeds improve the service life and perform better than all-granular trackbeds Damage analysis values are conservative Subgrade modulus is a very important factor in trackbed design

Kentrack, A Performance-Based Layered Elastic Railway Trackbed Structural Design and Analysis Procedure A Tutorial

Kentrack, A Performance-Based Layered Elastic Railway Trackbed Structural Design and Analysis Procedure A Tutorial Jerry G. Rose University of Kentucky Lexington, KY USA Justin D. Brown University of Kentucky