Page 241 - Civil Engineering Formulas
P. 241
TIMBER ENGINEERING FORMULAS 175
Q 0.274E L
for K (6.60)
L
A 2 d
Q d L
S up to 11 (6.61)
A d
The ultimate unit load is:
P Q
4 (6.62)
A A
For lumber of various types, the following formulas can be used, where
S allowable compressive stress; and d least dimension of the lumber
cross section.
Hemlock
Q L 4
S 700 700 1 0.00000097 , K 24.2
A d
E 1,100,000
(6.63)
Longleaf yellow pine
Q L 4
S 1450 1450 1 0.00000162 , K 21.23
A d
E 1,600,000
(6.64)
Southern cypress
Q L 4
S 1100 1100 1 0.00000168 , K 21.10
A d
E 1,200,000
(6.65)
Douglas fir 4
Q L
S 1250 1200 1 0.00000112 , K 23.35
A d
E 1,600,000
(6.66)
For general structural use under continuously dry conditions for laminated
wood with cover plates or boxed around a solid core, square or rectangular with
ends flat:
Ratio of Q/A to Q/A for solid column of same dimensions depends on L/d
and is as follows:
L
61014182226
d
Ratio 0.82 0.77 0.71 0.65 0.74 0.82 (6.67)
