SIZES AND WEIGHTS OF SEPARATORS FOR CARNEGIE
STEEL BEAMS.

Separators for 20" beams are made of metal.
Separators for 6" to 15" beams are made of '' metal.
Separators for 5'' beams and under are made of " metal.

SIZES AND WEIGHTS OF SEPARATORS FOR CARNEGIE
IRON BEAMS.

Separators for 6" beams and upward are made of " metal.
Separators for 5'' beams and under are made of §' metal.

CHAPTER XV.

STRENGTH OF CAST-IRON. WOODEN, AND STONE BEAMS -SOLID BUILT BEAMS.

Cast-Iron Beams.

Most of our knowledge of the strength of cast-iron beams is derived from the experiments of Mr. Eaton Hodgkinson. From these experiments he found that the form of cross-section of a beam which will resist

the greatest transverse strain is that shown in Fig. 1, in which the bottom flange contains six times as much metal as the top flange.

When cast-iron beams are subjected to very light strains, the areas of the two flanges ought to be nearly equal. As in practice it is usual to submit beams to strains less than the ultimate load, and yet beyond a slight strain, it is found, that when the flanges are as 1 to 4, we have a proportion which approximates very nearly the requirements of practice. The thickness of the three parts - web, top flange, and bottom flange — may with advantage be made in proportion as 5, 6, and 8.

Fig. 1.

If made in this proportion, the width of the top flange will be equal to one-third of that of the bottom flange. As the result of his experiments, Mr. Hodgkinson gives the following rule for the breaking-weight at the centre for a cast-iron beam of the above form:

Breaking-load in tons =

Area of bot. flange depth
X
× 2.426
in square inches in ins.

clear span in feet

(1)

Cast-iron beams should always be tested by a load equal to that which they are designed to carry.

Wooden Beams. - Wooden beams are almost invariably square or rectangular shaped timbers, and we shall therefore consider only that shape in the following rules and formulas.

For beams with a rectangular cross-section, we can simplify our formulas for strength by substituting for the moment of inertia 1 × 3 where breadth of beam, and d its depth.

its value, viz.,

12

Then, substituting this value in the general formulas for beams, we have for rectangular beams of any material the following formulas:

Beams fixed at one end, and loaded at the other (Fig. 2).

Beams fixed at one end, and loaded with uniformly distributed load (Fig. 3).