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A mechanical floor, mechanical penthouse, or mechanical level is a story of a high-rise building that is dedicated to mechanical and electronics equipment. "Mechanical" is the most commonly used term, but words such as ''utility'', ''technical'', ''service'', and ''plant'' are also used. They are present in all tall buildings including the world's tallest skyscrapers with significant structural, mechanical and aesthetics concerns. While most buildings have mechanical rooms, typically in the basement, tall buildings require dedicated floors throughout the structure for this purpose, for a variety of reasons discussed below. Because they use up valuable floor area (just like elevator shafts), engineers try to minimize the number of mechanical floors while allowing for sufficient redundancy in the services they provide. As a rule of thumb, skyscrapers require a mechanical floor for every 10 tenant floors (10%) although this percentage can vary widely (see examples below). In some buildings they are clustered in groups that divide the building into blocks, in others they are spread evenly through the structure, while in others still they are mostly concentrated at the top. Mechanical floors are generally counted in the building's floor numbering (this is required by some building codes) but are accessed only by service elevators. In some legislations they have been excluded from maximum floor area calculations, leading to significant increases in building sizes; this is the case in New York City.〔(greatgridlock.net )〕 Sometimes buildings are designed with a mechanical floor located on the thirteenth floor, to avoid problems in renting the space due to superstitions about that number. ==Structural concerns== Some skyscrapers have narrow building cores that require stabilization to prevent collapse. Typically this is accomplished by joining the core to the external supercolumns at regular intervals using outrigger trusses. The triangular shape of the struts precludes the laying of tenant floors, so these sections house mechanical floors instead, typically in groups of two. Additional stabilizer elements such as tuned mass dampers also require mechanical floors to contain or service them. This layout is usually reflected in the internal elevator zoning. Since nearly all elevators require machine rooms above the last floor they service, mechanical floors are often used to divide shafts that are stacked on top of each other to save space. A transfer level or skylobby is sometimes placed just below those floors. Elevators that reach the top tenant floor also require overhead machine rooms; those are sometimes put into full-size mechanical floors but most often into a mechanical penthouse, which can also contain communications gear and window-washing equipment. On most building designs this is a simple "box" on the roof, on others it is concealed inside a decorative spire. A consequence of this is that if the topmost mechanical floors are counted in the total, there can be no such thing as a true "top-floor office" in a skyscraper with this design. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「mechanical floor」の詳細全文を読む スポンサード リンク
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