One-tenth of this must be taken as a safe working load = 288 lbs.
The strength of cylindrical posts is to square ones as 10 is to 17, the rest of the formula remaining the same, except that d = diameter of post in inches.
When the pillar is rectangular.—Multiply the greater side by the cube of the lesser in inches, and divide by the square of the length in feet. The quotient multiplied by the value of D (Table II.) will give the weight which the post will carry in pounds.
The formula is as follows:
W = (BT3 × D)/L2,
where B = breadth of post in inches;
T = least thickness in inches, and the rest of notation as before.
Example.—Find the weight that may be placed on a rectangular post of Dantzic oak 8 in. by 6 in. and 18 feet long.
The value of D (Table II.) being 2,410 lbs.,