The need for the use of high strength concrete and tensile steel in Pre stressed concrete
· High strength concrete is necessary for prestress concrete as the material offers highly resistance in tension, shear bond and bearing. In the zone of anchorage the bearing stresses being hired, high strength concrete is invariably preferred to minimizing the cost. High strength concrete is less liable to shrinkage cracks and has lighter modulus of elasticity and smaller ultimate creep strain resulting in a smaller loss of prestress in steel. The use of high strength concrete results in a reduction in a cross sectional dimensions of prestress concrete structural element with a reduced dead weight of the material longer span become technically and economically practicable.
· Tensile strength of high tensile steel is in the range of 1400 to 2000 N/mm2 and if initially stress upto 1400 N/mm2 their will be still large stress in the high
tensile reinforcement after making deduction for loss of prestress. Therefore high tensile steel is made for prestress concrete.
Advantages of PSC construction
· In case of fully prestressed member, which are free from tensile stresses under working loads, the cross section is more efficiently utilized when compared with a reinforced concrete section which is cracked under working loads.
· The flexural member is stiffer under working loads than a reinforced concrete member of the same length.
· Pre tensioning: A method of Pre stressing concrete in which the tendons are tensioned before the concrete is placed. In this method, the prestress is imparted to concrete by bond between steel and concrete.
· Post tensioning: A method of pre stressing concrete by tensioning the
tendons against hardened concrete. In this method, the prestress is imparted to concrete by bearing.
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