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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