Upheaval Buckling of Buried Long-radius Bend Analysis

Read about START-PROF pipe stress analysis software

Related Topics

1 - Pipeline, 2 - soil surface


Note that increased laying depth and backfill soil density positively effects stability, since the soil keeps the pipe from buckling.

Due to this, overload factors for soil, pipe, insulation and product weight are automatically set as less than unity. If bend radius is increased, critical forces are increased, but also "self-compensation" ability is decreased, which increases equivalent forces. Therefore, exact recommendations for changing the initial bend radius to increase stability cannot be given. A certain middle value must be found by changing various properties and running several test analyses. For more information, see bend stability analysis methods.

Several conditions are checked:

Input data can be copied using the toolbar icon and  inserted into any other Start-Elements analysis by using the toolbar icon in that file.

Input Data




External diameter, D

External pipe diameter, D

Pipe wall thickness, S

Nominal wall thickness

External casing diameter, Dc

External insulation casing diameter. If insulation is absent, set as 0

Ambient temperature

Average wall (metal) temperature at the time when pipe segments become a single joined structure. More...

Design temperature

Design temperature. More...

Depth, Z

Depth (distance from soil surface to pipe axis)

Bend radius, ρ

Element bend radius

Angle of horizontal slant, φ

Angle between the plane passing through the bend and the plane passing through the curve peak and perpendicular to the vertical plane

Turn angle, α

External angle between straight elements adjoining the bend

Uniform pipe weight

Pipeline and adjoining equipment uniform weight. More...

Uniform insulation weight

Uniform insulation weight. More...

Uniform product weight

Uniform product weight. More...

Backfill soil number

Trench soil number, can be selected from the soil database (see appendix 1 below)

Base soil number

Base (undisturbed) soil number, can be selected from the soil database.

Design pressure, P

Design pressure in operation state. Set for all standards except SNIP 2.05.06-85. More...

Operation pressure, Pop

Operation pressure (based on standards). Set when analyzing with SNIP 2.05.06-85. More...

Steel brand

Pipe material from the materials database

Insulation type

Insulation type: armopenobeton, polymer, polyurethane, other


After analysis, the maximum value of stability margin K is displayed. Stability conditions are considered to be met if  K 1.

Menu Access

Pipe. Buried > Long-radius Bend Stability