Continuously Welded Rail (CWR) Buckling Calculator
Calculate longitudinal thermal stresses, rail neutral temperature deviations, ballast lateral resistance, and track buckling ("sun kink") safety per AREMA Chapter 5.
Rail Section Profile & Temperatures
Track Ballast Support & Curvature
Thermal Stress & Buckling Factor
| Summer Temperature Delta (ΔT_comp): | -- °C |
| Compressive Thermal Stress (per rail): | -- MPa |
| AREMA Critical Track Buckling Load (Pcr): | -- kN |
| Buckling Safety Margin (Pcr / P): | -- |
| Max Safe Rail Temp Before Buckling: | -- °C |
| Winter Peak Tensile Force (per rail): | -- kN (-- MPa) |
| Radial Curvature Force on Ballast: | -- kN/m |
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
What is Continuously Welded Rail (CWR) and why does it buckle in hot weather?
Continuously Welded Rail (CWR) welds standard rail sticks into continuous strings several miles long, eliminating the traditional bolted joints that cause track pounding and maintenance. However, because CWR is restrained from expanding longitudinally by rail anchors and heavy ballast, high summer temperatures generate immense compressive axial forces (often exceeding 1,000 kN per rail). If lateral ballast resistance is inadequate, the track snaps sideways in a violent buckle known as a "sun kink".
What is Rail Neutral Temperature (RNT) and how is it managed?
Rail Neutral Temperature (RNT, or preferred stress-free temperature) is the exact rail temperature at which the steel experiences zero longitudinal thermal stress. Railway maintenance gangs heat or hydraulically stretch rail during laying so it reaches RNT (typically 35°C to 42°C / 95°F to 108°F in North America). This biases the rail to experience manageable compressive loads in summer while preventing excessive tensile breakages during sub-zero winter freezes.
Why are freshly tamped tracks especially vulnerable to sun kinks?
When track geometry is smoothed using ballast tamping machines, the vibratory tines break the interlocking consolidation of the crushed granite ballast stones. Freshly tamped ballast loses 40% to 60% of its lateral resistance (wL drops from ~9 kN/m to < 4 kN/m) until thousands of tons of train traffic reconsolidate the ballast shoulder. Railway rules mandate strict temporary slow orders over newly tamped curves during hot afternoons.