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RE: Void Forms under Grade Beams

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Grade beams on void boxes - No Uplift unless tied to floor.
Uplift on piers - yes through skin friction, need to account for this in the design and steel in pier.  Geotech should give you active zone (depth) and uplift force per unit area.
Note:  If you bell the piers then the tensile stresses are likely to control the steel percentage.
-----Original Message-----
From: Gerard Madden, SE [mailto:gmadden(--nospam--at)]
Sent: Tuesday, May 24, 2005 1:34 PM
To: seaint(--nospam--at)
Subject: Void Forms under Grade Beams

I have a soils engineer requiring me to design grade beams for a pier and grade beam residential foundation for an uplift of 1500 psf. He is also requiring void forms underneath the grade beams…. I thought this was an either or type of thing, not both. It’s a 1 story house and this will easily govern the design.


Any input appreciated.