STRINGERS.

From Plate III find the equivalent live load per lineal foot for a span equal to the panel length, add to same the assumed weight per foot of two stringers and the floor they support, and divide the sum by two, calling the result w ; then find the total bending moment at mid-span by substituting in the well-known formula,

where l is the panel length in feet, and M is the required moment in foot-pounds.

Should the total end shear be required, it can be found for each stringer by adding together the end shear given on Pl. II and the total weight of one stringer with the floor that it carries, and dividing the sum by two.

FLOOR-BEAMS.

In proportioning a floor-beam, the important thing to ascertain is the total concentration at the point where two stringers meet. The live-load concentration is to be found by multiplying together the panel length and the equivalent uniform load per lineal foot given on Pl. III for a span equal to twice the panel length, and dividing the product by two. It is unnecessary to describe here how the dead-load concentration at each stringer support is to be found. Nor is it necessary to do more than merely mention that the live-load concentration obtained for the floor-beam is the same as that required in finding stresses in primary-truss members.

TRUSSES.

These can be divided into two kinds, viz., those with equal panels and parallel chords, and those in which the panel lengths are unequal, or the chords are not parallel, or both. In the first case, the stresses can be determined most expeditiously by substitution in tabulated formulae, and in the second case by the graphical method.