Heat Straightening Rolled Shapes

Abstract

The process of heat straightening damaged rolled shapes is based on a logical extension of the straightening of plates. When damaged, some plate elements are bent about their strong axis, some about their weak axis, and some about both. The overall effect on a rolled shape is damage that is a combination of one or more of the following fundamental damage categories: (1) Category S denotes primary bending about the major or strong axis; (2) Category W denotes primary bending about the minor or weak axis; (3) Category T denotes torsion or twisting of a member about its longitudinal axis; and (4) Category L denotes localized damage to plate elements in the form of bulges, buckles, and crimps. The purpose of this paper is to examine the behavior of rolled shapes during heat straightening with the focus on Category S and Category W types of damage. For repair of such damage, simple heating patterns are used in combination. The use of vee, line, and strip heats are illustrated for both Category S and Category W damage. Over 300 heats were applied to 30 rolled shapes to document the behavior of heat-straightened angles, channels, and wide flange beams. The experimental data suggested that the amount of straightening during one heating cycle is a function of vee angle, magnitude of jacking force, shape of the cross section, and stress distribution due to jacking. A mathematical formula to predict the amount of straightening per heat was developed. The form of this formula was to modify the formula for a single plate element by including a load factor, shape factor, and stress factor. This approach produced reasonable agreement with the experimental data.