oto by U. S. Forest
Service_]

The lateral bending of a column produces a combination of
bending with compressive stress over the section, the
compressive stress being maximum at the section of greatest
deflection on the concave side. The convex surface is under
tension, as in an ordinary beam test. (See Fig. 6.) If the same
stick is braced in such a way that flexure is prevented, its
supporting strength is increased enormously, since the
compressive stress acts uniformly over the section, and failure
is by crushing or splitting, as in small blocks. In all columns
free to bend in any direction the deflection will be seen in the
direction in which the column is least stiff. This sidewise
bending can be overcome by making pillars and columns thicker in
the middle than at the ends, and by bracing studding, props, and
compression members of trusses. The strength of a column also
depends to a considerable extent upon whether the ends are free
to turn or are fixed.

[Illustration: FIG. 6.--Unequal distribution of stress in a long
column due to lateral bending.]

|-------------------------------------------------------|
| TABLE IV |
|-------------------------------------------------------|
| RESULTS OF COMPRESSION TESTS ACROSS THE GRAIN ON |
| 51 WOODS IN GREEN CONDITION, AND COMPARISON WITH |
| WHITE OAK |
| (U. S. Forest Service) |
|-------------------------------------------------------|
| | Fibre stress | Fiber stress |
| COMMON NAME | at elastic | in per cent |
| OF SPECIES | limit | of white oak, |
| | perpendicular | or 853 pounds |
| | to grain | per sq. in. |
|-----------------------+---------------+---------------|
| | Lbs. per | |
| | sq. inch | Per cent |
| | | |
| Osage orange | 2,260 | 265.0 |
| Honey locust | 1,684 | 197.5 |
| Black locust | 1,426 | 167.2 |
| Post oak | 1,148 | 134.6 |
| Pignut hickory | 1,142 | 133.9 |
| Water hickory | 1,088 | 127.5 |
| Shagbark hickory | 1,070 |