Editor's Note

摘要

The primary themes of the papers appearing in this issue of the Journal are metal structures and structural identification. The remaining papers cover three technical areas: concrete structures, wood structures, and special design issues.rnThe primary themes of the papers appearing in this issue of the Journal are metal structures and structural identification. The remaining papers cover three technical areas: concrete structures, wood structures, and special design issues.rnThis opening issue of the Journal for 2009 begins with a two-part paper by Lee et al. revisiting the anchoring mechanism believed to be the source of the postbuckling strength of plate girder web panels. The first paper in the series is titled "Further Insights into Postbuckling of Web Panels. I: Review of Flange Anchoring Mechanism." The study finds that the anchoring mechanism does not develop, regardless of the weight of the flanges, without transverse stiffeners that have sufficient axial stiffness necessary to keep the flanges from moving inwards toward the web panel during the anchoring action. In practical plate girders, the contribution of the flange anchoring mechanism to the postbuckling strength is negligibly small, not because the flanges are too flexible to function as anchors, but because the transverse stiffeners are axially too flexible to support the flanges. Taking advantage of the flange anchoring mechanism in practical design is hence impractical, if not impossible. The follow-on study "Further Insights into Postbuckling of Web Panels. II: Experiments and Verification of New Theory" highlights the source of plastic hinge-like failure modes often observed in tests. It is found that such failure modes, accompanied by severe flange deformations, are not due to the anchoring action of the flanges, but to direct shear force acting on the flange cross sections. The study also examines why the horizontal anchoring mechanism cannot develop in interior panels or in end panels with a heavy end stiffener. Findings from the overall study reveal that the anchoring mechanism is virtually nonexistent in normal plate girders. It is also found that a tension field can develop in the end panel, and therefore the writers recommend that any restriction contrary to this observation found in current design codes be repealed.