prestressed road bridge of span 16.74 m consists ofa
concrete slab of 420 mm thick with parallel post-tensioned cables,in each of which the force
at transfer is 440 kN. If the bridge is required to support auniformly distributed applied load
of 43.37kN/m2
, with tensile stress in the concrete not exceeding
0.85 N/mm2
at any time. Calculate the maximum horizontal spacing of thecables, their
distance from the soffit of the slab at mid-span and their lowestpossible position at
supports. Assume 15 % loss of prestress after transfer. Alsocalculate the number of steel
wires used in each cable with the permissible stress of 1200N/mm2
for 7 mm diameter steel
wire. Assume the density of the concrete is 24 kN/m3
.
