When thin tubular girder bridge is applied to a curved bridge, basically, like usual tubular girder bridge, if, you can think and design, but when anyway the matter worried about by thin tubular girder bridge is enumerated, it seems to be the next.(1) Because it's an oblong section, doesn't a lateral torsion buckling like hanketa form?(2) Doesn't the addition stress intensity by the curvature of the flange form like curved line hanketa?(3) Can I resist by a crossbeam of small section to a twisting moment of a center figure?(4) Doesn't the excessive addition bending unit stress occur to a floor system?Among these, crossbeam sectional force by usual lattice analysis can estimate about a crossbeam of(3). When radius of curve was small, it's to arrange an interval small as a crossbeam in a rather big section, not the aspect like the usual II section steel, and I'm prepared. It'll be a problem of curved bridge in general later about additional stress of a floor system of(4), and it can be said that there are no problems that a thin box figure reason is special.A study result about the addition stress intensity by the lateral torsion buckling of(1) and the curvature of(2) is indicated here.