For the beam of Problem 11-5, calculate the outer fiber stresses at mid span for the following stages:

(a) transfer and

(b) under full service load. Assume the pre stress tendons are parabolically draped with a mid-span eccentricity of 9 in. as shown and zero eccentricity at the end supports. Neglect pre stress losses and use the gross concrete section properties. The pre stress force is still 250 kips. Use the load balancing method.

Problem 11-5

For the beam shown, calculate the outer fiber stresses at mid span and at the end supports at the following stages:

(a) transfer (pre stress + beam weight) and

(b) under full service load. The beam is simply supported with a span length of 20 ft-0 in. and carries a superimposed live load of 2.7 kips/ft. The tendon is straight and located 9 in. below the neutral axis of the beam. The pre stress force is 250 kips. Neglect pre stress losses and use the gross concrete section properties. Use the method of superposition for the solution.