| 摘要 |
PROBLEM TO BE SOLVED: To facilitate maintenance as a result of causing little looseness because of causing no concentration of elongation and compressive stress between a reinforcing rib and a reinforcing rib on the outer peripheral edge of a cover body even when a vehicle passes through a surface of the cover body by dispersing the elongation and the compressive stress between the reinforcing rib and the reinforcing rib on the outer peripheral edge of the cover body in a well- balanced state by a stress dispersing part. SOLUTION: In this cover body for an underground structure, a locking projection strip is arranged on the reverse peripheral edge of a board body, the required number of reinforcing ribs are projected on the reverse, both end of these reinforcing ribs are continuously arranged on an inner wall surface of the locking projection strip, the stress dispersing part is integrally formed between the reinforcing rib and the reinforcing rib on the reverse of the board body, and this stress dispersing part is continuously arranged on the inner wall surface of the locking projection strip. COPYRIGHT: (C)2003,JPO
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