| 摘要 |
In order to span an access pit or manhole having a clear opening of relatively large area, one or more I-section steel beams are laid across the opening so as to divide the area to be covered into a number of smaller areas. One or more frame members, each of which is shaped so as to support parts of two covers or gratings which are adjacent and on opposite sides of the associated beam, are then positioned directly above the center line of the or each beam and bolted to the beam. Finally the areas between the or each beam and the sides of the pit or manhole, and between the beams themselves, are covered by covers or gratings supported by the frame members. Such an arrangement ensures that eccentric loading of the beams does not occur under heavy loading conditions.
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