How to model Tie/Link supports correctly in AutoPIPE?
When Tie/Link is entered in the Support type field, the Support dialog is updated to include additional fields. If friction is not present, the connected points are restrained only in a direction towards or away from each other. Friction provides restraining forces normal to this direction. A tie/link may be used to model a pipe hanging from another pipe, a pipe supported by a beam member, it may be used to simulate the tie rods of a bellows (flexible Joint) and modeling a sway strut support (see AutoPIPE help section below):
Help > Contents> Contents Tab> Modeling Approaches> Modeling Approaches>
> Supports> Model 3: Rod Support
> Flexible Joints> Tied Bellows Expansion Joint
> Support> Model 6: Sway Strut.
The most important aspect to remember is the direction of a support's bearing spring. See AutoPIPE help for "Support", this page shows a detailed grid of information about each support available in the program: bearing directions, gaps, stiffness, Spring rate, etc.. After reviewing this chart and all the footnotes it will become clear that a Tie/Link bearing spring direction is always defined by the connected points. Therefore only movement along the axis of the bearing spring are restricted (baring any Gaps, Friction, and Spring rate settings).
ARC / Pendulum Swing
As of Jan 2019, AutoPIPE does not have a support component that maintains a rigid length between node points while one point is swinging / rotating relative to the second node point. The bearing spring for a Tie/Link support is only in the axis direction between the 2 connected points. Another words, the axis drawn by Tie/Link support between connected points will be maintained barring any gap settings. Gap settings may allow the node points expanding or contraction movements along this axis direction.
Think of a it this way, a Tie/Link support is drawn between 2 node points (ex. A01 and A04), now draw an imaginary plane perpendicular to this axis at each node point.(ex. Red lines in image below)
Depending on the gap settings,
a. All Gaps = 0, node points can move anywhere on their respective perpendicular planes, but cannot not move farther apart nor closer together.
b. Gap Forward = xxx & Gap Backwards = 0.00, this configuration allows the node points to move a total of xxx distance closer to each other on the established axis direction, and once the xxx gap is closed, the support becomes rigid again.
c. Gap Forward = 0.00 & Gap Backwards = xxx, node point can move a total of xxx distance away from one another on the established axis direction, and once the xxx gap is closed, the support becomes rigid again.
Examples:
Flexible Joint - Modeling Approaches, Tips, Techniques
Different Types of Supports
Bentley AutoPIPE