Four wood boards 1 in. by 6 in. in cross section are stacked as shown and used as an 8-ft-...

Four wood boards 1 in. by 6 in. in cross section are stacked as shown and used as an 8-ft-long simply supported beam. A 400-lb concentrated load is applied at the center of the span. Neglecting the weight of the beam, calculate the following based on the full nominal (rough) dimensions:

Problem

(a) the maximum bending stress (boards not glued together)

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(b) the maximum bending stress if the boards are glued together

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(c) the maximum shear stress in the middle glued joint