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*PIP Connection

Purpose

To define pipe-in-pipe connections between nodes of the finite element model.

Theory

Refer to Standard Connections and Sliding Connections for further information on this feature.

Keyword Format

The keyword begins with a number of optional lines to specify miscellaneous parameters. This is followed by various types of line that may be mixed and repeated as often as necessary.

Optional line to specify whether the orientation of the pipe-in-pipe connections is based on the instantaneous positions of the connected nodes or their initial positions.

[ORIENTATION=Orientation]

Optional line to specify that bandwidth optimisation is to be performed every time a pipe-in-pipe connection changes due to relative motion of the connected pipes in the axial direction (sliding).

[BANDWIDTH=UPDATED]

Optional line to monitor for occurrences of relative penetration at pipe-in-pipe connections. A warning is issued during the analysis if penetration exceeds a user-specified threshold.

[PENETRATION_TOLERANCE=Penetration Tolerance]

Line defining an explicit nodal connection:

Primary Node (Node or Label), Secondary Node (Node or Label), STIFFNESS=Stiffness or CURVE=Curve Name

Line defining multiple nodal connections:

GEN=Primary Start Node (Node or Label), Primary End Node (Node or Label) 

[, Increment], GEN=Secondary Start Node (Node or Label), Secondary End Node (Node or Label) [, Increment], 

STIFFNESS=Stiffness or CURVE=Curve Name

Line defining an explicit nodal connection, capable of modelling sliding contact:

Primary Node (Node or Label), SET=Secondary Element Set, 

STIFFNESS=Stiffness or CURVE=Curve Name [, AXIAL_STIFF=Axial Stiffness or AXIAL_NONLINEAR=Axial Curve Name]

Line defining multiple nodal connections, capable of modelling sliding contact:

GEN=Primary Start Node (Node or Label), Primary End Node (Node or Label) 

[, Increment], SET=Secondary Element Set, STIFFNESS=Stiffness or CURVE=Curve Name 

[, AXIAL_STIFF=Axial Stiffness or AXIAL_NONLINEAR=Axial Curve Name]

Orientation may be either INSTANTANEOUS (the default) or INITIAL. If you specify a node label rather than a node number, it must be enclosed in {} brackets. A Stiffness is specified when the connection between the pipe-in-pipe sections is linear, whereas a Curve Name is specified when the connection is non-linear. Resistance to relative axial motion may be characterised by a linear Axial Stiffness or a non-linear Axial Curve Name. If a curve name is specified, then the curve must be defined using *PIP STIFFNESS. Increment defaults to 1.

Miscellaneous Options

Purpose

To define miscellaneous options relating to pipe-in-pipe connection modelling.

Table Input

Notes

(a)If you wish to check contact based on the actual pipe diameters, you should specify a penetration tolerance of zero. Given the numerical model of the pipe-in-pipe connection, power-law curves for example, you may wish to tolerate small levels of penetration, in which case you should specify a small, positive value for the penetration tolerance. If you wish to suppress the warning messages altogether, you should specify an arbitrarily large tolerance. The tolerance parameter may also be used to provide an indication of the connected pipes approaching contact, via the specification of a small, negative tolerance value.

Standard PIP Connections

Purpose

To define standard pipe-in-pipe connections between individual nodes of the finite element model.

Table Input

Notes

(b)Refer to Standard Connections for further information on the significance of the inputs supplied here.

(c)If a non-linear force-deflection curve is specified for the connection stiffness, then the actual curve must be defined in the Pipe-in-Pipe Stiffness - Data Pairs or Pipe-in-Pipe Stiffness - Power Law tables.

Standard PIP Connections - Generate

Purpose

To generate standard pipe-in-pipe connections between groups of nodes of the finite element model.

Table Input

Notes

(a)Refer to Standard Connections for further information on the significance of the inputs supplied here.

(b)If a non-linear force-deflection curve is specified for the connection stiffness, then the actual curve must be defined in the Pipe-in-Pipe Stiffness - Data Pairs or Pipe-in-Pipe Stiffness - Power Law tables.

Sliding PIP Connections

Purpose

To define sliding pipe-in-pipe connections between individual nodes of the finite element model.

Table Input

Notes

(a)Refer to Sliding Connections for further information on the significance of the inputs supplied here.

(b)If a non-linear force-deflection curve is specified for the connection stiffness, then the actual curve must be defined in the Pipe-in-Pipe Stiffness - Data Pairs or Pipe-in-Pipe Stiffness - Power Law tables.

Sliding PIP Connections - Generate

Purpose

To generate sliding pipe-in-pipe connections between groups of nodes of the finite element model.

Table Input

Notes

(a)Refer to Sliding Connections for further information on the significance of the inputs supplied here

(b)If a non-linear force-deflection curve is specified for the connection stiffness, then the actual curve must be defined in the Pipe-in-Pipe Stiffness - Data Pairs or Pipe-in-Pipe Stiffness - Power Law tables.