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RE: Modeling Spread Footings for buildings

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Designing the spread footing for the gravity loads and using grade beams
(normally at an elevation above the spread footing) to resist the base
moments is the cleanest way of resolving this issue IMHO. If you try to use
the spread footing for both then a more elaborate design using beam on
elastic foundation analysis is needed. In California, mostly the practice is
to de-couple the moment and gravity at foundation level.

Ben Yousefi, SE
San Jose, CA

	-----Original Message-----
	From:	Alex C. Nacionales [SMTP:acnacionales(--nospam--at)yahoo.com]
	Sent:	Sunday, February 03, 2002 11:04 PM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Modeling  Spread Footings for buildings

	I have always modeled spread footings as a fixed support at the
level of the natural ground line then designed the footing for the axial
load and moment from the columns. Lately I found from a textbook (Seismic
Design of RC and Masonry Buildings by Paulay and Priestly), where it says it
is better to model it as a hinged support and put Footing Tie Beams to take
care of the moments. It also states that the location where the base shear
acts, Whether at the base of the footing or at the natural ground line must
be established. I have always assumed it to be acting at the natural ground
level.
	
	Your comments and opinions will be appreciated. TIA.
	
	Alex C. Nacionales
	
	
	

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