F-18. A traffic light and signal pole is subjected to the weight of each traffic signal W, 45 lb and the weight of the road lamp W, 55lb.Thepole is fixed at the base. Find the principal normal stresses and the maximum shear stress on element B located 19 ft above the base (see figure). Assume that the weight of the pole and lateral arms is included in the signal and lamp weights. [Ans.max=2689 psi] 55 lb 15 ft 45 lb 45 lb 45 lb 45 lb 15 ft 45 lb B 13 ft 10 ft 15 ft 10 ft 15 ft- =0.2 in.- B d = 14 in. 17 ft