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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: [email protected]
Riley EdwardsLecturer
e-mail: [email protected]
Marcus DerschResearch Engineer
e-mail: [email protected]