| 摘要 |
The gutter (1) has a ventral face (6) directed towards the ground (5), and a front face (7) above the plane of the ventral face. The gutter has a casing (8) constituted by two walls (9,10) which extend parallel to the two faces. The casing has external faces (9A,10A) parallel to which extend two webs (11,12) of the external casing (13). The two casing webs are constituted from a metallic plate (13A) with a transverse L section. The plate is longitudinally stiffened, to oppose its bending, by a fold (14). This fold forms a rib which extends a certain distance (D) under the plane of the encasement web of the ventral wall.
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