A symmetrical framework consisting of threepin-connected bars is loaded by a force P (see figure).The angle between the inclined bars and the horizontalis α = 52°. The axial strain in the middle bar...

A symmetrical framework consisting of three
pin-connected bars is loaded by a force P (see figure).
The angle between the inclined bars and the horizontal
is α = 52°. The axial strain in the middle bar is
measured as 0.036.
Determine the tensile stress in the outer bars if
they are constructed of a copper alloy having the following
stress-strain relationship:
σ = 18,000ε/(1 + 300ε)        0 ≤ ε ≤ 0.03 (σ=  ksi)