Theoretical Stresses and Strains from Heat Curving

Horizontally curved steel girders for curved highway bridges can be economically fabricated by building a straight girder and then heating appropriate flange edges to induce a residual curvature after cooling. The results of a theoretical investigation of the residual stress, strain, and curvature due to this heat-curving process are presented. The analytical model used a perfect elastic-plastic, temperature-dependent stress-strain relationship for the steel, and temperature profiles in the girder flanges based on heat-transfer theory for a semi-infinite plate. The effects of maximum edge temperatures to 1,150°F over increasing widths of the flanges of a typical girder were determined. The residual stresses after heat curving were tensile near the flange edge and compressive elsewhere, except near the center of the flange, where tensile stress sometimes remained. The final curvature, which was determined from the residual strain distribution, generally increased with maximum temperature.