14 kip B - 4.5 ft- -4.5 ft - 3 ft -|

A beam is subjected to equal 21.7 kip-ft bending moments. Assume t₁ =t₂ = tw- 3 in., d = 15 in., b₁ = 6 in., and b₂ =8 in. The cross- sectional dimensions of the beam are illustrated. Determine: (a) the distance y to the centroid (measured from the bottom), the moment of inertial₂ about the z axis, and the controlling section modulus S₂ about the z axis. (b) the bending stress at point H (positive if tension, negative if compression). (c) the bending stress ok at point K(positive if tension, negative if compression). (d) the maximum bending stress max produced in the cross section (positive if tension, negative if compression). M Answers: (a) y = (b) 6μ = 6.978 (c) OK (c) omax = = i M in., I₂ = X i psi. psi. psi. 41 1₂ 2886.59 b₁ b₂ Cross section H K in.4, S₂ = i in.³.

The shaft is supported by smooth journal bearings at A and B that only exert vertical reactions on the shaft. Determine its smallest diameter d if the allowable bending stress is sallow = 180 MPa.