The weight of the framed truss will be in proportion to the load and to the span. This, for the weight upon a foot horizontal, will about equal -

T = 0.077 Cs;

which equals the weight in pounds per foot horizontal to be allowed for a wooden truss with iron suspension-rods and a horizontal tie-beam, near enough for the requirements of our present purpose; where s equals the length or span of the truss, and C the weight per foot horizontal of the roof covering, as in equation (92.). Substituting for C its value, as in (92.), we have -

T = 0.0077 s 2 1p/s;

or -

T= 0.0154 lp; (93.)

which equals the weight in pounds per foot horizontal to be allowed for the truss.

Effect Of Wind On Roofs