| 摘要 |
In the case of a conventional method wherein the ends of minor beams are pinned, no bending moment can be borne at the ends of the minor beams, resulting in large deformations being caused. Meanwhile, in the case of joining minor beams to major beams by welding, as has been proposed so far, the amount of welding is high, and since the webs of the minor beams are pinned, the strength pertaining to all cross sections of the minor beams fails to be secured at the ends of the minor beams. Furthermore, piping in a ceiling uses a large number of sleeves which pass through major beams, leading to increases in costs and construction periods. Various studies were made regarding all such problems, with the consequence that minor beams are made to intersect major beams, with one type of beams placed on top of the other type of beams, resulting in making it possible to use long minor beams; that stiffeners or doublers are adopted for the joining of the ends of the minor beams, said stiffeners being passed through minor beams, and said doublers being used, as strength members, on the minor beam flange inner surfaces; that as a result, it became possible to make use of the section moduli and the moments of inertia of areas of all cross sections of the minor beams; and that in consequence, it was made possible to reduce the sizes of the minor beams and to significantly decrease sleeves for piping. Furthermore, upward-facing haunches are used on major beams, with the result that it is made possible to reduce the sizes of the major beams.
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