• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.205-217
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• 2014

In this study, flexural strength and ductility requirements of composite hybrid steel I-girder with its HSB(high performance steel for bridge) applied to tension flanges are examined in positive bending. In AASHTO LRFD specification, flexural strength and ductility requirements of composite I-girder in positive bending are specified in terms of plastic moment and plastic neutral axis that are derived from plastic behavior of conventional steel. However, plastic zone cannot be defined clearly from the stress-strain behavior of HSB unlike the behavior of conventional steel. Therefore, through idealized stress-strain curves of HSB, the plastic moment of composite hybrid steel I-girder with its HSB applied to tension flanges is defined by assuming the plastic zone of HSB. By using the consequences of numerical analysis regarding arbitrary cross-sections that have various dimensions, ductility requirements and flexural strength of composite hybrid I-girder with its HSB applied to tension flange are proposed.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.385-395
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• 2011

The flexural strength of composite HSB hybrid I-girders under positive moment is investigated by the moment-curvature analysis method to evaluate the applicability of the current AASHTO LRFD design specification to such girders. The hybrid girders are assumed to have the top flange and the web fabricated from HSB600 steel and the bottom flange made of HSB800 steel. More than 6,200-composite I-girder sections that satisfy the section proportion limits of AASHTOL RFD specifications are generatedby the random sampling technique to consider a statistically meaningful wide range of section properties. The flexural capacities of the sections are calculated by the nonlinear moment-curvature analysis in which the HSB600 and HSB800 steels are modeled as an elastoplastic, strain-hardening material and the concrete as CEB-FIP model. The effects of ductility ratio and compressive strength of concrete slab on the flexural strength of composite hybrid girders make of HSB steels are analyzed. Numerical results indicated that the current AASHTO-LRFD equation can be used to calculate the flexural strength of composite hybrid girders fabricated from HSB steel.