5.65 and 5.66 For the beam and loading shown, design the cross section of the beam, knowing that the grade of timber used has an allow- able normal stress of 12 MPa. 1.8 kN 3.6 kN 40 mm D. 0.8 m 0.8 m 0.8 m B.

5.16 The box beam is made by nailing four 2-in. by 8-in. planks together as shown. (a) Show that the moment of inertia of the cross-sectional area about the neutral axis is 981.3 in.. (b) Given that wo 300 lb/ft, find the largest allowable force P if the bending stress is limited to 1400 psi. 8 in.2 in. 8 in. 9 f 3 ft 2 in. FIG. P5.16

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5.5 in. Design the height h of the cross section to support the loading 1.1 kip/ft shown. For the timber used, the allowable normal stress is 1800 psi and the allowable shear stress is 300 psi. A B 4 ft 4 ft

For the beam and loading shown, determine the minimum required width b, knowing that for the grade of timber used, Gall = 18 MPa and Tall = 975 kPa. b = 43 mm 2.0 kN 6.8 kN 8.4 kN B D 300 mm 4 m 4 m 4 m 0.50 m

PROBLEM 4.The beam AB consisting of a cast iron plate of uniform thickness, b, and length, L, is to support the distributed load w(x) shown a) Knowing that the beam is to be of constant strength (fully stressed beam), express h in terms of x, L and ho. b) Determine the smallest value of ho if L=800 mm, b=25 mm, wo=300 kN/m and oall=200 MPa. w-=WoCos(ITX/2L) A ho B

2. For the beam and loading shown, determine the minimum required width b, knowing that for grade of timber used, aall = 12MPA and Tal = 825k Pa. 8,2 kN 4.4 kN 3.6 kN B D 0.25 m 1 m 2.5 m 0.5 m 2 m