Comments

• disla

  January 16

  From Mecway Manual:
  
  "On a shell element, the face is offset from the midsurface by half the element thickness so a traction applied to the face generates moments at the nodes as well as forces.
  If you don’t want these moments, apply it to the elements instead of the faces. Then it acts on the midsurface. You should always do this for curved shells with the CCX solver because those moments usually include a normal component which isn’t allowed by CCX."
  
  I have try to apply the traction to the elements and it works. The problem probably is on the moments introduced into the sloped shells.
• Andrea

  January 20

  Hi!
  Hi had a little experience with silos and I encountered problems with leg joints, wind and local buckling (EN1991-EN1998 loads for seismic actions). Less problem with discharge loads, but could depend from type of bulk material.
  If you are working on a complete project let me know
  Regards
  
  
  
  
• Mishal

  January 23

  In the past I have calculated these loads to verify some of the data we got from BHM engineers, however we still used the data they provided. In almost all instances the data regarding loads Pt and Pw would be left out of there reports for some reason. I have only had a few instances where the loads were critical, as Andrea mentioned issues arose from other aspects.
• disla

  January 23

  Thanks both,
  
  This model came up in a different Forum. I found it a good opportunity to try it and see which could be the drawbacks.
  I have experience with Liquid and Gas storage, but powder /solids storage are a completely different world although they may look similar from the outside.
  I have finished my Excel file to compute the different product loads, and I have applied them one by one and separately to the model.
  When combining them one must be careful applying all of them in a Global coordinate system. Not a big deal but certainly larger expressions for unsymmetric loads patterns.
  Pressures (DLOAD/DSLOAD) are transformed to *CLOADS which are affected by Transform cards around.
  
  As a quick number pwf = μ phf. Friction coefficient depends on the Silo wall surface and Product. Values could be found in EN 1991-4 Table E.1.( μ arround .22 - .77)
  That means vertical traction can be as much as a 77% of Normal pressure. That introduces a new compressive Buckling mechanism not present in Pressure vessels or Tanks under Hydrostatic pressure.
  Note the code says :” The stiffness of the particulate solid should not be assumed to provide additional stability to the silo wall or to modify the loads defined within this standard”
  This new to me buckling mode due to product friction on the walls seems real.
  
  
  
  By the number of loads involved, asymmetries and extremely large D/t ratios , I anticipate solving the silo as a whole FEA project very complex.
  Probably it’s more suitable to solve specific details like transition and supporting area.
  
• MMK66

  January 23

  Enter FEA https://enterfea.com/pl/
• barmin

  January 25

  I second EnterFEA - we deal with silo on a daily basis (in AS and EC standards) and also solve them using the full GMNIA procedure described in EN 1993-1-6 so it's doable without much problems.
• disla

  January 26

  Thanks both, knowing others have solve the problem is encouraging. ¿Are you solving with ccx / mecway solely or do you get some support from other FEA tools?
• barmin

  January 27

  I use Strand7 as main solver, as ccx doesn't support "real" shell element and also doesn't have any form of Riks/Crisfield (arc-length) algorithm which is crucial to track stability of such structures.
• Mishal

  January 28

  @disla If you want a book that gives a basic outline of doing this with predominantly hand calculations pop me a message with your email address and I will share some information.