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RE: Rebar Spacers in PC beams

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Doesn't answer your questions, but that a lot of steel for such a small
beam... is it Overreinforced? Is it ductile?

-gm

-----Original Message-----
From: Glen Underwood [mailto:gunderwood(--nospam--at)clarkpac.com] 
Sent: Thursday, January 27, 2005 2:32 PM
To: seaint(--nospam--at)seaint.org
Subject: Rebar Spacers in PC beams

I've designed a conventionally reinforced precast beam with two layers of 
longitudinal tension reinforcement - specifically - 8 - #7's in two layers 
of 4 each.  The design clear spacing between the two layers is 1".  The 
beam is 12" x 13" and will be a composite tee-beam when the slab is cast on 
top.

The production crew has achieved the 1" clear spacing by placing a short 
stub of #8 bar between the two layers of longitudinal steel.  This happens 
every 5 feet or so along the beam length.

Knowing that the concrete will crack (and crack control requirements are 
met), is there any problem with this method?  I have never seen this done 
before in the tension zone of a beam.  My experience has been that 
longitudinal bar elevs are set by tie wire hangers, and it looks odd to me 
to introduce a weakened plane in the tension zone of a beam.  Would the 
solid bar/weakened plane cause normal flexural cracks to propagate further 
up the depth of the beam?

Thanks in advance.

Sincerely,

Glen A. Underwood, SE
Clark Pacific


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