The truss shown in Figure P5.15-6 is part of a roof system supporting a total gravity load of 40 psf of roof surface, half dead load and half snow. Trusses are spaced at 10 feet on centers. Assume that wind load is not a factor and investigate the adequacy of a W6 × 12 of A992 steel for use as a purlin. No sag rods are used, so lateral support is at the ends only.
a. Use LRFD.
b. Use ASD.