The three beams shown have approximately the same cross-sectional area. Beam 1 is a W 14 x 82 with flange plates; Beam 2 consists of a web plate with four angles; and Beam 3 is constructed of 2 C shapes with flange plates.
(a) Which design has the largest moment capacity?
(b) Which has the largest shear capacity?
(c) Which is the most economical in bending?
(d) Which is the most economical in shear?
Assume allowable stress values are: σa = 18 ksi and τa = 11 ksi. The most economical beam is that having the largest capacity to-weight ratio. Neglect fabrication costs in answering (c) and (d) above.

8 x 0.52 4 x 0.375 Four angles 15 50 14 x 0.675 W 14 x 82 -4 0.375 8 x 0.52 Beam 2 Beam1 Beam 3