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BEARING STRENGTH OE WOOD
AT ANGEE TO THE GRAIN
No. 12€3
Revised March 1956
FOREST PRODUCTS LABORATORY
MADISON S.WISCONSIN
n UNIV. OF FL LIB
DOCUMENTS DEPT.
U.S. DEPOSITORY
HUME LIBRARY
OCT ul )272
'i^S- Univ. of Florida'
UNITED STATES DEPARTMENT OF AGRICULTURE
FOREST SERVICE
In Cooperation with the University of Wisconsin
BEAEING STRENGTH OF WOOD AT ANGLE TO THE GRAIN!
By
)rat
U. S. Department of Agriculture
Forest Products Laboratory,— Forest Service
The compressive strength of wood depends on the direction of the grain
with respect to the direction of the applied force. It is highest
parallel to the grain and lowest perpendicular to the grain, and for
other angles has intermediate values. The ratio between the values
perpendicular and parallel to the grain are not the same for different
species of wood and also vary with the method of applying the load. For
example, the basic stress of Douglas-fir is 1,^50 pounds per square inch
parallel to the grain and 235 pounds perpendicular to the grain, while
for oak these respective values are 1,350 and 365. The safe load on a
1-inch bolt in a 6-inch Douglas-fir timber is 5 ,8^0 pounds parallel to
the grain and 2,^40 pounds perpendicular to the grain.
On account of this variation in the magnitude and relationship of the
compressive strength parallel and perpendicular to the grain, the
determination of the proper value for intervening angles has always been
a difficult problem in timber design. To present values in tables for
all the conditions would be impracticable. The bearing values for inter-
vening angles, therefore, are usually obtained from the values parallel
and perpendicular to the grain by the use of the Hankinson formula. This,
however, involves a separate calculation for each individual condition
and in order to provide a more convenient method the accompanying nomo-
graph, based on the formula, has been developed by John A. Scholten of
the U. S. Forest Products Laboratory.
The nomograph is based on the Hankinson formula, which is considered
most applicable by the U. S. Forest Products Laboratory.
By means of this nomograph the stress or load for any intervening angle
can be obtained from the stress or load parallel and perpendicular to the
grain without any calculation. The symbols in the chart are represented
^Original report by J. A. Newlin, Specialist in the Mechanics of Wood,
published in Engineering News-Record May 11, 1939*
^Maintained at Madison, Wis., in cooperation with the University of
Wisconsin.
Eept. No. 1203 -1- Agriculture-Madison
by allowable loads or stresses, but the formula is applicable for loads
or stresses generally. The intercepts on any vertical line are pro-
portional to sin20 from to 90 degrees. The scale of the chart was
chosen primarily for convenient use with bolt loads, but for greater
or lesser values or for different units, the magnitude of the scale can
be adjusted to obtain greater accuracy without affecting the chart 'b
applicability.
Rept. No. 1203 -2- 1.-1+
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