Out-Of-Straightness (OOS) for under-straight pipe

Target radius of curvature: R [m]

Target curvature: 1/R [1/m]

Nominal strain: (OR-t/2)/R (ABAQUS) or OR/R (Orcaflex)

Pipe length to measure OOS: L [m]

Angle: φ = L/R [rad]

OOS over a Lm length:

OOS = R*(1-cos(φ/2)) [m]

= R*2*(sin(φ/2)^2) [m]

approximation-1 ~ R/2*(φ^2) [m]

approximation-2:

The target out-of-straightness (OOS) over the measured pipe length of Lm is calculated as the following formula, where the target residual radius of curvature is RT:

OOS = RT – sqrt(RT^2 – Lm^2/4)

TRUC: total residual unloaded curvature