Snow loads included in PV design in Compress 1

[jharris3]

A couple years ago I had the opportunity to design a vessel that was installed at a facility in Alaska after the facility burned down. The schedule was tight with design, fabrication, and delivery to be achieved in 4 months.

The tower had two chambers, extra corrosion allowance for long life, and was in a fairly heavy seismic zone. Another of the requirements was to include snow loads on the platforms in the design that was 5 feet deep, and just for fun the client also wanted more platforms that were to be 24" wider than the original.

There is not any way to directly include snow loads in compress (and I don't blame codeware) so it was time to get creative.

I ended up using vertical eccentric loads to represent the weight of the snow on the platforms because these masses would then be included in the seismic weight of the vessel. I considered this to be a more severe load requirement than the appropriate load case from ASCE that would include snow loads.

The tower was not heavy to bigin with and we were to reuse the anchor bolts so the addition of 16000 lbs of snow plus some equipment on the platforms was a significant contributor to the problem.

What other ways would you have approached this problem using Compress?

 

[TomBarsh]

"J", I missed your post from months ago.

What you did is exactly what I would have suggested. There is no better solution.

There are various methods that can be used to get additional loads into the vessel model: the vertical load and lateral force from the Loads menu, specify "dummy" wind or seismic loads (but this does not give you a gravity load), enter a "dummy" component or attachment (eg: one might use the "lining" component to add the snow load...but I don't think this is a good solution myself). So the vertical loads is the way to go, in my opinion.

We have discussed adding a snow load to COMPRESS. Note that the Division 2 "rewrite" defines the loads to be applied to the vessel design. These are taken from ASCE 7 and include snow load, etc. It would seem pretty simple to add an interface ("GUI"...graphical user interface) for snow load code.

The problem with adding the snow load 'Code' is that this adds yet another layer of complexity to an already very complex program (our programmers have an awful time with the internal complexity) for probably a very minor increase in benefit. It's not only the matter of initially adding calculations for the snow load design standard (ASCE 7, and probably NBC-Canada as well) but then these have to be maintained as well each time the design standards get changed. It might be simple enough to add snow load as a user-input unit load (psf) that would be applied to the horizontal projected area of the vessel, and this may be considered.




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