Railroad turnout frog profile geometry and elasticity optimization using revenue service wheel profiles

Railroad turnouts are essential track infrastructure elements facilitating train movements between adjacent and diverging tracks. Most turnouts consist of three sections: the switch area, closure area, and frog area. The turnout frog induces significant wheel impacts as the wheel traverses through the turnout. These impacts are primarily attributed to both the frog profile geometry, which includes a gap (i.e., flangeway) between the wing rail and the point, as well as the variation in vertical track stiffness along the turnout. Given the high resiliency and reliability expectations for heavy axle load (HAL) freight infrastructure in North America (N.A.), improvement of turnout frog wear and impact resistance is crucial. My dissertation aims to optimize both the profile geometry of the frog and the elasticity of the turnout, thereby reducing wear and damage, leading to longer life cycles and fewer maintenance interventions. Given that previous studies on turnout optimization predominantly relied on design wheel profiles or a limited subset of wheels for wheel-rail interaction analysis, I developed and leveraged five representative revenue service wheel profiles. These profiles were selected based on the severity of hollow tread using a dataset of one million revenue service wheel profiles. In the geometry optimization phase, static geometric interaction analyses were conducted on 30 unique frog geometries. Wheel impacts during the wheel transition were quantified for each case using 400 randomly extracted revenue service wheel profiles. Among the geometries analyzed, the frog design featuring a gradual point slope and lower wing rail height demonstrated an average 28% reduction in wheel impacts compared to the existing frog design. To account for dynamic aspects, finite element analysis (FEA) was conducted on three validated frog geometries: the existing design, the geometry proposed through static analysis, and a version incorporating a longitudinal wing slope. The contact forces between the wheel and frog across five wheel profiles were quantified under three different train speeds, and the results showed that the geometry with the longitudinal wing slope provided an average wheel impact reduction of 46% compared to the existing frog design. Finally, under tie pads (UTPs) were introduced to further reduce wheel impacts at the frog point and minimize vertical track stiffness variations throughout the turnout. Laboratory experiments were conducted to evaluate the performance of UTPs with varying material properties, and the results were used to assess the impact of UTP characteristics and guide the selection of appropriate UTP properties to optimize turnout elasticity. A 3D turnout model was developed using the commercial multibody simulation (MBS) software VI-Rail, investigating four UTP properties and three rail pad stiffness levels. Although the difference in wheel impact magnitudes between no-UTP case and soft UTPs was limited to only 0.41%, the forces transferred from the crosstie to the ballast were reduced by 29% with soft UTPs compared to the no-UTP case. Additionally, adopting soft rail pads reduced wheel impacts for wheels in good condition but increased them for hollow worn wheels. Furthermore, UTPs improved track stiffness consistency by combining soft rail pads throughout the turnout with stiff UTPs in the frog section. This configuration achieved consistent track stiffness along the turnout, limiting displacement and corresponding stiffness variations to 2.3% and 6.9% for the switch and frog sections, respectively.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Lee, Jaeik

Contributors dc:contributor

• Edwards, John Riley
• Barkan, Christopher Paul Lyman
• Tutumluer, Erol
• Yang, Zhen

• Railroad Turnout
• Revenue Service Wheel Profiles
• Geometry Optimization
• Elasticity Optimization
• Finite Element Analysis (FEA)
• Multibody Simulation (MBS)

Statement dc:rights

• Copyright 2025 Jaeik Lee

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129373

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129373