WOOD - Materials for Civil and Construction Engineers - page 415

(a) (b) (c) (d) (e)

(f) (g)

FIGURE 10.10 Test specimens of wood: (a) tension parallel to grains, (b) ten-
sion perpendicular to grains, (c) compression parallel to grains, (d) compression per-
pendicular to grains, (e) hardness perpendicular to grains, (f) hardness parallel to
grains, and (g) bending. (© Pearson Education, Inc. Used by permission.)

and tension parallel and perpendicular to the grain, and shear parallel to the
grain are commonly used.

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Static Bending Test
The static bending test is performed on either
or specimens. For
the large specimens, the loading head is placed on the center of the speci-
men and over a span of 710 mm (28 in.), and the load is applied at a rate
of 2.5 mm/min. (0.1 in./min.). For the small specimens, the loading head
is placed on the center of the specimen and over a span of 360 mm (14 in.), and
the load is applied at a rate of 1.3 mm/min. (0.05 in./min.). Load-deflection
data are recorded to or beyond the maximum load. Within the proportional
limit, readings are taken to the nearest 0.02 mm (0.001 in.). After the pro-
portional limit, deflection readings are usually measured with a dial gage,
to the limit of the gage, usually 25 mm (1 in.). Load and deflection of the
first failure, the maximum load, and points of sudden change are recorded.
The failure appearance is described as either brash or fibrous. Brash indi-
cates an abrupt failure and fibrous indicates a failure showing splinters.

10.9.1

50 * 50 * 760 mm

2 * 2 * 30 in. 25 * 25 * 410 mm 1 * 1 * 16 in.

1 2 1 2

Sample Problem 10.2

A static bending test was performed on a 50 * 50 * 760 mm wood sample according

to ASTM D143 procedure span between supports = 710 mm . If the maximum load

1 2

was 2.67 kN, calculate the modulus of rupture.