Civil Engineering Reference
In-Depth Information
10.12 Why are the actual dimensions of lumber different from the nominal
dimensions? Explain.
10.13 What are the factors considered in grading lumber? What are the
main grades of hardwoods and softwoods?
10.14 State five different imperfections that may be found in lumber, and
briefly define them.
10.15 Sketch the typical stress-strain curve for wood. On the graph, show
the modulus of elasticity.
10.16 Compute the modulus of elasticity of the wood species whose
stress-strain relation is shown in Figure 10.9, using both the SI and
English units. Compare the results with the typical values shown in
Table 1.1 and comment about the results.
10.17 List five different tests used to evaluate the mechanical properties of
wood.
10.18 A wood specimen was subjected to bending until failure by applying
a load in the middle of its span. The specimen has a cross section of
and a span of 14 in. The load and the deflection in the
middle of the span were recorded as shown in Table P10.18.
a. Using a computer spreadsheet program, plot the load-deflection
relationship.
b. Plot the proportional limit on the graph.
c. Calculate the modulus of rupture (flexure strength).
1 in.
*
1 in.
Table P10.18
Load (lb)
Deflection (in.)
0
0
8
0.149
16
0.227
28
0.295
60
0.365
111
0.404
156
0.437
198
0.468
243
0.502
286
0.537
328
0.581
365
0.616
10.19. A wood specimen having a square cross section of
2 in.
*
2 in.
was
tested in bending by applying a load at the middle of the span,
where the span was 28 in. The deflection under the load was mea-
sured at different load levels as shown in Table P10.19.
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