Building Design and Construction Handbook - Merritt - Ventech!

10.16 SECTION TEN
10.5.7 Flat-Use Factor
TABLE 10.9 Loading Condition Coefficient K L for Glulam
Beams
Single-span beams
Loading condition K L
Concentrated load at midspan 1.09
Uniformly distributed load 1.0
Two equal concentrated loads at third points of span
Continuous beams of cantilevers
0.96
All loading conditions 1.0
Design values for sawn lumber beams adjusted by the size factor C fu assume that
load will be applied to the narrow face. When load is applied to the wide face
(flatwise) of dimension lumber, design values should be multiplied by the appropriate
flat-use factor given in Table 10.10. These factors are based on the sizeadjustment
equation in ASTM D245. Available test results indicate that this equation
yields conservative values of C fu.
When a glulam member is loaded parallel to the wide face of the laminations
and the member dimension parallel to the face is less than 12 in, the design value
for bending for such loading should be multiplied by the appropriate flat-use factor
in Table 10.11.
10.5.8 Repetitive Member Factor
Design values for bending F b may be increased when three or more members are
connected so that they act as a unit. The members may be in contact or spaced up
to 24 in c to c if joined by transverse load-distributing elements that ensure action
of the assembly as a unit. The members may be any piece of dimension lumber
subjected to bending, including studs, rafters, truss chords, joists, and decking.
When the criteria are satisfied, the design value for bending of dimension lumber
2 to 4 in thick may be multiplied by the repetitive member factor C r � 1.15.
TABLE 10.10 Flat-Use Factors C fu for
Dimension Lumber
Width, in
Thickness, in
2 and 3 4
2 and 3 1.0
4 1.1 1.0
5 1.1 1.05
6 1.15 1.05
8 1.15 1.05
10 and wider 1.2 1.1
TABLE 10.11 Flat-Use Factors C fu for
Glulam Beams
Lamination
width, in C fu
10 3 ⁄4 or 10 1 ⁄2 1.01
8 3 ⁄4 or 8 1 ⁄2 1.04
6 3 ⁄4 1.07
5 1 ⁄8 or 5 1.10
3 1 ⁄8 or 3 1.16
2 1 ⁄2 1.19