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<p>Continuous welded rail (CWR) systems installed on concrete bridges are highly sensitive to restrained thermal expansion, particularly in hot-climate regions where rail temperatures routinely exceed the assumptions underlying conventional design standards. This study presents a validated three-dimensional finite-element and parametric optimisation framework for quantifying track-bridge interaction in bridge-mounted CWR systems subjected to extreme thermal and mechanical loading. The framework is applied to a representative bridge segment along the Kano-Maradi-Dutse Standard Gauge Railway Corridor in northern Nigeria, incorporating Eurocode-consistent thermal actions (uniform temperature change and vertical deck gradients), braking and traction forces, LM71 vertical train loading, nonlinear ballast-fastener restraint, bearing friction, and expansion joint behaviour. Simulations conducted over a realistic rail temperature range of 20–45&#xa0;°C demonstrate that thermal loading is the dominant driver of longitudinal system response, accounting for more than 70% of total rail stress variation. Axial rail stresses increase from approximately ± 3&#xa0;MPa at 20&#xa0;°C to peak values of about + 20&#xa0;MPa in compression and -15&#xa0;MPa in tension at 45&#xa0;°C. Braking forces generate the largest mechanically induced longitudinal displacements (up to ± 6&#xa0;mm), exceeding those from traction (≈ ± 4.5&#xa0;mm), while vertical train loads exert only a minor direct influence on longitudinal behaviour (≈ 1.7–2.5&#xa0;mm), acting primarily as a secondary modifier of effective restraint stiffness. When thermal and braking actions are combined, compressive rail stresses are amplified by nearly 25% relative to individual load cases, highlighting the nonlinear coupling between thermal pre-stress and frictional restraint. Parametric optimisation identifies fastener stiffness as the key controllable parameter governing the balance between thermal accommodation and structural safety. An optimal stiffness range of 30–40&#xa0;kN/mm is established, within which longitudinal displacements remain below 10&#xa0;mm and rail stress utilisation satisfies Eurocode serviceability limits (<i>σ/σᵧ</i> ≤ 0.6). This study contributes the first validated three-dimensional finite-element parametric optimisation framework explicitly tailored to extreme thermal regimes in hot-climate railway corridors, delivering quantifiable design guidance that extends Eurocode provisions to thermally aggressive environments while maintaining full compliance with serviceability and safety criteria. All configurations within this range also comply with deck crack width and bearing performance criteria under worst-case combined loading. The proposed framework provides a robust decision-support tool for calibrating fastener stiffness, bearing behaviour, and expansion allowances in bridge-mounted CWR systems. By explicitly capturing extreme thermal regimes and load interaction effects, the study delivers climate-adaptive design guidance and supports the safe extension of Eurocode-based provisions to railway infrastructure operating in hot and thermally aggressive environments.</p> Graphical abstract <p></p>

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Parametric optimization of track-bridge interaction in continuous welded rail systems under extreme thermal loading: a finite-element approach

  • 期刊论文

  • 发表日期：

    2026年5月20日

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  • Efiok Etim Nyah,
  • Danjuma Dauda Abubakar,
  • Okorie Austine Uche

摘要

Continuous welded rail (CWR) systems installed on concrete bridges are highly sensitive to restrained thermal expansion, particularly in hot-climate regions where rail temperatures routinely exceed the assumptions underlying conventional design standards. This study presents a validated three-dimensional finite-element and parametric optimisation framework for quantifying track-bridge interaction in bridge-mounted CWR systems subjected to extreme thermal and mechanical loading. The framework is applied to a representative bridge segment along the Kano-Maradi-Dutse Standard Gauge Railway Corridor in northern Nigeria, incorporating Eurocode-consistent thermal actions (uniform temperature change and vertical deck gradients), braking and traction forces, LM71 vertical train loading, nonlinear ballast-fastener restraint, bearing friction, and expansion joint behaviour. Simulations conducted over a realistic rail temperature range of 20–45 °C demonstrate that thermal loading is the dominant driver of longitudinal system response, accounting for more than 70% of total rail stress variation. Axial rail stresses increase from approximately ± 3 MPa at 20 °C to peak values of about + 20 MPa in compression and -15 MPa in tension at 45 °C. Braking forces generate the largest mechanically induced longitudinal displacements (up to ± 6 mm), exceeding those from traction (≈ ± 4.5 mm), while vertical train loads exert only a minor direct influence on longitudinal behaviour (≈ 1.7–2.5 mm), acting primarily as a secondary modifier of effective restraint stiffness. When thermal and braking actions are combined, compressive rail stresses are amplified by nearly 25% relative to individual load cases, highlighting the nonlinear coupling between thermal pre-stress and frictional restraint. Parametric optimisation identifies fastener stiffness as the key controllable parameter governing the balance between thermal accommodation and structural safety. An optimal stiffness range of 30–40 kN/mm is established, within which longitudinal displacements remain below 10 mm and rail stress utilisation satisfies Eurocode serviceability limits (σ/σᵧ ≤ 0.6). This study contributes the first validated three-dimensional finite-element parametric optimisation framework explicitly tailored to extreme thermal regimes in hot-climate railway corridors, delivering quantifiable design guidance that extends Eurocode provisions to thermally aggressive environments while maintaining full compliance with serviceability and safety criteria. All configurations within this range also comply with deck crack width and bearing performance criteria under worst-case combined loading. The proposed framework provides a robust decision-support tool for calibrating fastener stiffness, bearing behaviour, and expansion allowances in bridge-mounted CWR systems. By explicitly capturing extreme thermal regimes and load interaction effects, the study delivers climate-adaptive design guidance and supports the safe extension of Eurocode-based provisions to railway infrastructure operating in hot and thermally aggressive environments.

Graphical abstract