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RE: PS CONCRETE: Torsion in Double-Tees

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First, is the double tee also connected at the flanges to adjacent tees?
If so, it seems that it would share load with other tee webs as well,
reducing the torsional effect. 

If you do evaluate the load as torsion on one double tee, you can view
it as a load centered between the webs, plus a torsional moment that is
resisted by a vertical load couple at the webs (i.e., similar to warping
torsion in a steel beam in lieu of St. Venant torsion). 
 

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

________________________________

	From: Polhemus, Bill [mailto:bill.polhemus(--nospam--at)tyson.com] 
	Sent: Wednesday, May 25, 2005 9:37 AM
	To: seaint(--nospam--at)seaint.org
	Subject: PS CONCRETE: Torsion in Double-Tees

	I'm analyzing a 10DT32 (precast prestressed double-tee that is
ten feet in width and 32 inches deep) roof beam. There is load on it
from an equipment platform resting directly atop one of the stems.

	"Theoretically" this can be viewed as an eccentrically-placed
load with respect to the double-tee centroid. However, analyzing it in
this way puts a torque into the beam that is unacceptably high.

	But I can't help but view this as a loaded SINGLE-TEE beam half
the width of the double tee, with the only needed check being the
flexure induced in the continuous flange between the stems.

	Any thoughts? 

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