Question 6 (20 marks) The structure shown in Figure Q6 consists of a horizontal rigid bar OBCD supported by two steel wires: one of length L and the other of length 34/4. Both wires have cross- sectional area A and are made of elastoplastic material with yield stress oy and modulus of elasticity E. A vertical load P acts at the end of the bar D. (a) Determine the yield load PY and the corresponding yield displacement oy at point D. (12 marks) (b) Determine the plastic load Pp and the corresponding displacement oy at point D when the load just reaches the value Pp. (4 marks) (c) Draw a load-displacement diagram with the load P as vertical axis and the displacement on of point D as horizontal axis. (4 marks) 3/AL O B C D P 2b b -b- Figure Q6