Heat Straightening Damaged Steel Plate Elements

The fundamental element of any structural steel shape is the flat plate. Damage to bridge structures consists of these plate elements, in combination, bent about their strong and/or weak axes. The purpose of this paper is to describe experimental and analytical research on heat straightening as applied to plates and to present related engineering criteria for its use. An experimental program was conducted to evaluate the response of plates to heat straightening and to identify important parameters influencing behavior. Over 300 heats were applied to a variety of plates. The primary factors influencing straightening were the angle of the vee heat, steel temperature during heating, and external restraining forces. The plastic rotation after heating was directly proportional to these parameters. To aid engineers in predicting plate movements during heat straightening, a simple mathematical formula was developed. This equation relates the average plastic rotation per vee heat to vee angle, steel temperature, magnitude of restraining force, coefficient of thermal expansion, and yield stress. The formula compares well to the experimental data and is the first simple formula available that includes the parameters of heating temperature and magnitude of restraining force. The form of this analytical approach also will lend itself toward extensions, including the behavior of rolled shapes, axially loaded members, and composite and noncomposite girders.