Keesei Lee

Spacing of Intermediate Diaphragms Horizontally Curved Steel Box Girder Bridges considering Bending-distortional Warping Normal Stress Ratio

Although distortions of horizontally curved box girder are more susceptible than which of the straight girder due to curvature effect, current domestic design standards does not present spacing of intermediate diaphragms for the curved box girder. In this study, parametric studies for straight and curved box girder considering distortional warping normal stresses based on linear finite element analysis were carried out. Single span curved girders were chosen for analysis based on current domestic bridge data with 1-6 of solid intermediate diaphragms, 0-30 degree of subtended angle, 30m and 60m of span length and 2-3m of flange width and web height. The adequate spacing of diaphragms for the box girder were suggested considering subtended angles and bending and distortional warping normal stress ratios with 5%, 10%, 15% and 20%. The analysis results were also compared to a current design standard and suggested spacing of diaphragm were evaluated.

Effects of flange and web slenderness ratios on elastic flange local buckling of doubly symmetric I-girders

Increasing the strength of structural materials allows their self-weight to be reduced and this, in turn, enables the structures to satisfy esthetic requirements. The yield strength of high-performance steel is almost 480 MPa, which is approximately 50% higher than that of general structural steel. The use of high strength materials, however, makes the sections more slender, which can potentially result in significant local stability problems. The strength of slender element sections might be governed by their elastic buckling behavior, and the elastic buckling strength is very sensitive to the boundary conditions. Because the web provides the boundary conditions of the compressive thin-flange, the stiffness of the web can affect the elastic buckling strength of the flange. In this study, therefore, the effects of the flange and web slenderness ratios on the elastic flange local buckling of I-girders subjected to a pure bending moment were evaluated by finite element analysis (FEA). The analysis results show that the elastic local buckling strength and buckling modes were affected not only by the web support conditions, but also by the flange and web slenderness ratios.

An Analytical Study of Flange Local Buckling of Horizontally Curved I-Girders for Estimate Resonable Stress Gradient

Abstract Horizontally curved I-girders are subjected to not only bending moments but also torsional moments. The torsional moment of the plate girder is addition of St. Venant torsion and non-uniform torsion. In the flange of I-shaped plate girder, a kind of open-section, the normal stresses is not distributed uniformly due to the non-uniform torsion. Because of that, one of compression flange tip can be yielded faster than the flange of general straight girder.In other words, the flange local buckling strength is decreased when the girder has initial curvature. In this paper,the numerical analysis is conducted to investigate the average stresses in flange for curved girders. The subtended angle and slenderness ratio are taken as parameters. Keywords : Curved I-girder, Flange local buckling, Stress gradient 본 논문은 건설교통부가 출연하고 한국건설교통기술평가원에서 위탁시행한 건설교통기술촉진연구사업의 연구비 지원(12기술혁신B01-곡선 강교량의 합리적인 LRFD 설계기술 개발)에 의해 수행됨 * Corresponding Author : Young-Jong Kang(Korea Univ.)Tel: +82-2-927-7715 email: yjkang@korea.ac.krReceived August 18, 2015 Revised September 2, 2015 Accepted October 8, 2015 Published October 31, 2015