| Applies To | |||
| Product(s): | AutoPIPE, | ||
| Version(s): | All | ||
| Area: | Modeling | ||
| Original Author: | Bentley Technical Support Group |
Problem:
How to apply support displacement to a support?
Solution:
| Assign displacement at a support |
There are 3 commands to add support displacement: 1. Thermal Anchor movement, 2. Imposed Support Displacement, 3.Import Impose Support Displacement values from Excel
#1. Thermal Anchor movement
Select or insert an anchor component, on this dialog are some fields to enter Thermal anchor movement (ex. Dy = 10 inch vertically up.
User should be cautioned when adding additional movements to the same node point and load case. Example, thermal anchor movement has already been assigned to anchor A00 and will be applied to load case T1 as seen above. Now if "Impose support displacement" was also assigned as shown below at anchor A00 per T1 load case (Dy = 10 inches).
what would be the expected results, that the ancor node point A00 would move 10 inches or 20 inches?
Answer: 20 inches.
First Thermal Anchor Movement was applied that caused the support to move the initial 10 inches. Afterwards, the Impose Support Displacement was added to the already displaced 10 inches for an additional 10 inches or a total of 20 inches, see the output report for A00 per load case Thermal 1:
Note, total movement report = 20 inches vertically up for Thermal 1 load case.
#2. Imposed Support Displacement
In AutoPIPE simply assign a displacement at the support for any load case, GR, T1, T2, E1, etc during modelling. Caesar has limitation of defining only 9 displacements which have to be combined in post processing to specific load cases.
a. Select Insert > Xtra data > Imposed Support Displacement...
b. The Imposed Support Displacement dialog opens
.
c. Enter in values and click OK.
These can also be applied to anchors but only act in the direction of the restraint.
Note:
1. Imposed displacement on a support is applied at the base of the support i.e. ground displacement. The force applied at the pipe is a function of the imposed support displacement in a certain direction times the spring stiffness in that direction.
2. For non-linear analysis - gaps will be considered.
Meaning, the supported pipe would not be affected until the support gaps are closed based on the amount the imposed displacement settings
Example: given the following supports
Impose support displacement = Dx = 5.00, Dy = 5.0, Dz=5.0. applied at Gravity load case.
Supports:
A02: V-stop - all gaps = 0.00
B02: Vstop - gap up = 100, gap down = 0.00
C02: Guide - all gaps = 0.00
D02: Guide - gap up and left = 100, gap down and right = 0.00
E02: Line Stop - al gaps = 0.00
F02: Guide + Line Stop - all gaps = 0.00
Question:
Which of the supports will move Dx = 5, Dy = 5, Dz = 5?
One, two, or all?
Answer:
Correct Only 1, Node point F02 is the only node point that will be displaced 5.0 in all 3 axis directions. For all the other node points, as the support moves based on imposed displacement, the support does not affect the pipe until the gap in that direction is closed. 5 out of 6 support has gaps in one or more directions that will not be closed, thus the pipe is not affected by the imposed support displacement.
3. Once an impose support displacement has been added to a load case (ex. GR) from that load case on in the load sequence (Gr - T1 - P1) the support would always be present at that displaced location when each load case was applied.
Example: Given combination GRT1P1 where impose support displacement has been assigned to T1, When analyzing load cases Gr, the support would be in it's original location. However when analyzing load case T1 and all following load cases in the load sequence, (i.e. P1), the support has been displaced to its new location based on displacement settings. However, all gaps are open and closed based on the movement of the support from the original location to the displaced location.
Question:
Will a support connected to another node point be affected by a defined impose support displacement?
Answer:
Correct, No, neither the supported location or the connected to node point will be affected by a defined impose support displacement. Why?
Because the base of the support spring is actually defined as another node point. Therefore, unless the connected to point was supported by another support connected to ground, Impose support displacement will have no affect. Consider inserting a concentrated force equal to an amount o move the pipe as needed.
#3. Import Impose Support Displacement values from Excel
AutoPIPE V8i 09.05.xx.xx has a new feature to import Impose Support Displacements from Excel: Insert> Xtra Data> Excel Support Displacement:
Using AutoPIPE's input grids a user can easily copy / paste highlighted information to MS Excel. However, the data needs to be in a certain format when copy / pasting from Excel to AutoPIPE. AutoPIPE supports the ability to transfer Imposed Support Displacements from Microsoft Office Excel, editions 2007 and later in as few as 1.2.3 steps.
1. Open Template file in Excel
AutoPIPE provided the following template files in the following folder location:
C:\ Bentley\AutoPIPE V8i SELECTseries \ Templates \ Template - Imposed Support Displacements.xls
2. Fill in the Template and save the file
The template file has some default information to be used in training new users about the feature. Highlight and clear the cells of existing information; insert your own data as needed. Once all the data has been entered, save the file (*.xls, or *.xlsx).
Note: All the Node points and Load entered into the Excel file must also reside in the model where this file is to be imported into
3. Inside of AutoPIPE, initiate the "Excel Support Displacement" command:
Select the command, Insert> Xtra Data> Excel Support Displacement.
This command will open the dialog displayed above.
4. Complete the dialog
a. Browse for the Template file to be imported
The following should appear:
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File Loaded
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The File has been successfully loaded and validated
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OK
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b. Options: (see AutoPIPE help for details about these features)
i. Change the input units as required
ii. Enable / Disable the "Override Records"
c. Press "Import" button, the following may be displayed:
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Excel Data Not Imported
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No matching record found. Hence no Imposed Support Displacement record has been overriden.
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OK
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Excel Data Imported
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Excel Imposed Support Displacement data has been successfully inserted into the model
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OK
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Pressing OK button will close the dialog and display the"Import Log Report", notifying the user of any warnings or errors found during the import process.
Note:
There can be any number of reasons which can lead to the warning messages like: Unable to Import the Excel File or The Excel file is not in the correct format. Template format file can be found in installation Directory/Templates. :
-
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- Problem with Microsoft Office / Excel.
- If you are using version above 23.00.00.230, then make sure that you have 64-bit of MS office installed in your system.
- As mentioned on the dialog, did the file originate as a copy from the "Template - Imposed Support Displacements.xls" file found in the AutoPIPE installation folder?
- Are all of the cells containing values formatted as General or as Numbers / Text?
- Are all values "Real values" within the maximum and minimum bounds of AutoPIPE?
- Is there more than 1,048,576. records trying to be imported?
- Are there blank rows?
- Does the first tab in the workbook contain all of the information?
- Are there any extra spaces in the data entered?
- Are all of the load cases and node points indicated in the model where the file is being imported to?
- Is the file extension correct
-
a. Log Messages Details:
The Record has been successfully Inserted
This record has been successfully imported into AutoPIPE's "Impose Dis." tab on the input grids.
Warning: The record is in Unrecognized format. Ignoring this Record.
There is a problem with the formatting of a cell in the Excel file on this indicated row, and therefore the data will not be imported
Example:
Processing Record Number 7 ...
B03 S2 1 4 10.5 5 4 3=
The Excel template file has 9 columns of data required for each row. In this example only 8 column of data are indicated. There is an obvious space between 1 and 4 above. Upon further inspection this value should have been set to 0 instead of leaving this particular cell blank.
Note: for each row in the Excel file there should be 9 cells of data, nothing should be left blank.
Warning: XXXXXX exceeds the Maximum limit for point name. Ignoring this Record.
As indicated by the message, this node point value in the Excel sheet violates AutoPIPE node point format. A node point in AutoPIPE can only have 4 characters, otherwise the following will be displayed:
---------------------------
Error
---------------------------
Point name can be 1-4 characters long.
---------------------------
OK
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Example:
Node point = A101234
Cell value is to large for a node point, fix issue by reduce cell information down to 4 characters or fewer, (i.e. A10)
Warning: The Specified Point (XXXX) could not be found in the model and has been ignored.
As indicated by the warning message, the indicated node point cannot be found in the model. Review both the model and Excel file for the correct node point name. The names must match exactly.
b. Fixes for "Template - Imposed Support Displacements.XLS"
AutoPIPE template file "Template - Imposed Support Displacements.xls" is used as a training tool. The following errors will occur when trying to import the file without fixing the file first:
The following fixes should be made before the file can be imported successfully:
1. Open the "Template - Imposed Support Displacements.xls" in Excel and make the following changes
a. Change Cell A4 from "A101234" to "A10"
b. In cells C6, C12, and C18 enter "0"
c. In cells D3, D9, and D15 enter "0"
2. Save file in Excel and close the application.
3. In AutoPIPE, create a model as indicated below:
a. 4 segments with following node point names (Pipe properties and node point distance are not critical, use any reasonable settings / values)
Seg A - A00 - A20
Seg B - B00 - B20
Seg C- C00 - C20
Seg D - D00 - D20
b. Select All the node points in the model and add Guide supports
c. Import Excel file as directed above.
Expected Log results: total records imported = 18, and 0 warnings / errors
Note:
1. The Import Log report is saved as an *.EIL file in the same folder as the model. This EIL file can be opened by any text editor (ie. NotePad, Ultra Edit, Ms Word, etc..).
2. New Feature (991369) was logged to add impose displacement at soil node points.
| Assign displacement at a Node Point |
Question:
Why displacements cannot be applied to a point without a support:
Answer:
Currently AutoPIPE can only apply imposed support displacements at a point which has a non-zero stiffness in the direction of the imposed support displacement. The reason, at least from static analysis stand point, is that imposed displacement is a boundary condition, pretty much the same as a support i.e. A support restricts the nodal movement to a certain value AND imposed displacement also restricts the nodal movement of a node to a certain value. Internally, the Imposed Support Displacements applied at a support are converted in to an applied force by using F = K.X, where K is the support stiffness in the direction of the imposed displacement, and X is the imposed displacement in that direction. This force then makes it way in to the Applied Force vector of the system equation described above.
Possibility of applying an imposed nodal displacement without a support:
There could be a possibility (in dynamic analysis and static analysis) to apply imposed displacements at a node which does not have any supports. Here are 2 suggestions:
Suggestion #1:
Use a trail and error approach of applying a concentrated Force at the node point in question, then check the displacements report for the actual amount of movement experienced, and vary the force as needed to achieve the proper displacement of the pipe.
Suggestion #2:
From the limited research we carried out, it seems to be known as Enforced Displacements or Prescribed Displacements. This could be then possible to apply these enforced harmonic displacements (which is determined from the response of an existing system) at a node without any support. The modal response of such a system would then correctly simulate the actual system (which potentially is not possible today as a support is required at that node). It could be possible to then determine the response of the whole system based on the imposed excitation of that node. This however would need to be researched and investigated to find an appropriate analytical solution and to couple that with the existing AutoPIPE engine.
Value of the currently available procedures:
The currently available procedure are employed successfully to determine the response of a system where the imposed displacements are applied at the point of origin of vibrations i.e. pumps. These points are otherwise rigid, hence the modal response is correct. See the earlier link from Karim with a response.
See Also
General FAQ's about Supports and Beams