raising metal building

huangyhg

raising metal building
hi,
i have a client who wants to add a second floor to an existing metal building.  however, the existing metal frames need to be raised about 5 feet in order to allow for adequate headroom.  the frames consist of wide flange constant width columns, and tapered beams that frame over the columns, the beams are spliced in the middle.  the building is about 40 feet wide, and the frames are spaced about 24 feet o.c.  
my solution is to raise the frames onto new 5 foot high concrete piers that would be adequately anchored to the existing piers to resist any lateral loads.  the base plate connection will be designed for the appropriate loads and moments.  
the new floor load will be completely independent of the existing framing since i am planning on adding new beams and columns inside of the existing frames.
i will also have to check the seismic adequacy of the building since i'm adding a considerable dead load.  
i just wanted to see if anyone thinks that there's something else i should be worrying about besides the issues i mentioned above.  i've never done this kind of project before and i wanna make sure i'm not overseeing something obvious.  thanks.
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i've raised the roof of an existing metal building and it is a little tricky.  metal buildings are designed pretty close to the material limits.  when raising a building you incresase not only the dead load on the footings, but the wind loading on all the building components. so, make sure you look at all the lateral loads and bracing.
having straight columns makes it somewhat easier.
i would be a little concerned about the flexibility of the piers. to resist the thrust from the metal building columns, the piers must deflect laterally. this movement will, in turn, lessen the amount of gravity load that the frame can resist. the pemb frame is not designed to be supported on a yielding support.
butler and nucor have some good information on metal building system mezzanines, but...
did you consider stand-alone mezzanines?
i am actually contacting butler to see what options i have.  thank you all for the responses, they've been very helpful.