The square timber is used as a railroad tie. It carries two uniformly distrib- uted loads of 48 kN each. The reaction from the ground is distributed uniformly over the length of the tie. Determine the smallest allowable dimension b if the working stress in shear is 1.0 MPa. 0.5 m 0.2 m 48 KN 1.0 m 0.2 m FIG. P5.60 0.5 m 48 kN b b