CIVIL ENGINEERING FORMULAS

TIMBER ENGINEERING FORMULAS 175

(6.60)

(6.61)

The ultimate unit load is:

(6.62)

For lumber of various types, the following formulas can be used, where
Sallowable compressive stress; and dleast dimension of the lumber
cross section.

(6.63)

(6.64)

(6.65)

(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/AtoQ/Afor solid column of same dimensions depends on L/d
and is as follows:

 61014182226

Ratio0.82 0.77 0.71 0.65 0.74 0.82 (6.67)

L

d

Q

A

 (^1200)  1 0.00000112

L

d



4

,K23.35

Douglas fir

S 1250

E1,600,000

Q

A

 (^1100)  1 0.00000168

L

d



4

,K21.10

Southern cypress

S 1100

E1,200,000

Q

A

 (^1450)  1 0.00000162

L

d



4

,K21.23

Longleaf yellow pine

S 1450

E1,600,000

Q

A

 (^700)  1 0.00000097

L

d



4

,K24.2

Hemlock

S 700

E1,100,000

P

A

 4

Q

A

Q

A

S up to

L

d

 11

Q

A



0.274E



L

d

2 for

L

d

K