==== ==== Acerca de vigas pretensadas: http://www.ingeniero-de-caminos.com/2012/02/vigas-pretensadas-hormigon.html ==== ==== There are two basic concepts which are generally applied in practice in the field of structural concrete construction and they are; (1) conventionally reinforced and (2) Prestressed concrete. In prestressed concrete we find the predetermined forces forced on the concrete structural member by special high-tensile steels giving maximum strength with a minimum quantity of steel and this gives an outcome of significant savings in steel tonnage and cost. These anticipatory prestressing forces are calculated and positioned to mitigate the anticipated stresses that occur during the service loading of the member, thus results in reducing the net final stresses developed and allowing a noteworthy decrease in the essential size of the concrete elements. In general, the prestressing steel strength is approximately 4.5 times tough than regular reinforcing steel. We find that in long-line pre-casting mass-production operations the Pre-stressed beams and slabs are the most economically applied. Large reductions in labor, formwork, and hardware costs can be realized due to the inherent efficiencies of these mass-production techniques, Also there are floating platforms to exploit the greatest source of energy in the world, for the support of ocean thermal energy conversion (OTEC) plants are also being planned with prestressed concrete for the main hull structure. The economic and environmental benefits of prestressed concrete can be significant if a coordinated Structural Engineering educational program is given impetus. Advantages of Prestressed concrete 1.Section remains uncracked under service loads 2.High span-to-depth ratios 3.Suitable for precast construction Types of Prestressing of concrete (1)External or internal prestressing This classification is based on the location of the prestressing tendon with respect to the concrete section. (2)Pre-tensioning or post-tensioning This is the most important classification and is based on the sequence of casting the concrete and applying tension to the Tendons. (3)Linear or circular prestressing This classification is based on the shape of the member prestressed.
(4)Full, limited or partial prestressing Based on the amount of prestressing force, three types of prestressing are defined. (5)Uniaxial, biaxial or multi-axial prestressing As the names suggest, the classification is based on the directions of prestressing a member. Article Source: http://EzineArticles.com/?expert=Rtsh_Patel
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