In Table XXI are given the safe loads which may be placed on beams of long-leaf yellow pine, of various depths, on various spans.

*From Handbook of the Cambria Steel Company.

Table XXII. * Strength Of Solid Wooden Columns Of Different Kinds Of Timber

DoUGLAS,

Oregon and

Washington

Yellow Fir or Pine

Southern, Long-Leaf or Georgia Yellow Pine, Canadian (Ottawa) White Pine, (Ontario) Red Pine

White Oak

Northern or Short-Leaf Yellow Pine, Red Pine, Norway Pine, Spruce, Eastern Fir, Hemlock

White Pine

F

G,000

5,000

4,500

4,000

3,500

I d

4

5,876

4,897

4,407

3,918

3,428

6

5,739

4,782

4,304

3,826

3,347

8

5,566

4,638

4,174

3,710

3,247

10

5,368

4,474

4,026

3,579

3,132

12

5,156

4,297

3,867

3,438

3,008

14

4,937

4,114

3,703

3,291

2,880

16

4,716

3,930

3,537

3,144

2,751

18

4,498

3,748

3,373

2,998

2,624

20

4,286

3,571

3,214

2,857

2,500

22

4,082

3,402

3,061

2,721

2,381

20

3,703

3,0S6

2,777

2,469

2,160

30

3,366

2,805

2,524

2,244

1,963

36

2,934

2,445

2,200

1,956

1,711

40

2,690

2,241

2,017

1,793

1,569

50

2,203

1,835

1,652

1,468

1,285

To find the load that a wooden column will support per square inch of sectional area, from the above table, the length of the column in inches is divided by the least diameter of the column, and the result is the ratio of length to diameter of the column. From this ratio is found the ultimate strength per square inch of section of a column of any kind of wood given in the table. A factor of safety of 5 should be used in finding the size of column required; that is, the working load should not be greater than one-fifth of the values given in the table.

The values given in Table XXI are the safe loads in pounds uniformly distributed, exclusive of the weight of the beam itself, for rectangular beams one inch thick. The safe load for a beam of any thickness may be found by multiplying the values given in the tables by the thickness of the beam in inches. From the last column, the deflection may be obtained, corresponding to the given span and safe load, by dividing the coefficient by the depth of the beam in inches, which will give approximately the deflection in inches.

365. Example

If a beam is required to support a uniformly distributed load of 4,000 pounds on a span of 10 feet, what would be the dimensions of the beam of long-leaf yellow pine, and what would be the deflection?

Solution. Following the line for beams of 10-foot span, it is found that a beam 8 inches deep and 5 inches wide (853 X 5 = 4,265)

*From Handbook of the Cambria Steel Company.

would support the load of 4,000 pounds, and the deflection would be 1.24 ÷ 8 = .16 inch. A second solution would be to use a beam 12 inches deep and 2 inches wide (1,920 X 2 = 3,840); but according to the table, this beam would not be quite strong enough, as it would only support a load of 3,840 pounds.