11-03-2018, 01:45 PM
Prestressed concrete is high strength concrete reinforced with high strength wires (or cables or rods) in which the wires are so tensioned as to induce a desirable compressive force in the concrete.
History
Prestressed concrete was first made about 1880; it was not a success because the steel available had a low strength (mild steel) and could not be stretched sufficiently to overcome the creep and shrinkage effects in the concrete, and the tensile creep of the steel. The creep of the concrete induced a shortening of the concrete about equal to the extension of mild steel bars stressed to a working load of 9 tons per sq. in, so that although prestressed concrete could be made, it could not be made to last. The lasting properties of prestressed concrete, that is. concrete which remained prestressed so that it could be used commercially, only became available when high strength steel and high strength concretes were developed and when, with these materials combined, an engineer appreciated
that creep and shrinkage were time dependent phenomena which...
for more detail .....
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History
Prestressed concrete was first made about 1880; it was not a success because the steel available had a low strength (mild steel) and could not be stretched sufficiently to overcome the creep and shrinkage effects in the concrete, and the tensile creep of the steel. The creep of the concrete induced a shortening of the concrete about equal to the extension of mild steel bars stressed to a working load of 9 tons per sq. in, so that although prestressed concrete could be made, it could not be made to last. The lasting properties of prestressed concrete, that is. concrete which remained prestressed so that it could be used commercially, only became available when high strength steel and high strength concretes were developed and when, with these materials combined, an engineer appreciated
that creep and shrinkage were time dependent phenomena which...
for more detail .....
register as member and login to download attachment [pdf] by Right-click the pdf link and Select “Save link as”