Expansion Joint / Bellows
- Darrell
Define menu>Components>Expansion joints. CSiPlant expansion joint component offers integrated options to model tie rods with or without gaps, effective inside diameter area for consideration of pressure thrust, and options to apply linear or multi-linear breakaway stiffness values in each direction. Quick-model options for hinge and gimbal joints.
Integrated tie rod modeling with tension and compression gap options enable users to quickly create comprehensive expansion joint models for more realistic analysis calculations without being required to add time-consuming Cnodes or tie-link elements which have separate output results. In the expansion joint dialogue users can click the pull-down arrow at 'Expansion Joint data' to reveal tie rod and other integrated modeling options as shown in the screenshot below.
Users can define and reuse expansion joint components in their model without having to reenter data each time.
In each direction users can specify Rigid, Simple (linear spring), or Advanced multilinear plastic spring stiffness. The Advanced option enables users to define multilinear force/displacement and moment/rotation relationships to specify allowable movements in each selected degree of freedom, making it also suitable for modeling ball joints, couplings, telescoping slip joints, and flexible hoses among other applications. Please note that rotational stiffness is entered using radians, with no current option to enter in degrees.
Directional stiffness properties are applied in local axes. Expansion joint local axes are the same as the connected piping and can be displayed using the 'Set display options' 
. Pipe and expansion joint local axes shown below.
Expansion joint local axes are the same as piping local axes, displayed below in line view with colored arrows. Red arrow points to local +1 (U1) longitudinal direction, green arrow points to local +2 (U2) which is vertical with horizontal piping, and blue arrow points to local +3 (U3), so R1, for example, would be torsional stiffness. The same colored arrow convention with red local 1, green local 2, and blue local 3 can be displayed for local axes of supports, joints, frames, and local axes of links.
Convoluted modeling approach required by other pipe stress software:
