고체역학 (Beer) — Analysis and Design of Beams for Bending: Problem 5.91

5.91 Each of the three rolled-steel beams shown (numbered 1, 2, and 3) is to carry a 64-kip load uniformly distributed over the beam. Each of these beams has a 12-ft span and is to be supported by the two 24-ft rolled-steel girders AC and BD. Knowing that the allowable normal stress for the steel used is 24 ksi, select (a) the most eco-nomical S shape for the three beams, (b) the most economical W shape for the two girders.