Principles ~ the well known properties of concrete are that it has
high compressive strength and low tensile strength. The basic
concept of reinforced concrete is to include a designed amount of
steel bars in a predetermined pattern to give the concrete a
reasonable amount of tensile strength. In prestressed concrete a
precompression is induced into the member to make full use of its
own inherent compressive strength when loaded. The design aim is
to achieve a balance of tensile and compressive forces so that the
end result is a concrete member which is resisting only stresses
which are compressive. In practice a small amount of tension may
be present but providing this does not exceed the tensile strength
of the concrete being used tensile failure will not occur.
Prestressed Concrete