The structure shown in the figure consists of a horizontal rigid bar ABCD supported by two steel wires, one of length L and the other of length 3L/4. Both wires have cross-sectional area A and are made of elastoplastic material with yield stress σY and modulus of elasticity E. A vertical load P acts at end D of the bar.
(a) Determine the yield load PY and the corresponding yield displacement δY at point D.
(b) Determine the plastic load PP and the corresponding displacement δP at point D when the load just reaches the value PP.
(c) Draw a load-displacement diagram with the load P as ordinate and the displacement δD of point D as abscissa.