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Re: Precast Panel Cracking

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	Chad,
		The only thing I can suggest is that the horizontal crack
may not be only at a reveal but also at a strand location. A longitudinal
split in a prestressed wall panel can occur if the prestressing is not
uniformly spaced (more or less) across the section, or if the strand is too
close to the face and no other reinforcing exists to stop any crack that
starts. Is there any mesh or other reinforcing in either wythe, or just
prestressing?
		The only reason I can imagine for the crack at 2' from the
each end of every panel is nonuniform grouting (or other bearing) in the
joints. 2' is near the transfer length for the prestress force, so there
should be good prestress there, much more than any creep or shrinkage should
overcome. Most of precast's creep and shrinkage has occurred by the time it
is erected, and a building maybe three times as long can be built without an
expansion joint (with lots of reasons to make it shorter or longer). Still,
extremely cold weather could have contributed.
		Similarly, the welds all cracking is unusual. Usually, after
one (or one line) fails, that location continues to move and the other welds
hold.
		Wall panels sitting horizontally, taking vertical loads and
kept from folding up by columns and perpendicular walls are not unusual,
though are not the most common configuration.
	Jim Getaz
	Precast Engineer
	V: 540-665-3204
	F: 540-665-3250


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