Question

ing stress. Problem 5.4.B. A sin a span of 18 ft (5.40 placed at the third SAR A simple beam of Douglas fir-larch, select structural grade, has 18+ 15.49 m) with two concentrated loads of 4 kips (13.34 kN) each at the third points of the span. Neglecting its own weight, determine the the beam with the least cross-sectional area based on bending stress.

Answer 1

given for a Floor beam given with two point loads of 4000lb at third points and a length of 18 ft, and made of select structural Douglas Fir-larch The Monimum applied moment. M = PL = 4000 x 18 3 = 24,000 lb ft = 288,000 lb in M in the Next determine The Minimum size member. Note that from The table book, The Man bending stress is 1600 psi, assuming that there are no significant factors reduction factors. section Modulus: Assume 3.5 for b. s = 12 bh2 = 1/2 (3-5) 62 = 0.583h2 substitue 2,8,8,000 lb in formy 1600 psi foro 1600 = 288000 0.58312 th=1706 use the most common size that is targer than 3.5in by tin use a 4x18