Improved Characterization of the Flexural and Axial Compressive Resistance of Noncomposite Longitudinally Stiffened Welded Steel Box-Section Members

摘要

There exists great potential for improvement of existing methods for calculating the flexural and axial compressive resistance of longitudinally stiffened welded steel box-section members, to achieve gains in the accuracy of their representation of the limit states responses as well as greater generality and ease of their design application. A good quantification of the ultimate compressive resistance of longitudinally stiffened plates is crucial for accurate characterization of the flexural and axial compressive resistance of these member types. This paper summarizes the conceptual and theoretical development of new methods for characterization of the ultimate compressive resistance of longitudinally stiffened plates, and the flexural and axial compressive resistance of longitudinally stiffened welded box-section members. The proposed method for calculating the plate compressive resistance is derived using an orthotropic plate idealization, but is expressed as a designer-friendly, intuitive column on elastic foundation model. This model considers the contributions from longitudinal stiffener flexure, transverse plate bending, and plate torsion. The proposed method for calculating member flexural resistance recognizes the inability of longitudinally stiffened flange plates to sustain large inelastic compressive strains beyond their maximum resistance, and therefore limits the flexural resistance of box sections with a longitudinally stiffened compression flange to the first yield of the compression flange in the effective cross-section. For sections involving early yielding of the tension flange, the member response is addressed rigorously via the direct calculation of the yield moment to the compression flange, considering the early yielding on the tension side of the neutral axis, and considering hybrid web, slender web and unstiffened slender or longitudinally stiffened compression flange effects as applicable. The paper presents a parametric study of longitudinally stiffened welded box columns whose failure mode involves combined flexural and local buckling, for which there is no experimental or finite element simulation data in the literature. The predictions using the proposed methods correlate well with the results from finite element test simulations, and with data compiled from experimental tests.