Bi-Linear Restraints - CAESAR II - Reference Data

CAESAR II Applications Guide

Reference Data

Bi-linear restraints are used most often to model soil support where some soil ultimate load bearing capacity can be calculated. Bi-linear restraints are designated by typing a 2 immediately after the direction in the restraint Type box.

After a bi-linear spring is entered, the restraint options change as follows:

  • Stif changes to K1, which is the initial stiffness. A value for K1 is optional. If it is left blank, the software presumes a rigid initial stiffness.

  • Gap changes to K2, which is the yield stiffness. The software requires a positive value for K2.

  • Mu changes to Fy, which is the yield load. The software requires a value for Fy.

Some sub-sea pipeline resistance tests have shown that load carrying capacity drops after the ultimate load is reached, and displacement continues.

For more information about the use of the spring types used to model underground piping systems, see Underground Pipe Modeler in the CAESAR II User Guide.

Characteristics of Bi-Linear Supports

Pipe in a Trench Bi-Linear Restraint Modeling

Estimated Stiffness Models