SCREENING TOOL ONLY. CONFIRM RESULTS WITH A QUALIFIED PIPELINE ENGINEER.
Screening tool only. Confirm results with a qualified pipeline engineer.
Buckling or collapse, local denting, soil bearing failure, existing defects or prior repairs, coating damage, ovality limits, construction configuration, and jurisdiction‑specific design‑basis requirements. These need separate engineering review.
Load share is the stress the surface load adds, divided by the room left between the pipe's stress before the load (pressure, soil, temperature) and the limit. For weld fatigue it is the cyclic stress divided by the fatigue limit. LOAD OK below 75%, CAUTION – NEAR LIMIT from 75% to 100%, WARNING – LOAD EXCEEDS LIMIT above 100%. WARNING – PIPE OVER LIMIT WITHOUT LOAD means the pipe is already over a limit before any surface load.
Screening tool only. Confirm results with a qualified pipeline engineer. This is not an engineering approval.
Static stresses follow the CEPA Surface Loading Calculator method (C‑FER; Warman, Hart et al., IPC2006‑10464). Cyclic weld checks follow API RP 1102.
The worst case is found by scanning the load across the pipe (step ≤ H/6), checking every axle line, refining the best position, and at each position scanning the crown along the pipe for the peak pressure. Distributed loads are re‑run at double grid density to report discretization error.
Deeper cover cuts the surface load's effect fast (Boussinesq pressure falls roughly with 1/H²), but the earth load is taken as the full soil prism γ·H with no arching, so it grows with depth. Below about 6 ft on a typical 42 in, 1,440 psig line the added earth load outweighs the live‑load reduction. Internal pressure (about 80% SMYS in that example) doesn't change at all, so the governing ratio moves only a few points. The Load share meter isolates the surface load so the depth benefit is visible.
The result, the simulator and the live meters use the same checks, including weld fatigue. In the simulator the fatigue range scales with the live load reaching the pipe at the current position. Each stress check is rated on load share: the stress the surface load adds divided by the room left between the pipe's before-load stress and its limit. Weld fatigue is rated on cyclic stress as a share of the fatigue limit. Load OK (green) below 75%, Caution – near limit (amber) from 75% to 100%, Warning – load exceeds limit (red) above 100%. The caution threshold is adjustable under Soil, material & limits. If the pipe is already over a limit before any load, the result is Warning – pipe over limit without load. A fatigue exceedance turns the warning on but does not change the drawn shape, since fatigue damage is weld cracking over many cycles, not crushing. The pipe stays round until a stress check exceeds its allowable, then ovalizes in proportion to the exceedance. Past 100% SMYS it shows an illustrative dent. Real calculated deflection is reported separately and is not drawn to scale.
CEPA Wheel Load Analysis equations (Technical Toolboxes) · Warman et al. 2006, IPC2006‑10464 · API 1102 live load and Ap = 144 in² · API 1102 worked calc (equation forms, SFG/SFL) · API RP 1102, 7th ed., Eqs. 5–17, Figs. 14–17, Table 3 (purchase from API).