1. Vision for Mechanistic Concrete Crosstie and Fastener System Design
International Concrete Crosstie and Fastening System Symposium
8 June 2012  Urbana, IL
J. Riley Edwards, Brandon J. Van Dyk, and Marcus S. Dersch

2. Outline Mechanistic Design Definition Other Applications Process
Objectives
Path Forward
Data Collection and Analysis
Implementation
Questions and Comments

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 )
Process can be driven by production and installation considerations
Option for Improvement  Mechanistic Design

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?

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?

6. Mechanistic Design Process
Quantify System Input Loads (Wheel Impact Load Data (WILD), Instrumented Wheel Sets (IWS))
Qualitatively Establish Load Path (Free Body Diagrams, Basic Modeling, etc.)
Establish the locations for load transfer, in need of further analysis and study
Quantify Loading Conditions at each Interface / Component (Including displacements)
Laboratory and Field Experimentation
Analytical Modeling (Basic  FEM)
Link Quantitative Data to Component Geometry and Materials Properties
Go / No-Go Materials Decision

7. Mechanistic Design Process (Cont.)
Relate Loading to Failure Modes (e.g. How does lateral loading relate to post insulator wear?)
Understand Interdependencies taking advantage of modeling techniques
Run parametric analyses
Sensitivity of property vs. performance
Development and Testing of Innovative Designs
Novel rail pad, crosstie, insulator designs
Geometry and materials improvements
Establish Mechanistic Design Practices
Adoption into AREMA Recommended Practices

8. Setting Design Thresholds
Frequency
Load (e.g. Rail Seat Load)

9. Z X Fcs Gcs Fts Fcs’ Gcs’ Fic Gic’ Fic’ Fos Gic Fos’ Fps’ Bpr Bpr’ Fps
Gsc
Fsc
Fsc’
Gsc’
Subscripts
b – rail base
p – pad
i – insulator clip bearing area
c – clip
s – shoulder
o – insulator post
t - tie
Fbi
Gbi’
Fbi’
Fbo’
Gbi
Fbo
Bbp
Bbp’
Legend
Reaction
Friction
Input Load
F = Field
G = Gauge
B = Base
Fst
Gst

10. Distribution of Vertical Wheel Loads
95%
20 kips
Source: Amtrak, Edgewood, MD, October 2011

11. Areas of Investigation
Rail
Stresses at rail seat
Strains in the web
Displacements of head/base
Fasteners/ Insulator
Strain of fasteners
Stresses on insulator
Internal strains
Stresses at rail seat
Midspan
Global displacement of the crosstie
Rail Seat
Concrete Crossties

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, Inc.
High Tonnage Loop, Railroad Test Track
Exciting summer of data acquisition
Transportation Technology Center (TTC)

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

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

15. FRA Tie and Fastener BAA Industry Partners:
Acknowledgements
FRA Tie and Fastener BAA Industry Partners:
Funding for this research has been provided by the Federal 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

16. Contact Information
Brandon Van Dyk
Graduate Research Assistant
Marcus Dersch
Research Engineer
Riley Edwards
Lecturer