Prob. 3.7-12. A "rigid" beam AD is supported by a smooth

pin B and by vertical rods that are attached to the beam at

points A and C, as shown in Fig. P3.7-12. Neglect the weight

of the beam. The beam is horizontal when only rod (1) is at-

tached and P = 0, but rod (2) was manufactured 5 = 0.5 mm

too short. Determine the axial stresses , and ₂ induced in

the respective support rods after rod (2) is attached to the

upper bracket and the load P = 20 kN is applied. Assume

that is small.

A₁ = A₂ = 200 mm², L₁= L₂ = 2m

E₁70 GPa, E₂= 100 GPa

P = 20 kN, a = 1 m. b = 1.5m

(1)

(2)

C

8=0.5 mm

"Rigid"

P3.7-12, P3.8-21, and P3.9-15

D