(57) The longitudinally compressive and tensile proportionality limits and ultimate strengths
of an elongated structural member are increased by applying to the member a longitudinally
compressive load which is close to its maximum load. In order to prevent buckling
of the member under such a load, the member is confined in an encasement which allows
the member to yield longitudinally without bending. By applying to the member a longitudinally
compressive load much greater than the member's original (i.e. untreated) ultimate
compressive strength, both the ultimate strengths and the proportionality limits of
the member are increased. In addition, application of a longitudinally compressive
load close to or greater than the original ultimate compressive strength of the member
also increases the straightness of the member and frees the member of residual stresses.
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