Custom Expansion Joint / Internal Support

Related Topics

Custom expansion joints are modeled with any combination of internal linear and rotational restraints in a node connecting pipe ends, which are removed and replaced with elastic restraints with a given flexibility in order to allow freedom of movement in a certain direction. In fact, it is internal restraint between two pipes, that is connecting one pipe to other using rigid or elastic restraints.

By default, if no restraints are input for a custom expansion joint, pipe ends are considered to be rigidly connected, i.e. having six rigid restraints (three linear and three rotational). Next, desired internal restraints are deleted and replaced with restraints with an input flexibility.

A maximum of three linear and three rotational restraints can be set in a custom expansion joint. The following rotational and linear restraints can be used:

To create a custom expansion joint:

  1. Select the node

  2. Choose the menu option Insert > Expansion Joint > Custom EJ or use the toolbar icon.

A dialog window will appear (fig. 1).

Fig. 1. Custom expansion joint restraint properties. Linear restraint along the Y axis and rotational restraint around the X axis are free. Both of these restraints are replaced with elastic springs with a certain flexibility




Element name. If checked then it shown in 3D view

Thrust area

Thrust area is input to account for pressure thrust force. Thrust area must be input only for expansion joints with elastic restraints along the pipe axis. In other cases, it will not be used in the analysis.

Restraint type

Two types of restraints are possible: rigid and elastic. Direction is calculated automatically for rigid restraints and need not be input.

Loc. axes

If the local coordinate axes flag is not checked, coordinates are set as global (X,Y,Z); if it is checked, coordinates are local (Xm,Ym,Zm). All restraints must be mutually perpendicular.

When "other" is selected, any desired restraint direction can be selected

Restraint direction is modeled with three angles between restraint direction (vector) and global coordinate axes.  Minutes are written as tenths of a degree (up to two digits). For example, an angle of 30.25 indicates 300 15'. "+" is not written for positive angles.  More...

Restraint direction

Direction in which mutual displacement or rotation of pipe ends is restricted


Flexibility of an elastic restraint

More details on restraint types can be found in "custom expansion joint restraints" and "custom restraints".

Expansion Joint analysis results can be found in Expansion Joint Deformation Table.

Menu and Toolbar Access

To insert a custom expansion joint, select the desired node and use the menu option: Insert > Expansion Joint > Custom EJ

or press the toolbar icon.

To view ballasting weight properties: