The following is based on the following AutoPIPE's help section: 

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Frames: Pipe Rack Modeling Examples

Frame structures are commonly used to support piping systems. In most cases, the structure is assumed to be much stiffer than the piping itself and can be modeled simply as a rigid support. However, AutoPIPE also allows a supporting frame structure, such as a pipe rack, to be included in the system model.

The following models depict a system of parallel pipe runs (shown in the figure) which are supported by a pipe rack structure. The pipe-frame connection type varies with each model. The piping system is usually defined first as this simplifies the modeling of the frame that supports the pipes.

Three methods for modeling pipe racks are provided below:

Pipe Rack (Method 1): 

Each piping point is connected to a corresponding beam point using a two-point support (tie/link).

Pipe Rack (Method 2):

A pre-defined directional support at each piping point can be connected to a single beam point. This model takes advantage of the fact that a V-stop always restricts the movement of a point in the vertical direction irrespective of the location of the Connected to point. This simplifies the modeling of the frame itself as definition of all connection points are not necessary. However, all of the support reactions are transferred to the one beam point rather than their actual locations (directly beneath each piping point).

Pipe Rack (Method 3):

Each piping point is connected directly to a corresponding beam point. This model represents a rigid connection between the pipe and beam member.

Comments, Questions, and Answers on Frames: Pipe Rack Modeling Examples:  

1. What modeling method and support type should be used for pipe U-bolted on a rigid beam?

Answer: 

First ask yourself what type of AutoPIPE support(s) are required to mimic the actual support. AutoPIPE allows the user to place one or more supports at a node point to mimic an actual support. How is the pipe restrained / allowed to move in this image above?

1. Pipe cannot move down, because of resting on beam that is rigidly supported.

2. Pipe cannot move laterally because of U-bolt (assume no gap).

3. Pipe cannot move Upward because of U-bolt (assume no gap).

4. Pipe can move axially through the support with some amount of friction. 

Open the Support dialog and press the HELP button, the following grid of information will be displayed for reference:

Bearing Direction refers to what axis a support's stiffness will act in. Example, V-stop bearing direction is Vertical only. Therefore regardless of  a V-stop orientation, it would only resist vertical movement of the pipe node point because the bearing direction is what, correct: Vertical only.

In this example above, what options are available that meet all 4 criteria for bearing directions:

Option #1, Use 2 supports: 1 - V-stop and 1 - Incline, the V-stop will resits any vertical movements while the incline can be set to resist any lateral movement.

Option #2, Use 2 Supports: 1 - incline on the vertical axis and 1 - incline on the horizontal lateral axis.

Option #3: Use 1 support: guide.

Option #4: Use 2 supports: 1 - tie/link on the vertical axis and 1 - incline on the horizontal lateral axis. 

Q. What modeling method and support options should be used?

A. There are 3 choices

Choice #1: use Pipe Rack (Method 1), however this will limit your support option to only #4.

Choice #2: use Pipe Rack (Method 2), all of the support options would be suitable, however suggest option #3 as it only has a single support  

Choice #3: model only the support using support option #1, #2, or #3 without modeling the frame work.

2. What modeling method and support type should be used for pipe resting on a rigid beam?

Answer: 

Using the same philosophy as before, How is the pipe restrained / allowed to move in this image above?

1. Pipe cannot move down, because of resting on beam that is rigidly supported.

2. Pipe can move laterally because of U-bolt (assume no gap).

3. Pipe can move Upward because of U-bolt (assume no gap).

4. Pipe can move axially through the support with some amount of friction. 

In this example above, what options are available that meet all 4 criteria for bearing directions:

Option #1, Use 1 supports: 1 - V-stop

Option #2, Use 1 Supports: 1 - incline on the vertical axis

Option #3: Use 1 supports: 1 - tie/link on the vertical axis 

There are 2 choices

Choice #1: use Pipe Rack (Method 1) with support options #3.

Choice #2: use Pipe Rack (Method 2), all of the support options would be suitable, however suggest option #1

Choice #3: model only the support using support option #1 or #2 , without modeling the frame work.

See Also

Modeling Approaches

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