INVESTIGATION OF HEAT-CURVED GIRDERS

THE USAGE OF HORIZONTALLY CURVED STEEL GIRDERS IS INCREASING BECAUSE IT PERMITS LONGER SPANS, SIMPLIFIES THE CONSTRUCTION DETAILS FOR THE CONCRETE DECK, AND RESULTS IN THE AESTHETIC STRUCTURE. CURVED GIRDER CAN BE FABRICATED IN THE FOLLOWING WAYS: (1) FLAME CUTTING THE FLANGES TO THE DESIRED CURVATURE FROM RECTANGULAR PLATES, AND THEN FITTING AND WELDING THE GIRDER, (2) FABRICATING A STRAIGHT GIRDER AND COLD BENDING OR (3) FABRICATING A STRAIGHT GIRDER AND THEN HEATING THE FLANGE EDGES ON ONE SIDE OF THE GIRDER TO INDUCE A RESIDUAL CURVATURE AFTER COOLING. THE HEAT CURVING METHOD IS CONSIDERED TO BE AN ECONOMICAL METHOD FOR MOST GIRDERS SINCE ONLY NORMAL SCRAP LOSSES ARE INCURRED AND EXISTING JIGS AND FIXTURES MAY BE USED IN FABRICATION. A COMBINED ANALYTICAL AND EXPERIMENTAL INVESTIGATION WAS CONDUCTED TO DETERMINE THE EFFECT OF HEAT CURVING ON THE RESIDUAL STRESS, STRAIN, AND CURVATURE ON A TYPICAL BRIDGE GIRDER. THESE ANALYSES ARE THEN APPLIED TO A STUDY OF A SPECIFIC GIRDER. THE CONTINUOUS HEAT-CURVING PROCESS PRODUCES A CONTINUOUSLY CURVED GIRDER WITH A CURVATURE THAT CLOSELY APPROXIMATES THE DESIRED CIRCULAR CURVATURE. THE FINAL RESIDUAL CURVATURE IS REACHED WHEN THE FLANGES COOLED TO A UNIFORM TEMPERATURE. THE RESIDUAL STRESSES AFTER HEAT CURVING ARE GREATER THAN BEFORE IN ALL PARTS OF THE GIRDER EXCEPT AT THE MID-WIDTH OF THE FLANGE WHERE THE INITIAL STRESS DUE TO WELDING IS REDUCED. ALONG THE HEATED FLANGE EDGES TENSILE RESIDUAL STRESS IS NEARLY EQUAL TO THE YIELD POINT. AT THE OPPOSITE FLANGE TIPS, THE TENSILE RESIDUAL IS SOMEWHAT LESS. THE COMPRESSIVE RESIDUAL STRESS IN THE WEB CAUSES THE WEB TO BOW. THE RESIDUAL STRAIN VARIES LINEARLY ACROSS THE FLANGE EXCEPT IN THE HEATED WIDTH WHERE THE DISTRIBUTION IS AFFECTED BY THE PLASTIC FLOW. THE HEAT-CURVING OPERATION CAUSED A 15% INCREASE IN THE YIELD POINT AT THE HEATED EDGE, A 10% DECREASE AT AN INTERIOR POSITION ON THE FLANGE AND LITTLE CHANGE ELSEWHERE. THE EXPERIMENTAL BEHAVIOR OF THE GIRDER DURING THE HEAT-CURVING OPERATION WAS IN AGREEMENT WITH THAT PREDICTED IN THE ANALYTICAL INVESTIGATION.

• Supplemental Notes:
  • pp 209-253, 35 FIG, 10 REF
• Authors:
  • Brockenbrough, R L
• Publication Date: 1968-12

Media Info

• Serial:
  • Am Assoc State Highway Officials Proc

Subject/Index Terms

• TRT Terms: Aesthetics; Bending; Curvature; Curves (Geometry); Fabrication; Flame cutting; Flanges; Girders; Heating (Structures); Metal working; Residual stress; Tension
• Uncontrolled Terms: Horizontal curvature; Tensile stress
• Old TRIS Terms: Curved steel girders; Metal bending
• Subject Areas: Bridges and other structures; Highways;

Filing Info

• Accession Number: 00209226
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 26 1970 12:00AM