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...
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...
@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...
@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...
@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...
@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...
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...
@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.
@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...
@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...
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...
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...
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...
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...
I agree with you Bkal, except for the fact there's contacts set with other components in the structure that connect to the base. I believe that these should cause some stress in the base regardless of the rigid body constraint -- but I won't know for sure until I get to that point.
I'm going to...
Hi Bkal,
The purpose isn't to design a foundation as the structure simply sits on the ground. The structure is a silo and I'm interested in knowing the stress in the metal base of the silo. If I didn't model the ground and instead fixed the base in my simulation, I wouldn't find the stress in...
Hi bkal,
The point isn't to analyze the foundation, it's to analyze the structure that rests on the foundation while accounting for the support the foundation provides to the base of the structure. In this case, I don't see a big issue. However, despite this, I think that this method of using a...
Thank you for the suggestion FEA way, but I believe that's not possible on Inventor Nastran. The closest option is a spring connection, but that only allows for point-to-point connection, yet I have an entire base surface. Do you have any other suggestion?
