Turnouts - 1© Transportation Technology Center, Inc., a subsidiary of the Association of American Railroads, 2015

Section 4 - Turnout Modeling

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© TTCI/AAR, 2015, Turnouts p2®

Turnout Nomenclature

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Switch Geometry

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Rail Profile Variations & W/R Contact

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Turnout Modeling Methodology in NUCARS® Traditional W/R rigid contact model (WNT tables)

Unstable (chattering)when two-point contact occurs Can’t simulate rail roll movement

Penetration W/R contact model (Fit files) Instable (spikes)when rail profile shape changes

Double rail model (Fit files) Stable results Involve primary and secondary rail trajectories and

profile variations Has been used for various special track work

(foundation, frog, crossing etc.) modeling

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Turnout Modeling - Rigid W/R Contact Model

Traditional rigid W/R Contact Model In .run file, use key word: \W/R Contact Master

Geometry File 'AREMA20.WRM’ includes a series of WNT files See Chapter 11.5 for details of making a WRM file

Can’t use Track Model Can only use spring and damper connections

underneath rail Need to calculate guard rail geometry Guard rail rigidly attached to stock rail See Chapter 11.6 for details of making WNT file for

flange back contact with guard rail

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Turnout Modeling - Penetration Contact Model

W/R Penetration Model In .RUN file, use key word: \Rail Geometry Master

File 'AREMA20.RLM’ includes a series of FIT files See Chapter 11.5 of for details of making RLM file

Can use Track Model or use spring and damper connections underneath rail

Guard rail is defined in Fit file (flangeway clearance, guard rail height, stiffness, damping etc.)

Guard rail can move relative to stock rail

© TTCI/AAR, 2015, Turnouts p8®

Typical Measured Switch Rail Profiles

Measured every foot