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RE: Beam crack at support
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Beam crack at support
- From: "Kestner, James W." <jkestner(--nospam--at)somervilleinc.com>
- Date: Fri, 7 Feb 2003 10:28:28 -0600
sounds to me as if the cracking maybe a combination of shear and
tension (flexural and/or other). Is there any source of tension in
the system like post-tensioning or restrained shrinkage forces?
The flexural compression stress at the bottom of the beam may have
prevented the crack from propagating to that level.
sure that you know the cause before you repair it, otherwise it may re-crack.
design adequate? Was all the reinforcing properly
located? Any misplaced or missing stirrups? Is the in-place concrete
From: Jake Watson
Sent: Friday, February 07, 2003 9:06
Subject: RE: Beam crack at
like a tension crack (although diagonal tends to be explained as shear, and it
may be shear). If the beam is continuous or cast into the column, the
top of the beam will be in tension and the bottom in compression. This
would also explain why the beam is not cracked at the bottom. You should
be able to do a frame analysis and determine the moment at the column
face. Once you know that, you can estimate the tension stress in the
concrete. Its hard to tell when concrete will crack in tension, but if
your stress is above 5 square-roots of f`c or so, it is likely a tension
crack. You will need to make a judgment call.
the fix, call Master Builders or one of the other chemical companies and talk
with their technicians. They can be incredibly
I would appreciate feedback on the following
problem. I was called to inspect a reinforced concrete beam which exhibited
a crack at the support. The structure is composed of r/c columns, beams and
in situ slabs.
Within the slabs there are occasional
non-structural cracks running parallel to the main
The reported crack is hairline - less than 1mm in width, and it runs
diagonally from the face of the column at mid-depth of the beam,
to the underside of the slab. Therefore the crack is present in the upper
half of the beam cross-section. The beam is 21" by 16" in cross-section and
has a span of 20 feet. The floor loading above the beam should be well below
Could this be a structural shear crack even
though it does not start from the bottom of the beam cross-section? What
kind of repair do you suggest?