METHOD FOR DESIGNING STEEL BOX GIRDER AND STEEL BOX GIRDER

To provide a steel box girder in which horizontal stiffeners are safely omitted without increasing the web thickness from a steel box girder designed with horizontal stiffeners.SOLUTION: A method of designing a steel box girder includes: an initial design step for designing a temporary steel box girder to satisfy the requirements of Specifications for Highway Bridges by arranging one stage of horizontal stiffeners on each of webs 16 and 18; an ultimate load bearing capacity confirming step for confirming that an ultimate load bearing capacity Mmax of a horizontal stiffener omitted steel box girder after omitting all the horizontal stiffeners from the temporary steel box girder designed in the initial design step is larger than a yield bending moment My without considering buckling of the horizontal stiffener omitted steel box girder; and a maximum out-of-plane displacement confirming step for confirming that a maximum out-of-plane displacement γ generated in the webs 16 and 18 when the bending moment obtained by dividing the ultimate load bearing capacity Mmax by 1.7 is applied to the horizontal stiffener omitted steel box girder is smaller than a manufacturing allowable value a specified in the Specifications for Highway Bridges.SELECTED DRAWING: Figure 1 【課題】水平補剛材を設けて設計された鋼製箱桁から、ウェブ厚を大きくすることなく、水平補剛材を安全に省略した鋼製箱桁を提供する。【解決手段】ウェブ１６、１８それぞれに水平補剛材を１段配置して道路橋示方書の規定を満たすように仮の鋼製箱桁を設計する初期設計工程と、前記初期設計工程で設計した前記仮の鋼製箱桁から前記水平補剛材を全て省略した後の水平補剛材省略鋼製箱桁の終局耐荷力Ｍmaxが、前記水平補剛材省略鋼製箱桁の座屈を考慮しない降伏曲げモーメントＭyより大きいことを確認する終局耐荷力確認工程と、前記終局耐荷力Ｍmaxを１．７で除した曲げモーメントが前記水平補剛材省略鋼製箱桁に加わった時のウェブ１６、１８に生じる最大面外変位γが道路橋示方書に規定されている製作許容値ａよりも小さいことを確認する最大面外変位確認工程を有する。【選択図】図１