for the area of the lower flange.
Example.—Required the dimensions of a cast-iron beam, of Mr. Hodgekinson’s form, for a span of thirty feet, to support a load of ten tons at the centre.
| Span | 30 feet, | Whence— | |
| Length | 34 feet, | Length | 34 feet, |
| Load | 10 tons at centre. | Span | 30 feet, |
| Depth | 25½ inches, | ||
| Lower flange | 32.58 square inches, | ||
| Upper flange | 5.34 square inches, |
a = 6 × 10 × 12 × 30
26 × 34 × 12
16 = 32.58
and 32.58
6.1 = 5.34.
and the area of the top flange will be
36
6 = 6,
whence the following dimensions:—
| Length | 30 | feet, |
| Depth | 23 | inches, |
| Lower flange | 36 | square inches, |
| Upper flange | 6 | square inches, |