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Recent content by Nick7805

  1. Nick7805

    Supported Tank Roof - Laterally Braced Rafters

    HTURKAK, yes it an internally column supported roof design. Some images of the bracing system are attached for clarity. In these images, MK 12 is 1/4"x2" flatbar. JStephen, could you please elaborate on the case where all rafters move the same way? Is this a lateral buckling case you're...
  2. Nick7805

    Supported Tank Roof - Laterally Braced Rafters

    I'm working on a design for an internal raftering support system for a 120ft diameter API-650 tank. I'm looking at a lateral bracing design for the rafters - I've reviewed some of our old projects, and we've always provided lateral bracing to internal raftering systems by welding 1/4" flat bar...
  3. Nick7805

    Non-Linear Convergence

    @ThomasH About contact stabalization: "Surface contact solution stabilization option. When set to ON, will generate stabilization spring stiffness via the model parameters NLKDIAGSET, NLKDIAGAFACT, and NLKDIAGMINAFACT on the contact boundary." Yes I agree! I hope it will solve my problem...
  4. Nick7805

    Non-Linear Convergence

    @ThomasH I agree with you, I didn't mean to imply it was a solver issue with what I said. I don't have much experience and not very much help.
  5. Nick7805

    Non-Linear Convergence

    @ThomasH I am also sure the structure isn't overturning. I don't really see why you say the structure is weak at the base nor why that would cause my convergence problems, considering the problems have been occurring at a load level of <1%. Perhaps the frequencies should drop; but it's hard for...
  6. Nick7805

    Non-Linear Convergence

    @rb1957 I don't disagree with your sentiments about Inventor Nastran. I think it's designed to be so user friendly that it may often lead to misuse among beginner to intermediate FEM analysts. It also has some major limitations to its usability since more advanced features are either hidden or...
  7. Nick7805

    Non-Linear Convergence

    @rb1957 Autodesk Inventor has no simple way to allow that level of control, but I could do so by manually writing and adding cards into the bulk data file. There's also no easy way to to determine which nodes belong to a single face in a complex model, but I think I could figure out how to do...
  8. Nick7805

    Non-Linear Convergence

    Thank you for all your suggestions everyone. I'm applying what I can to my model and learning a lot reading about these different things. Unfortunately, I'm not able to apply the quasi-static analysis, as Autodesk Nastran won't allow edge-to-surface contact types in dynamic analyses. In regards...
  9. Nick7805

    Non-Linear Convergence

    @rb1957, yes I can make the ground as wide as I want. The only limitation is the number of nodes it adds to the analysis. Do you think this could be hindering convergence? I'll make it wider and run another simulation.
  10. Nick7805

    Non-Linear Convergence

    @rb1957 as I mentioned to FEA_Way, these structures are left unanchored more frequently than they're anchored. Because of that, I'm not using bolts in the analysis. Before I answer, what do you mean by the limiting size? And are you referring to the gradient up the sides and the bottom of the...
  11. Nick7805

    Non-Linear Convergence

    @BlasMolero, thank you for your detailed reply. I will look more into using gap elements; I know it's possible in Inventor Nastran, however so far I've been unable to find info on how to assign them. From what I understand, you can assign a stiffness for gap elements? @rb1957 yes there is a...
  12. Nick7805

    Non-Linear Convergence

    Thank you for the reply Blas and FEA. @BlasMolero I have a parameter for contact stabalization set on in Inventor Nastran called "CONTACTSTAB". I'm unfortunately not able to post the model. @FEA_Way It's not true that they are fixed to the ground, they really do often freely sit upon the...
  13. Nick7805

    Non-Linear Convergence

    I'm trying to model a silo with a hopper (shell elements) resting against the ground (solid elements) using Inventor Nastran. In my current model, the ground has significantly lower stiffness than the hopper base and there is a separation contact defined between them. There is also various...
  14. Nick7805

    Modelling a Soft Ground

    Thank you for taking your time here human909, I appreciate it very much. These bins are for grain and fertilizer storage. And yes, the modelling reflects the design, which has been being used for a long time. When you say lateral bracing, are you referring to bracing in the radial direction, or...
  15. Nick7805

    Modelling a Soft Ground

    Hey @human909, So my job is to model a hopper bottom silo with non-linear FEA with loads calculated as per EN 1993-4-1, and optimize the components to reduce material costs. The hopper/silo is supported the last few meters by legs. I'm new to the industry and happy for advice and suggestions...
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