a What is anchorage slip? How do you compute the loss of stress due t…

Question

a What is anchorage slip? How do you compute the loss of stress due to anchorage slip?

b Differentiate between full prestressing and partial prestressing.

c A prestressed concrete beam 250 mm wide and 360 mm deep has a span of 12 m. The beam is prestressed by steel wires of area 350 mm² provided at a uniformly eccentricity of 60 mm with an initial prestress of 1250 N/mm². Determine the percentage loss of stress in the wires if the beam is a pretensioned beam and post tensioned beam. Take Es = 210 KN/mm², Ec = 35 KN/mm². Ultimate creep strain = 45 X 10⁻⁶ mm/mm per N/mm² for pretensioned beam and 22 X 10⁻⁶ mm/mm per N/mm² for post tensioned beam. Shrinkage of concrete = 300 x 10⁻⁶ for pretensioned beam and 215 X10⁻⁶ for post tensioned beam. Relaxation of steel stress = 5% of the initial stress, Anchorage slip = 1.25 mm, Friction coefficient for wave effect K = 0.00015 per m.