Effect of Strain Hardening on the Flexural Resistance of Composite Plate Girders Using HSB600 High-Performance Steel in Positive Bending

Abstract

This study presents a new nominal flexural resistance of composite I-girder sections using high-performance steel, HSB600, in the positive bending region. Unlike conventional steels, HSB600 undergoes strain hardening immediately after yielding. To compare the flexural behavior of composite girder sections using HSB600 with that of conventional composite steel girder sections, a moment-curvature analysis was performed. To take into account the effects of strain hardening on the flexural resistance, the strain-hardening plastic moment was introduced as a substitute for the full plastic moment. An extensive parametric study using the strain compatibility method was conducted for a wide range of composite girder sections, and the relationship between the ratio of the strain-hardening plastic moment to the full plastic moment and the ductility ratio was determined. On the basis of the results of the parametric study, a factor that accounts for the strain-hardening effects is suggested as a function of the ductility ratio. A new nominal flexural resistance for the composite HSB600 girder sections is then proposed, defined as the product of the nominal flexural resistance in the AASHTO LRFD Bridge Design Specifications and the strain-hardening factor.