The horizontal prestress at the centroid of a concrete beam of rectangular crosssection 120 mm and 250 mm, is 7 N/mm2 and the maximum shearing force on the beam is 70 kN. Calculate the maximum principal tensile stress. What is the minimum vertical prestress required to eliminate this principal tensile stress?

For a simply supported prestressed concrete beam, compute the stress in the top fiber at the centerline. Properties of the beam are: Width of the beam, b: 222 mm; Depth of the beam, d: 396 mm; Eccentricity of the beam, e: 177 mm; Prestressing Force, P: 541 KN; Superimposed Load, w: 8 KN/m; Length of the beam, L: 11 m. Stress is in unit MPa. Write only the value of your final answer. w (including selfweight) 000