First, the result of the balance between norms and interests
1 1 floor: there must be a manned elevator above the seventh floor, and there must be a fire elevator above the 1 1 floor, and the fire door must reach Grade B, so it is the building of 1 1 floor that can earn more and spend less (the seventh floor without elevator is mostly the school dormitory floor).
18 floor: emergency exits are required for floors above 1 18, and two exits will be provided for floors above1118, and the stairwell above1/8 should be closed. So it's 18 floor to make money, with less money and less trouble.
26th floor: 19 floor is the first type of fire-proof building (previously it was the second type), the rhythm of two fire-proof elevators (it is also said that there are three elevators and one fire-proof) and two smoke-proof stairs.
Nowadays, many rapidly developing cities will have residential height restrictions, such as 80 meters (airport height restrictions, microwave channels, urban skyline control, urban planning requirements, etc.). 80/3=26 floors, so it is a floor that meets the housing restrictions and maximizes benefits at the same time.
Floor 33: What about those without the above restrictions? What about going up again? According to the General Principles for the Design of Civil Buildings, when the building height exceeds 100m, both residential buildings and public buildings are super high-rise buildings. (More than 40 storeys are required abroad), and 33 storeys 100 meters or more is another standard in terms of specification and safety. Therefore, it is the 33rd floor that makes more money and has less trouble.
B, according to what to determine the number of buildings?
Why is a staircase 1 1 instead of 10 or 12? This is something not mentioned in the specification, but its principle is also very simple. Let me elaborate on it.
There are many sources to determine the demarcation point of building floors. There are requirements for urban planning indicators and environmental impact, and there are requirements for considering human physiological factors, fire protection factors and structural factors.
First, the restrictions of urban planning.
First of all, the building height of a city is controlled by urban planning. For example, if the planning conditions require multi-storey buildings, the dormitory cannot be built to more than seven floors. The planning requires the height to be controlled below 100 meters, so the design will be about 30 floors. If you have a house in the north with a distance of 50 meters, according to the requirements of the southern sunshine distance 1: 1, your height cannot exceed 50 meters, and one meter can cover 16 floors. In the north, if the sunshine interval is 1: 1.2, then only 50/3.11.2 is needed to make up the 13 layer. In addition, now that the land price is high, developers will try their best to strive for higher floor area ratio and saleable area, which also leads to higher and higher housing. From the perspective of economic benefits, the plot ratio index of land is the decisive factor to determine the number of buildings.
Second, people's physiological conditions
This mainly affects the dividing point between multi-storey and high-rise buildings. Multi-storey buildings can be built without elevators. Therefore, considering the physiological limitation of people climbing stairs, elevators should be designed for houses with more than seven floors, and the height of railings should be higher than one meter to ensure safety. There must be an elevator in the office above the seventh floor of the dormitory and above the fifth floor.
Third, the fire facilities factors
This is a condition that has the greatest influence on the critical point of high-rise residential buildings. Simply put, it is the physical strength of firefighters and the height of the ladder truck that determine the common story relationship in residential buildings.
There are two important principles to ensure the fire safety of buildings: one is to ensure the safe evacuation of personnel, which is generally guaranteed by two-way evacuation. So that in case of fire, one end can run out. The second is that fire-fighting facilities can ensure that firefighters put out the fire. In fact, there is another principle, which is to take fire prevention measures to reduce combustible materials and prevent the fire from spreading. But it has little to do with the topic, so I won't go into details.
The fire fighting facilities of the municipal fire brigade rely on fire engines (ladder trucks for rescue) outdoors and fire hydrants indoors. Then the limit of firefighters and fire engines determines the height limit of high-rise buildings. Experiments have been done, and firefighters can climb less than ten floors quickly when they are armed to their teeth, and their physical strength can no longer guarantee to put out the fire immediately. Therefore, the fire elevator should be set after several floors to protect the physical strength of firefighters. However, the height of ordinary fire-fighting ladder truck is limited, so the highest floor of an ordinary elevator+a staircase is also determined, 1 1. Otherwise, the building will catch fire and firefighters can't climb it at all.
The height of an ordinary ladder truck is about 50m (ladder truck _ Baidu Encyclopedia), so it is difficult to directly rescue a building fire above 18 floor (18*3m=54m). This is also required by the fire code. 18 floor is a hurdle. The floors above 18 need to be equipped with smoke-proof stairwells to strictly ensure evacuation safety.
If there is a fire in the middle of a building over 100 meters, it is difficult for people on the upper part to rescue it (not every city has helicopters). Therefore, the code requires that public buildings (about 30 floors) exceeding 100 meters must be provided with refuge floors. Moreover, the height of the first refuge floor should not be higher than 45 meters, which is convenient for fire rescue. /kloc-Houses over 0/00 meters, due to the non-public nature, shall be handled according to local requirements. (generally not)
The above are probably some principles of the number of floors stipulated in the Code for Fire Protection Design of High-rise Civil Buildings. These floors with height conversion are roughly the source of the specific figures asked by the subject.
C elevators and stairwells have a great influence on the interests of all parties.
Unless required by Party A, the designer shall carry out architectural design within the limits permitted by the specification. This advantage is that the cost of Party A is reduced to the greatest extent under the condition of meeting the specifications. After all, people design fees and make more money for others.
The number of floors of residential buildings is often set by the upper limit allowed by the code. This can reduce the building area as much as possible, and correspondingly reduce the excavation area of foundation pit/reduce the number of piles; Expand the greening or square area; Expand the space between buildings; Optimize sunshine conditions and so on.
Of course, dissatisfaction with the floor ceiling also happens from time to time. The reason may be wonderful, because the area was miscalculated before the design, and the designed floor was simply cut off and not built. There are also some conventional reasons, such as unsatisfactory sunshine, planning height limit, geomantic omen, local regulations and so on.
(The above answers were published on 20 16-05-25. Please refer to the actual situation for the current purchase policy. )
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