Wind Loads on mostly enclosed vessels ASCE 7-10

[ads0221]

I'm looking for some justification in our modeling of wind loads with respect to a few existing vertical vessels.

We have an existing rectangular industrial building with 3 floors. The first floor at grade is completely open...the second and third floors are completely enclosed with girts and purlins besides (1) little 2'-0" opening at each level for visibility access when walking (over 85% of building enclosed at these levels).

There are a couple of reactors, slurry tanks, heat exchangers on each level we're trying to properly model with existing loads for the clients as they begin to look at rearranging some equipment. In my engineering judgement these vessels will not see but 25-50% wind gusts relative to open conditions. I haven't found any excerpts from ASCE 7-10 Chapter 29.5 with respect to partial loading of non-structural equipment. Where this site is located even dropping down from an Exposure Cat C to B is overkill in my judgment. Is Chapter 29.8 "Minimum Design Wind Loading" 16lb/ft^2 something that wouldn't be too extreme in underestimating?

 

[JStephen]

If the vessels themselves were specified to be "inside a building", they may have been designed for zero wind. Details beyond that are often poorly communicated to the vessel designers.
Somewhere in either AISC or IBC (Edit: IBC 2015-1607.14) is a requirement that interior walls or partitions be designed for 5 psf, and that is sometimes applied to vessels or tanks in an enclosed building.
On the open bottom story, I would be inclined to figure full wind for anything in there, or possibly higher-than-full-wind to allow for channeling through there.
On upper stories, not so clear as you mention. I would probably assume normal wind exposure unless that caused problems elsewhere in the analysis.
Also compare to notional or seismic loads.