T R A N S I T C O O P E R A T I V E R E S E A R C H P R O G R A M TCRP REPORT 71 Track-Related Research Volume 6: Direct-Fixation Track Design Specifications, Research, and Related Material Part A Direct-Fixation Track Design and Example Specifications T R A N S P O R T A T I O N R E S E A R C H B O A R D May 2005 CONTENTS PART A SECTION 1 Direct Fixation Track Design SECTION 2 Direct Fixation Fastener Example Procurement Specification and Commentary SECTION 3 Direct Fixation Fastener Example Qualification and Production Test Specification and Commentary SECTION 4 Direct Fixation Trackwork Example Construction Specification and Commentary SECTION 5 Example Concrete Specification SECTION 1 Direct Fixation Track Design For TCRP Project D-07/Task 11 Development of Direct-Fixation Fastener Specifications and Related Material by Laurence E. Daniels Railroad Consulting Engineer William Moorhead TRAMMCO May 2005 SECTION 1 Direct Fixation Track Design Table of Contents I. Introduction .........................................................................................................1 A. Purpose ...........................................................................................................1 B. Background .....................................................................................................1 C. Scope ..............................................................................................................2 II. Discussion on Basics ..........................................................................................8 A. General Configurations....................................................................................8 B. Mechanics Affected by Direct Fixation Fasteners............................................8 1. Vibration Mechanics.....................................................................................9 2. Electrical Isolation and Stray Current.........................................................10 C. Perspectives on Fastener Stiffness and Materials.........................................11 D. Variability of Fastener Properties...................................................................13 III. Direct Fixation Track Design Steps ...............................................................14 IV. Determining Loads ........................................................................................17 A. Vertical Wheel Loads.....................................................................................17 1. Vertical Fastener Loads .............................................................................18 B. Lateral Wheel Loads......................................................................................18 1. Lateral Loads on Individual Fasteners .......................................................20 C. Longitudinal Rail Loads .................................................................................22 1. Vehicle Traction .........................................................................................22 2. Rail Break ..................................................................................................22 D. Track Response to Loads..............................................................................27 V. Direct Fixation Materials....................................................................................27 A. Rubbers and Synthetic Elastomers ...............................................................27 1. Rubber Chemistry and Manufacturing .......................................................27 2. Synthetic Rubber Chemistry and Manufacturing........................................32 3. Stiffness and Fastener Geometry ..............................................................33 4. Elastomer Fatigue......................................................................................36 B. Reinforced Concrete Material........................................................................47 1. General – Concrete Configurations............................................................47 2. Concrete Issues .........................................................................................48 3. Grout Pads.................................................................................................56 4. Construction Method, Formwork and Concrete Delivery............................56 5. Placement, Finishing and Curing of the Track Concrete............................60 6. Construction Tolerances: Dimensions, Voids, Flatness, Rebar Cover, etc. ...................................................................................................................62 7. Inspection Criteria and Methods, NDT Testing ..........................................63 8. Repair Methods and Rework of Out-Of-Spec Concrete .............................65 9. Summary of Most Important Concrete Issues............................................66 10. Managing Concrete – Scopes....................................................................67 C. Metallic Components .....................................................................................69 VI. Fastener Design ............................................................................................79 A. General Considerations.................................................................................79 B. Fastener Mechanical and Electrical Properties..............................................80 1. Fastener Static Stiffness. ...........................................................................80 2. Fastener Dynamic Characteristics, , ...........................................................85 3. Fastener Electrical Properties....................................................................99 C. Lateral Fastener Stiffness and Gage Retention...........................................103 D. Fastener Stiffness Variation.........................................................................104 E. Anchor Bolts ................................................................................................107 1. Anchor Bolt Size. .....................................................................................107 2. Clamping Force........................................................................................107 3. Insert Pullout Force..................................................................................108 4. Total Required Bolt Tensile Load.............................................................108 5. Bolt Torque. .............................................................................................109 6. Design to Prevent Bolt Loosening............................................................110 7. Insert Pullout Resistance. ........................................................................111 VII. Fastener Spacing ........................................................................................112 VIII. Track Transitions .........................................................................................112 A. Approach Slabs ...........................................................................................113 B. Asphalt Underlayment .................................................................................113 C. Track Beams ...............................................................................................113 D. Vary Direct Fixation Fastener Spacing and Tie Spacing .............................115 IX. Direct Fixation Construction Tolerances and Specifications........................115 A. Construction Specification Comments.........................................................115 B. Direct Fixation Tolerances...........................................................................116 Attachment 1A. Relationships Between Fastener Stiffness, Track Stiffness and Track Modulus.........................................................................................118 Attachment 1B. Direct Fixation Track Examples.....................................................120 Attachment 1C. Lateral Thermal Rail Load on a Fastener......................................127 Attachment 1D. Broken Rail Gap Derivation...........................................................130 Attachment 1E. Derivation of Dynamic Fastener Characteristics ...........................132 SECTION 1 Direct Fixation Track Design List of Figures Figure 1. Examples of Bonded and Non-Bonded Plate-Type Direct Fixation Fasteners. Rigid Rail Clip illustrated. ...................................................3 Figure 2. Example of Different Direct Fixation Fastener Designs.........................4 Figure 3. Examples of Bonded Plate-Type Direct Fixation Fasteners..................5 Figure 4. Examples of Bonded Plate-Type Direct Fixation Fasteners..................6 Figure 5. Examples of Non-Bonded Direct Fixation Fasteners. ...........................6 Figure 6. Non-Bonded Fastener (left); Embedded Block Track (right) .................7 Figure 7. Manufacturing Fastener Stiffness Variability for 20 Fasteners of the Same Design within the Same Manufacturing Run.............................14 Figure 8. Illustration of Lateral Force Estimate. .................................................19 Figure 9. Wheel Lateral Offset in Curves. Assumptions: Wheel Dia. = 28”, Track Gauge = 56 ½”..........................................................................21 Figure 10. Lateral Fastener Force from Thermal Rail Force for 115 RE Rail for Different Temperatures above the Neutral