Minimizing Warpage & Distortion
Steel being galvanized is exposed to a wide temperature range from ambient to 850 F. Because parts are immersed at an angle, uneven heating and cooling occur. This exposure to temperature variations allows the steels internal stresses to be relieved at different times.
Some fabricated structures and assemblies may distort at the galvanizing temperature as a result of relieving stresses induced during steel production and in subsequent fabricating operations. In general, the potential for warpage/distortion can be greatly reduced through design and production engineering measures to avoid high internal stresses. Starting discussions between the designer, fabricator, and galvanizer early in the design process is good practice to ensure alternative design features can be incorporated to prevent issues.
The guidelines for minimizing distortion and warpage are provided in ASTM A384, Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies. This section will review design practices and fabrication techniques that are known to increase the susceptibility for warpage and distortion and how they should be minimized or eliminated in bridge design wherever possible.