Effect of Residual Stresses in H-shapes on the Performances

Abstract

In hot rolled H-shapes residual stresses are generated during cooling due to the different cooling rate between the web and flanges. The residual stresses in beams and colums are reported to have bad effects on the performances of beams. In this paper the following effects of residual stresses in H-shapes are studied.
(1) Cracking on flame-cutting (Initiation and propagation of brittle cracks in web after flamecutting)
(2) Deflection of T-shaped beams cut from H-shapes
(3) Deterioration of bending performance
It is found that the residual stresses give bad effects on the items mentioned above. However, the beams in which the residual stresses are reduced by the forced cooling on flange are improved in these performances.
(a) Deflection of T-shapes becomes very small on cutting H-shapes along web center
(b) Bending performance becomes similar to that of the ideal H-beams which have no residual stresses
It also becomes clear that the initiation of micro-cracks can not be prevented on flame-cutting, even if a small magnitude of residual stresses exists. The micro-cracks, however, do not propagate when the residual stresses are small.