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本帖最后由 Gouken 于 2011-7-24 20:47 编辑
CTBUH Height Criteria
What is a tall building? How is a building's height measured? What do terms like "supertall" and "mixed-use" actually mean? These and other questions are answered in the CTBUH Height Criteria, the official rules whereby tall buildings are defined and heights are measured.
What is a Tall Building?
There is no absolute definition of what constitutes a “tall building.” It is a building that exhibits some element of “tallness” in one or more of the following categories:
a) Height relative to context
It is not just about height, but about the context in which it exists. Thus whereas a 14-story building may not be considered a tall building in a high-rise city such as Chicago or Hong Kong, in a provincial European city or a suburb this may be distinctly taller than the urban norm.
b) Proportion
Again, a tall building is not just about height but also about proportion. There are numerous buildings which are not particularly high, but are slender enough to give the appearance of a tall building, especially against low urban backgrounds. Conversely, there are numerous big/large footprint buildings which are quite tall but their size/floor area rules them out as being classed as a tall building.
 Context
 Proportion
c) Tall Building Technologies
If a building contains technologies which may be attributed as being a product of “tall” (e.g., specific vertical transport technologies, structural wind bracing as a product of height, etc.), then this building can be classed as a tall building.
Although number of floors is a poor indicator of defining a tall building due to the changing floor to floor height between differing buildings and functions (e.g., office versus residential usage), a building of perhaps 14 or more stories – or over 50 meters (165 feet) in height – could perhaps be used as a threshold for considering it a “tall building.”
What is a Supertall Building?
The CTBUH defines “supertall” as a building over 300 meters (984 feet) in height. Although great heights are now being achieved with built tall buildings – in excess of 800 meters (2,600 feet) – at the mid-point of 2011 there are only approximately 51 buildings in excess of 300 meters completed and occupied globally.
How is the height of a tall building measured?
The CTBUH recognizes tall building height in three categories:
1. Height to Architectural Top
Height is measured from the level1 of the lowest, significant,2 open-air,3 pedestrian4 entrance to the architectural top of the building, including spires, but not including antennae, signage, flag poles or other functional-technical equipment.5 This measurement is the most widely utilized and is employed to define the Council on Tall Buildings and Urban Habitat rankings of the "World's Tallest Buildings."
2. Highest Occupied Floor
Height is measured from the level1 of the lowest, significant,2 open-air,3 pedestrian4 entrance to the highest occupied6 floor within the building.
3. Height to Tip:
Height is measured from the level1 of the lowest, significant,2 open-air,3 pedestrian4 entrance to the highest point of the building, irrespective of material or function of the highest element (i.e., including antennae, flagpoles, signage and other functional-technical equipment).
Footnotes:
1 Level: finished floor level at threshold of the lowest entrance door.
2 Significant: the entrance should be predominantly above existing or pre-existing grade and permit access to one or more primary uses in the building via elevators, as opposed to ground floor retail or other uses which solely relate/connect to the immediately adjacent external environment. Thus entrances via below-grade sunken plazas or similar are not generally recognized. Also note that access to car park and/or ancillary/support areas are not considered significant entrances.
3 Open-air: the entrance must be located directly off of an external space at that level that is open to air.
4 Pedestrian: refers to common building users or occupants and is intended to exclude service, ancillary, or similar areas.
5 Functional-technical equipment: this is intended to recognize that functional-technical equipment is subject to removal/addition/change as per prevalent technologies, as is often seen in tall buildings (e.g., antennae, signage, wind turbines, etc. are periodically added, shortened, lengthened, removed and/or replaced).
6 Highest occupied floor: this is intended to recognize conditioned space which is designed to be safely and legally occupied by residents, workers or other building users on a consistent basis. It does not include service or mechanical areas which experience occasional maintenance access, etc.
Number of Floors
The number of floors should include the ground floor level and be the number of main floors above ground, including any significant mezzanine floors and major mechanical plant floors. Mechanical mezzanines should not be included if they have a significantly smaller floor area than the major floors below. Similarly, mechanical penthouses or plant rooms protruding above the general roof area should not be counted. Note: CTBUH floor counts may differ from published accounts, as it is common in some regions of the world for certain floor levels not to be included (e.g., the level 4, 14, 24, etc. in Hong Kong).
Building Usage
What is the difference between a tall building and a telecommunications/observation tower?
A tall “building” can be classed as such (as opposed to a telecommunications/observation tower) and is eligible for the "Tallest” lists if at least 50% of its height is occupied by usable floor area.
Single-function and Mixed-use buildings
A single-function tall building is defined as one where 85% or more of its total floor area is dedicated to a single usage.
A mixed-use tall building contains two or more functions (or uses), where each of the functions occupy a significant proportion7 of the tower’s total space. Support areas such as car parks and mechanical plant space do not constitute mixed-use functions. Functions are denoted on CTBUH “Tallest” lists in descending order, e.g., “hotel/office” indicates hotel function above office function.
Footnote:
7This “significant proportion” can be judged as 15% or greater of either: (1) the total floor area, or (2) the total building height, in terms of number of floors occupied for the function. However, care should be taken in the case of supertall towers. For example a 20-story hotel function as part of a 150-story tower does not comply with the 15% rule, though this would clearly constitute mixed-use.
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发表于 2011-7-8 14:10:57
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发表于 2011-7-8 17:11:09