To easily drain water owing to rain or the like from the surface of a hollow by a method wherein a continuous groove-like recessed part is provided at a position corresponding to a joint of an inner plate-like rib an outside surface of a top board or/and a baseplate.
In this hollow structure with a rib having a groove-like recessed part, an outer peripheral plate-like rib is provided so that peripheral ends corresponding to respective four sides are integrally connected to respective four sides of a top board 1 and a baseplate 2 of a tetragon arranged in parallel so as to correspond to their faces to form side walls, and their inside is hollow. Then, further a groove-like recessed part 6 of the almost same width of a rib thickness is provided to a position corresponding to a joint of an inner plate-like rib 4 of an outer surface of the top board 1, and a groove-like recessed part 6' is provided on both sides of an inner plate- like extended rib 4' along that at a rootpart of the baseplate 2 of the inner plate-like extended rib 4'. Then, the groove-like recessed part 6 of the almost same width as the rib thickness is provided also to a position corresponding to the joint of the inner plate-like rib 4 wherein the inner plate-like extended rib 4' of the baseplate 2 is not provided.
KITAYAMA TAKEO
MATSUBARA SHIGEYOSHI
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