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- Sample of Floor
Beam Investigation
Floor beam bracing
The braces located in the center portion
of each beam (tension flange brace), and
those
located at and near columns (compression
flange brace), are treated differently in
design.
1) Braces in center portion: The only
requirement I am aware of is the Sidesway
web
buckling provisions of AISC 9th, K1.5.
The Mfg. rdawings (partial set) we have,
do not indicate beam section geometry, or
WF size, so the following shows K1-5
calculations
for beams roughly similar in size.
K1-5 is for point loaded beams, and it
excludes uniformly loaded beams from the
check altogether. Since our case is
somewhat in-between, (joist point loads
at 2' o.c.)
I used the load from 2 joists
arbitrarily.
The midspan braces can be removed, but it
is necessary to install stiffeners per
K1-5,
unless more detailed review is
undertaken. (K1-5 is based on research by
Yura (1982),
which could be studied further.
2) Braces at and near columns: These
braces are critical, as they determine
the unbraced
length utilized in the original design
for allowable bending stress. At 2' o.c.
the beam
Fb was likely 0.6Fy. If unbraced length
increases to the length between
inflection points,
due to brace removal, the allowable
bending stress likely goes down
significantly.
A suggested work around is to install
stiffeners, and run brace from joist top
chord to a
point in the lower third of the
stiffener.

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General Information:
Thomas R. Price,
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