| Applies To | |||
| Product(s): | AutoPIPE, | ||
| Version(s):All | All | ||
| Area: | Modeling | ||
| Original Author: | Bentley Technical Support Group |
Dec 2014, AutoPIPE 09.06.01.10
Problem:
How to model a vertical Rod (Clevis) support in AutoPIPE?
Solution:
Attention: Be sure to review, AutoPIPE help section:
Help > Contents> Contents Tab> Modeling Approaches> Modeling Approaches> Support> Rod support.
When modeling any type of support in AutoPIPE it best to understand the functionality of all the support types in AutoPIPE. Therefore please see the following AutoPIPE help section:
Help > Contents> Contents Tab> Command Reference> Component Reference >Support > Supports Overview.
Here you will see a grid of each support with relative support options, and support's Bering direction (vital information). Now that you understand this data, let us put it to work creating a Vertical Rod support.
Now, describe the support your trying to model:
1. What is the functionality of a vertical rod support?
Answer: mainly to support a pipe in the vertical direction
2. What kind of gaps does a vertical rod support have?
Answer: No gap down, may or may not have a small gap above the pipe, able to move laterally, able to move axially.
With this information add as many AutoPIPE support at the same node point to achieve this support requirement. From the online help chart mentioned above find
This support can be modeled using a V-stop or an Incline support.
Model Approach
Insert a support at the pipe node point by using the toolbar button or Insert> Support menu command. On the support dialog screen, change Support Type = V-Stop, enable the Rod Hanger check-box, modify any additional settings as needed (see online help for details on each setting), and press OK button to insert the support.
Question: Does the above modeling approach satisfy the real life support requirements at this location?
Answer: Maybe. Because, it depends on some assumptions that you are will to accept.
Question: Do you accept that the support is rigid or would you prefer to consider additional support options availnethe stiffness of the rod supporting the pipe?
Answer:
Yes, rigid assumption is acceptable
Therefore no other supports are required as a single support, V-stop, modeling approach is good enough:
a. Assumed rigid in the downward direction with gap = 0.
b. Assumed rigid in the up direction after the gap above, 0.25 inches closes.
c. Able to move lateral as the bearing direction is Vertical only.
d. Able to move axial as the bearing direction is Vertical only.
Completed modeled support will look like this:
No, prefer to consider the rod stiffness
An incline support has 4 additional features beyond a typical V-stop support
1. Enter spring rate value instead of being forced to default to rigid.
2. Consider Pendulum effect of rod swing.
3. Ultimate Bilinear Gap Force
4. Orient support in any direction about the pipe.
New set of support requirements:
Consider rod support stiffness, no gaps, able to move laterally, able to move axially, pendulum swing, and ignore ultimate force gap.
How to best model this support with the requirements above:
a. Enter weight of support
b. Enter Spring rate of rod (entering a value will affect the translation of impose support displacement, see AutoPIPE help for details).
c. Enable Pendulum and enter rod length (automatically ignores both gaps and friction)
d. Specify direction = Vertical axis.
Question: How many AutoPIPE supports are needed to model this scenario?
Answer: Again, refer to the AutoPIPE help Support table for detailed information on supports.
Given the requirements above, only 1 incline support is needed.
Modeling approach requires the user to calculate the spring rate of the rod supporting the pipe and correctly apply all of the settings in the support dialog.
Completed modeled support will look like this:
Note:
1. Analyze the system and review the results (pipe displacement and support loads) to see if the modeling approach correctly mimics the real life support. Any significant vertical movement on the support using an incline with a calculated stiffness may indicate the rod yielding and thus may require a larger rod diameter.
2. Consider Pendulum swinging motion:
Model pendulum swing of a pipe on a rod support in AutoPIPE