We occasionally see models upwards of 4,000 elements. While we definitely do not encourage this model size, it is possible from a computational point of view to create and analyze much larger models with no loss of accuracy in the results.
But there are some very real problems with large model sizes. First, it is difficult to render such large models in the plot utility. The new HOOPS Graphics engine is quite memory intensive and for large models you may need a serious upgrade to your computer's video card to speed up the rendering. Also in the plot, with so many elements, it is difficult to display all the information such as restraints and node numbers. You will be forced to zoom in on small sections of your model to view any significant detail. However there is a search feature in the graphics that allows you to find specific elements rather quickly. I think as future improvements to our graphics capabilities come online you will be able to more effectively view these larger models in the plot.
The second concern with large model sizes is human limitation. It is simply easier to make a mistake on a larger model and not catch it during your review process. Fatal errors, especially the dreaded coordinate mismatch can be very difficult to track down in a large model. And although everyone knows they should back-up their work, I have had at least one case where a 4,000 element model had become corrupted and there was nothing that could be done to recover the data. This engineer had to start from scratch re-creating this model!
One mathematical limitation occurs with huge models containing many nonlinear restraints (such as all the +Ys I assume you use in modeling your pipe rack). The more nonlinear restraints and friction you have in your model, the more likely it will be to not converge on a solution. Then you will have the task of changing friction tolerances or even modifying restraints (linearizing a few of them usually does the trick). In a large model this modification of restraints can become a real pain.
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Loren Brown
Director of Technical Support
CADWorx & Analysis Solutions
Intergraph Process, Power, & Marine
12777 Jones Road, Ste. 480, Houston, TX 77070 USA