SI Metric

The procedure to solve SI metric is the same as that for customary units. Lumber dimensions are often given in centimeters or millimeters. Stress is in kilopascals (kPa or kN/m2). To convert from allowable stress in Appendix XI from psi (lb/in2) to kPa, multiply Scustomary by 6.8947, Table 24.2.

TABLE 24.2. Metric lumber sizes.

Nominal size (cm)

5.0 x 5.0 7.5 x 5.0 10.0 x 5.0 15.0 x 5.0 10.0 x 10.0 10.0 x 15.0

Actual size (cm)

4.5 x 4.5 7.0 x 4.5 9.0 x 4.5 14.0 x 4.5 9.0 x 9.0 9.0 x 14.0

Problem: What is the maximum point load that can be supported in the middle of a 10 x 15 cm, rough sawed (dimensions are the actual dimensions of the board) simple beam on edge that is 3.0 m long. The board is No. 1 yellow pine?

Solution: Allowable stress from Appendix XI is 1000 lb/in2. Convert this value to SI units kPa

kPa 2

0.00225

kN 3

10.34205 kN-m

3.048 m

Problem: Determine the maximum load that can be supported on the end of a finished 100 mm x 50 mm cantilever beam that is 4.0 m long. The beam is on edge and is No. 2 southern pine.

Solution: Converting allowable stress kN

SSI = 6.8947 —J x SCustomary kN lb = 6.8947 -- x 825 —T

lb/ir2 " in2

solving for K:

2 1m 1m2

100 cm 10,000 cm2

solving for W:

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