Length, 16
Height, 1
Area Top Flange, 1.0
Area Bottom Flange, 6.1
In the above formula for cast iron beams,
W = weight in tons.
a = area in square inches of bottom flange.
d = depth in inches.
h = length in inches.
The web uniting the two flanges must be made solid—as any opening, by causing irregularity in cooling, would seriously affect the strength of the beam.
Example.—Required the dimensions of a Hodgkinson girder—for a span of 60 feet—with a load of 10 tons in the centre.
= 37 inches nearly.
and the area of the top flange will be,
37 ÷ 6 = 6.16 inches—
so that our dimensions will be as follows:
Length, 30 feet.
Depth, 45 inches.
Area Top Flange, 6.16 inches.
Area Bottom Flange, 37 inches.
