Georgia-Pacific Engineered Lumber Canada - Manual (Page 6)

6
GeorGia-Pacific Wood Products
JaN 2014
caNadiaN iNstallatioN iNstructioNs
Pa
Ge
web stiffener requirements
A web stiffener is a wood block that is used
to reinforce the web of an I-Joist at
locations where:
• The webs of the I-Joists are in jeopardy
of buckling out of plane. This usually
occurs in deeper I-Joists.
• The webs of the I-Joist are in jeopardy of
“knifing” through the I-Joist flanges. This
can occur at any I-Joist depth when the
design reaction loads exceed a specific level.
• The I-Joist is supported in a hanger and
the sides of the hanger do not extend up
to the top flange. With the top flange
unsupported by the hanger sides, the
joist may deflect laterally, putting a twist
in the flange of the joist. The web stiffener
supports the I-Joist along a vertical axis as
designed. (In this application, the web
stiffener acts very much like a backer block.)
There are two kinds of web stiffeners:
bearing stiffeners and load stiffeners. They are
differentiated by the applied load and location
of the gap between the slightly undersized
stiffener and the top or bottom flange.
Bearing stiffeners are located at the reactions,
both interior and exterior, when required.
I-Joists do not need bearing stiffeners at any
support when subjected to normal residential
form loads and installed in accordance with
the allowable spans.
Load stiffeners are located between supports
where significant point loads are applied to the
top flange of an I-Joist.
Web stiffener blocks may be comprised of
lumber, rim board, or structural wood
panels. The minimum grade of structural
wood panels is Rated Sheathing; minimum
lumber grade is Utility grade SPF (south) or
or better. Any rim board product would also
work satisfactorily.
web stiffener should be equal to the distance
Ideally, the depth of the
between the flanges of the joist minus
1 ⁄
8
inch-¼ inch. For bearing stiffeners, this gap
is placed between the stiffener and the bottom
of the top flange. For load stiffeners, the gap
is located at the bottom of the stiffener.
Gap
Tight Joint
No Ga p
Concentrated Load
(Load stiffener )
End Bearing
(Bearing stiffener)
±2"
±2"
"- "
Gap
Tight Joint
No Ga p
Gap
No Gap
Use minimum of
four 8d nails
Flange width
2½" or 3½"
Designation Web Stiffener Size Each Side of Web
WI 40, WI 60 1" x 2 " min. width
WI 80 1½" x 2 5 ⁄
16
5 ⁄
16
" min. width
1. A bearing stiffener is required in all
engineered applications which exceed the
"no stiffeners" factored reaction resistances
indicated in the product guide. The gap between
the stiffener and the flange is at the top.
2. A load stiffener is required at locations where
a concentrated load greater than 1500 pounds
unfactored load is applied to the top flange
between supports, or in the case of a
cantilever, anywhere between the cantilever tip
and the support. The gap between the stiffener
and the flange is at the bottom.
3. A bearing stiffener is required when the
I-Joist is supported in a hanger and the sides
of the hanger do not extend up to, and support,
the top flange. The gap between the stiffener
and flange is at top.
10d nails required
for I-Joists with 3½"
flange width (WI 80)
1 ⁄
8 1 ⁄
4
web stiffener requirements
web stiffener size requirement