04. Modeling Tie/Link supports in AutoPIPE

Applies To
Date Logged
& Current Version
Jan. 2019


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

There are 2 options to consider the arc / pendulum swing in AutoPIPE

1. Tie/link

2. Incline support, Enable Pendulum

Option #1: Tie/Link Support

Note, that 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.  


Option #2: Incline Support - Enable Pendulum

AutoPIPE and higher had a new feature added, Enable Pendulum setting on the Incline Support dialog. When checked, the program will move the supported piping point in a circular arc about the pivot point defined by the direction of the support and rod length.

When the support is connected to Ground and this option is checked, the program will enable the Rod length field for the user to manually enter the rod length (the length from the supported piping point to the pivot point). The Auto check-box would remain disabled in this case. 

When the support is connected to another piping or beam node in the model, the program will enable both the Auto check-box as well as the Rod length input field. The user can then either enter the rod length manually or enable the Auto check-box for the program to automatically calculate the rod length using the supported piping point and the connected point. The Rod length input field is grayed out and closed for input when the Auto check-box is checked. In cases where the user updated the Connected to field from a node in the model to Ground, the program will un-check and disable the Auto check-box and enable the Rod length field for manual input while retaining the last calculated value.

When compared to a tie/link support, the Enable Pendulum setting will not allow the user to enter gaps values, these fields are greyed out and values set to zero.  

See Also

Flexible Joint - Modeling Approaches, Tips, Techniques

Different Types of Supports

Bentley AutoPIPE