| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Area: | modeling |
| Date Logged & Current Version | Oct 2023 23.00.00.230 |
Problem:
What options are there to apply a wind load to a vertical tower / vessel using AutoPIPE?
Solution:
Here are the options to model a Wind load on a Vertical Tower / vessel that has piping.
Option #1: Model Vessel / Tower using pipe properties
If the vessel / tower is constructed of a large diameter circular shell, suggest adding one or more new pipe property to account for the tower/vessel size, stiffness, density, etc.. Insert a new segment starting at the base of the vessel / tower, modeling up. Make sure to add an rigid / flexible anchor at the bottom of the vessel / tower to properly support it by the ground / concrete foundation. Next apply a wind load to this and other segments above the ground level or outside of the vessel / tower shell. Another word, any piping below the wind ground level specified or inside the envelope of the vessel / tower shell should have no wind load applied.
Connect piping to the vessel / tower using supports as needed. Finally Analyze the system.
The analysis will apply the wind load to the tower / vessel based upon the pipe properties used.
Option #2: Model Tower using Beams
If the pipe is supported by a tower constructed by beam sections. Then model the structure using beam sections anchored to the ground.
Note:
When "Apply Wind load" option is enabling on the Beam dialog or Beam tab of Review Component Data grids for each structural member, wind loads defined are applied to that structural member. When disabling this check-box, wind loads are ignored for that structural member.
Next apply the Wind load case with the correct ground elevation. Finally analyze the model.
Option #3: Model Wind load using Impose Support Displacement
Manually calculate the amount of movement at the support locations, and insert "Impose Support displacement". Note the Insert Support Displacements command can only be placed at a node point where a support / anchor is located. Furthermore, this displacement is applied to the base of the support spring. If the support stiffness is anything other than Rigid, the support will not move the full distance specified by the "Imposed support displacement" setting. The support / anchor stiffness will be taken into consideration.
Important:
The impose displacement can only be applied in a support bearing direction. Appling the impose support displacement setting in a non-bearing direction will have no affect.
In addition, imposed support displacement will only affect a pipe when the support gap has closed; a. due to load sequencing, or b. performing a Linear analysis.
Example:
Consider a rigid guide support, gaps closed, on a pipe where "Imposed support displacement" is applied in the pipe's axial direction.
Question: Will this impose support displacement affect the guide support? Yes or No.
Answer:
Open the support dialog, press the Help button in the lower right corner of the dialog, and review the support table indicating bearing directions for all of AutoPIPE's supports. Notice that a guide support bearing direction is Perpendicular to pipe (vertically up / down, and laterally left / right). Therefore the impose support displacement setting would be applied parallel to the pipe, thus no movement will be applied to the pipe because support there is no bearing direction parallel to the pipe axis.