The factor safety is 1⁄8. Therefore the safe load will be 16,970 lbs.
The strength of cylindrical pillars is to square ones as 10 is to 17.
Braces and Ties subject to a Tensional Strain.—The weight that will produce fracture in a beam strained in the direction of its length, is in proportion to the area of the cross section of the beam multiplied by the weight that would fracture a unit of that area.
The formula is as follows:
B.W. = E S
where E = the cohesive force in lbs. per unit of 1 square inch, as in Table III.
S = the sectional area of the beam in square inches.
Example.—Find the B.W. of a rectangular elm brace 9 in. by 3 in. under a tensional strain.
The value of E (Table III.) is 4,480.
B.W. = 4,480 × 9 × 3 = 120,960 lbs.
One-fifth of this should be taken as a safe load,