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RE: Net uplift on joists and joist girders

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Title: RE: Net uplift on joists and joist girders

The net uplift that the joist fabricator needs to design the joists and the bridging is the gross uplift minus the portion of the dead load that includes the dead load superimposed on the joists (deck, insulation, roofing, etc.) and the weight of the joist themselves.  It does not include the dead load of the joist girders, since this load does not help the joists resist uplift.  I usually only include a portion of the assumed MEP dead load, since we tend to assume these values on the high side.

I've had significant uplift pressures on buildings in coastal areas, where the wind loads are high.  This is especially true when the architect uses a very light single-ply roofing system.

-- Joel

Joel Adair, EIT
Halff Associates, Inc.
E-mail: jadair(--nospam--at)

-----Original Message-----
From: Alden Manipula, E.I.T. [mailto:amanipula(--nospam--at)]
Sent: Wednesday, January 16, 2002 11:17 AM
To: SEAINT Listserve
Subject: Net uplift on joists and joist girders

Net uplift is the difference between the calculated pressures on the roof
structure and the roof dead loads, right?

And if so, when does it become a problem?  Most of the buildings i've done
so far have been relatively small and the roof dead loads have always
exceeded the pressures i've calculated.


Alden Manipula, EIT

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