Heat curving HPS 485W bridge I-girders

Abstract

Heat curving is widely used for fabricating curved steel bridge I-girders. Curving is accomplished by asymmetric heating of the flanges of the straight girder. Heat is applied along the girder length continuously or intermittently with the heated width varying from 1/12 to 1/4 of the flange width depending on the curvature. Curvature develops after the girder cools to ambient conditions. Current practice limits the maximum temperature to 620°C for conventional Grades 250 and 345 steels. The "Guide for Highway Bridge Fabrication with HPS 485W Steel" recommends investigating heat curving of HPS 485W at 705°C. This paper evaluates the validity of the 705°C temperature using non-linear finite element analysis. Other fabrication issues relating to heat curving stiffened and hybrid girders are also addressed. Results show that the maximum temperature can be somewhat lower. Stiffeners may reduce the curvature by up to 10% while hybrid girders with top and bottom flanges made of different steel grades require different heating profiles.