Vision for Mechanistic Concrete Crosstie and Fastener System Design

J. Riley Edwards, Brandon J. Van Dyk, and Marcus S. Dersch

International Concrete Crosstie and Fastening System Symposium

8 June 2012 Urbana, IL

Vision for Mechanistic Design Slide 2

Outline• Mechanistic Design

– Definition

– Other Applications

– Process

– Objectives

• Path Forward

– Data Collection and Analysis

– Implementation

• Questions and Comments

Vision for Mechanistic Design Slide 3

Current Design Process• Mostly iterative, with focus on reduction of LCC

reduction of the crosstie and fastening system

• Loading “conditions” empirically derived

• Some loading conditions extrapolated (AREMA C-30, Table 30-4-4)

• Process can be driven by production and installation considerations

• Option for Improvement Mechanistic Design

Vision for Mechanistic Design Slide 4

Highway Example of Mechanistic Design

• MEPDG – Mechanistic-Empirical Pavement Design Guide

• Inputs – geometry, traffic, climate, materials

• Output – pavement responses to load, compute distresses and loss of ridability

• Apply to the rail industry?

Vision for Mechanistic Design Slide 5

What Is Mechanistic Design?

• Analytical approach not an iterative design process

• Uses loading data to develop a design that functions under expected loading conditions

• Requires design for specific failures modes or performance indicators

– e.g. RSD, center cracking, post insulator wear, etc.• Inputs – Crosstie and fastening system component

geometry, traffic (axle load and tonnage), climate, materials

• Outputs – Tie and fastening system responses (stresses/strains) to loads, performance characteristics, wear rates?

Vision for Mechanistic Design Slide 6

Mechanistic Design Process1. Quantify System Input Loads (Wheel Impact Load Data (WILD),

Instrumented Wheel Sets (IWS))

2. Qualitatively Establish Load Path (Free Body Diagrams, Basic Modeling, etc.)

– Establish the locations for load transfer, in need of further analysis and study

3. Quantify Loading Conditions at each Interface / Component (Including displacements)

– Laboratory and Field Experimentation

– Analytical Modeling (Basic FEM)

4. Link Quantitative Data to Component Geometry and Materials Properties

– Go / No-Go Materials Decision

Vision for Mechanistic Design Slide 7

Mechanistic Design Process (Cont.)

5. Relate Loading to Failure Modes (e.g. How does lateral loading relate to post insulator wear?)

6. Understand Interdependencies taking advantage of modeling techniques

– Run parametric analyses

– Sensitivity of property vs. performance

7. Development and Testing of Innovative Designs

• Novel rail pad, crosstie, insulator designs

• Geometry and materials improvements

8. Establish Mechanistic Design Practices

9. Adoption into AREMA Recommended Practices

Vision for Mechanistic Design Slide 8

Setting Design Thresholds

Fre

quen

cy

Load (e.g. Rail Seat Load)

Threshold #2Threshold #1

XFcs Gcs

Fts

Fcs’ Gcs’

GscFsc

Fsc’ Gsc’

Fst

Gst

Z

Fbi

Gbi’

Fbi’

Fbo’Gbi

Fbo

Bbp

Bbp’

Fic

Gic’Fic’

Fos

Gic

Fos’

Fps’

Bpr

Bpr’

Fps

Legend

Reaction

Friction

Input Load

F = Field

G = Gauge

B = Base

Subscripts

b – rail base

p – pad

i – insulator clip bearing area

c – clip

s – shoulder

o – insulator post

t - tie

Vision for Mechanistic Design Slide 10

20 kips

95%

Source: Amtrak, Edgewood, MD, October 2011

Distribution of Vertical Wheel Loads

Vision for Mechanistic Design Slide 11

Areas of InvestigationFasteners/ Insulator

• Strain of fasteners

• Stresses on insulator

• Internal strains

– Midspan

– Rail Seat

• Stresses at rail seat

• Global displacement of the crosstie

Rail• Stresses at rail seat

• Strains in the web

• Displacements of head/base

Concrete Crossties

Vision for Mechanistic Design Slide 12

Planned Locations for Field Testing• Monticello Railway Museum• Transportation Technology

Center (TTC)– July 2012– November 2012– Spring 2013

• Class I Railroads– Amtrak– BNSF– Union Pacific Transportation Technology Center (TTC)

Vision for Mechanistic Design Slide 13

Future Work• Evaluation and analysis of WILD data to better evaluate

input loads

– Major discussion point from AREMA Committee 30, Subcommittee 4 (Concrete Tie Technology) Meeting

• Conduct laboratory and field testing to gain further insight on loads transferred through each component

• Development of greater understanding of dynamic interactions between system components

• Utilize output from instrumentation and modeling efforts to establish loading environment

Vision for Mechanistic Design Slide 14

Path Forward• Development of System Level Tie and Fastener Model

• Field and Laboratory Testing of Components and Systems

• Materials Research and Improvements (all components)

• Understand how deterioration methods are related to differing axle loadings (important on shared corridors)

• Development of mechanistic design procedures Adoption into AREMA Recommended Practices

• Ultimate objective increase safety and lower life cycle costs of the crosstie and fastening system

Vision for Mechanistic Design Slide 15

Acknowledgements

• Funding for this research has been provided by theFederal Railroad Administration (FRA)

• Industry Partnership and support has been provided by– Union Pacific (UP) 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

FRA Tie and Fastener BAAIndustry Partners:

Vision for Mechanistic Design Slide 16

Contact Information

Brandon Van DykGraduate Research Assistante-mail: vandyk2@illinois.edu

Riley EdwardsLecturer

e-mail: jedward2@illinois.edu

Marcus DerschResearch Engineer

e-mail: vandyk2@illinois.edu