BOX CULVERT

PROBLEM TO BE SOLVED: To provide a box culvert capable of exhibiting a stable performance to a sectional force generated in a top wall part, surely reinforcing the corner angle part between the top wall part and a side wall part, and being manufactured in the same method even with a small change such as inner hollow lateral dimension or the like. SOLUTION: In this box culvert 1, the hollow part 5-side surface of the top wall part 2 is formed into a gentle circular shape toward the upper ends of both side wall parts 3, so that the vicinities of the side wall parts 3 are thickened, and the vicinity of about the center between the side wall parts 3 is linearly formed. The sectional area in the vicinities of the side wall parts 3 of the top wall part 2 is increased to exhibit the stable performance to the sectional force, and the corner angle part between the top wall part 2 and the side wall part 3 is surely reinforced in corporation with a strain member 7 arranged eccentrically to the top wall part 2. The vicinity of about the center between the side wall parts 3 is linearly formed, and the linear position is set to a movable part, whereby the manufacturing form for the top wall part 2 can be varied, so that products of different inner hollow width dimensions can be manufactured by use of a single form.