Due to the particularity of super high-rise building structure, beams and columns in the building will inevitably exist. It is difficult to consider the use of special-shaped columns in structural design, especially in the design of super high-rise residential units.
In terms of structural design, according to the design principles of building function requirements, different building heights and economical, reasonable, safe and reliable seismic fortification intensity of the proposed site, the corresponding structural systems are generally divided into six categories: frame structure system, shear wall structure system, frame-shear wall structure system, frame-tube structure system, tube-in-tube structure system and tube-bundle structure system.
Since the 1990s, in addition to the above-mentioned structural systems being widely used, multi-tube structures, frame-tube structures with strengthened stories, conjoined structures, mega-structures, cantilever structures, staggered-floor structures and so on have also been gradually adopted in engineering.
Since 1990s, steel structures and steel-concrete mixed structures have been gradually adopted due to the increase of steel output in China. For example, Jinmao Tower and Wang Di Tower are both steel-concrete mixed structures. In addition, steel reinforced concrete structure and concrete filled steel tube structure are also widely used in high-rise buildings. The strength grade of concrete for high-rise building structure is constantly improving, from C30 to C60 and higher. Prestressed concrete structures are widely used in beam-slab structures of high-rise buildings. The strength grade of steel is also constantly improving.
In the structural design of high-rise and super-high-rise buildings, besides reinforced concrete structure (specification RC), steel reinforced concrete structure (specification SRC), concrete filled steel tube structure (specification CFS) and all-steel structure (specification S or SS) are also adopted.
Building height 100m, column network 8.4m, and seismic fortification intensity of 6 degrees. It is more economical and reasonable to adopt frame-shear wall or frame-core tube structure system. The shear wall or tube of this structural system is a good lateral force resisting member, which often bears most of the horizontal lateral force caused by wind load and earthquake load, and has large overall stiffness and small lateral displacement, which meets the external decoration requirements of glass curtain wall.
The floors and roofs of super high-rise buildings have great plane stiffness, which are the plane lateral force resisting members of vertical steel columns and shear walls or tubes, and at the same time make the steel columns and vertical members (shear walls or tubes) play the role of deformation coordination.
The floors and roofs of steel structures generally adopt rolled profiled steel plates and cast-in-place reinforced concrete (steel bearing concrete for short), and the thickness is generally not less than150 mm. At present, the interaction between steel bearing concrete floors and roofs and steel beams is not considered when designing steel bearing concrete floors and roofs. The main reason is that I don't understand the calculation principle of the wavy bottom of the plate or think the calculation is complicated, so it is unsafe to calculate according to the flat plate, which increases the steel consumption of the steel beam.
If the steel beam and the steel-bearing concrete floor * * * work together, which is called MST composite beam for short, as long as the calculation is correct, the reinforcement is reasonable and the bolts are reliable, the steel consumption of the steel beam on the floor and roof can be saved by about 20%, and it is not necessary to check the stability of the steel beam.
Difficulty 2- Vertical Traffic Design
For super-high-rise buildings, the design of core tube needs to give consideration to lighting, energy saving, easy maintenance, reducing public sharing and unifying core tubes of different formats, which is one of the difficulties in architectural design.
The biggest difference between high-rise buildings and other buildings is that it has a "core", where vertical traffic and pipeline equipment are concentrated and play an important role in the structural system. And this "core" also plays an important role in the form composition, which determines the spatial composition mode of high-rise buildings.
With the development of high-rise building construction, the increase of height and the progress of technology, in the design process of high-rise buildings, the "core" space composition mode of the central core tube has gradually evolved.
1. Inner core type: central core pipe layout
In terms of architectural treatment, in order to strive for the widest possible use space, it is hoped that the service rooms such as elevators, stairs, equipment rooms, toilets and tea stoves will be concentrated in the center of the plane, so that the functional space can occupy the best lighting position and strive for good sight and convenient transportation. In terms of structure, with the emergence of the concept of tube structure and the increase of height, it is also hoped that the tube with stronger stiffness will bear shear and torsion.
In the central part of the building, consciously use the envelope structure of the service building with relatively fixed functions to form a central core tube. The tube is in the geometric center, which can also make the center of mass, stiffness and centroid of the building coincide, which is more conducive to structural stress and earthquake resistance.
After long-term practice, this "core" spatial composition mode has quickly become the most popular spatial layout form in high-rise buildings with its advantages of reasonable structure, convenient use and relatively low cost.
Although the rooms around the central core tube layout need artificial lighting and mechanical ventilation, which will always bring some discomfort to people, the "core" layout form and its variants have an absolute advantage in quantity, and most famous super high-rise office buildings also adopt this form. However, as a super high-rise residential building, this core layout has many inconveniences.
2. Outer core type: double-sided outer core tube layout
With the development of the times, the progress of technology, the change of people's demand for architecture and the different design emphasis, the "core" space composition mode of high-rise buildings with the central core tube as the mainstream has begun to be challenged.
The first change is mainly due to the need of modeling and the change of architectural design concept, such as the "dual-core" composition mode that appeared around the 1970s. The arrangement of bilateral outer core tubes is not only conducive to personnel evacuation, but also greatly changes the appearance of high-rise buildings. I.M. Pei's OCBC Bank Center in Singapore and IBM Benshe Building in Japan are the representatives of the popular bilateral nuclear design methods.
3. Polymorphism: multiple outer nuclei are distributed.
In the second reform, the equipment specialty took the lead in putting forward revolutionary suggestions for the core tube. They think that with more and more construction equipment becoming more and more complicated, it may be more beneficial to management and maintenance if the machine room and pipeline well are separated from the core barrel. Since 1980s, the popularity of intelligent buildings and the increasing number of telecommunication facilities have led to a large number of applications of computers and telecommunication equipment in high-rise buildings. Even after many buildings are completed, the wiring system is often modified and new equipment is added. In the intelligent office building, it is reasonable to set more than three optical cables, computer network management, distribution box and relay equipment on each floor. In this way, in order to meet the needs of frequent changes in mechanical and electrical equipment, the "core" began to disperse, separating several computer rooms and pipeline wells to facilitate local changes.
For the particularity of the structure, strengthening the stiffness around the building will also effectively resist the damage of the earthquake to the high-rise building, so if the vertical traffic and equipment rooms are scattered around, it is undoubtedly beneficial to the earthquake resistance of the structure. At the same time, the spatial composition mode of scattered outer cores is also suitable for the emerging mega-frame structure, which makes the mega-support columns in this structural system have the use function. The most typical example is the "Tokyo Metropolitan Hall" designed by Kenzo Geqin.
From the perspective of architectural design, the movement of the core, vertical traffic, service rooms and tube wells scattered around the building are also revolutionary for the change of the spatial composition mode and facade shape of high-rise buildings. It not only meets the needs of other majors, but also facilitates evacuation, creates more use space and liberates the bottom of high-rise buildings. The flexibility and advancement of this spatial composition mode were quickly discovered by European architects, who highly praised the technical performance and creatively applied it to their works. Lloyd's Building in London designed by Rogers, the office building at No.88 Wood Street and the Hongkong and Shanghai Banking Corporation designed by Foster are all representative works of distributed core tube, which are very different from the high-rise buildings with central core tube in terms of internal space composition and external elevation.
In addition, in small-scale high-rise buildings, in recent years, there has also been a phenomenon that the core is separated from the main use space. Vertical transportation, service building and equipment pipeline are all independent and separated from the main building. The main use space is relatively complete, with all sides facing outward, and there are corridors connecting the core and the main use space. From the structural point of view, the core is relatively rigid, the main body is relatively flexible, and the two parts work separately, which is both reasonable and relatively economical. Of course, the design of connecting part is the key to the design of this kind of high-rise building, but the changes brought by this design method to the architectural appearance have attracted the attention of architects and become popular in Europe and Japan. The management office building of Hanover Architecture Expo in Germany, the office building of Esserwe Company, and the office buildings of Nandajing Building in Northeast Tokyo and Keynes Headquarters in Osaka.
The dispersion and separation of the core and the main use space can also make the stairwell, bathroom and so on direct natural lighting and ventilation, which not only saves energy, but also saves the pressurized air supply equipment needed for fire fighting, which is more in line with the modern design principle of low energy consumption and recycling. Therefore, in recent years, high-rise buildings that emphasize ecological energy conservation often adopt this layout. This high-rise building, designed by Malaysian architect Yang Jingwen, not only has stairs, toilets and so on. They are all exposed, and the elevator pipe wall is specially used to block the sun, which can be described as "an ecological design mode of decentralized outer core space". "Kuala Lumpur Plaza Building" and its newly designed "Singapore Exhibition Building" all reflect this design feature. Another European architect, Herzog, designed the management office building of the above-mentioned Hanover Architecture Expo in Germany, and his ecological concept won public praise.
Difficulty 3- Elevator
Fast, efficient and stable vertical service is one of the difficulties in super high-rise buildings.
As a vertical means of transportation, elevator's quantity configuration, control mode and the selection of related parameters will not only directly affect the one-time investment of buildings (generally elevator investment accounts for about 10% of the total investment of buildings), but also affect the use safety and service quality of buildings. In a building, it is very important to choose the number, capacity, running speed and control mode of elevators reasonably. Once the elevators in the building are selected, installed and used, it is almost a permanent fact, and it is difficult or even impossible to add or modify them in the future. Therefore, we should pay full attention to the elevator configuration at the beginning of design.
Most modern super-high-rise buildings are above 60 stories, and the population in the building flows greatly. Vertical traffic mainly depends on elevators. The key to effectively design elevators in super high-rise buildings is to use all kinds of local elevators to serve and organize elevator systems in local areas. Access to these local areas is provided by the express shuttle elevator between the ground departure station and the air terminal in the local area, and passengers will transfer to the interval elevator after arriving at the air terminal. In order to transport passengers to their destination at the fastest speed, every 30 ~ 35 floors of a building is generally regarded as a local area.
Because the super-high-rise building adopts multi-elevator system, microcomputer elevator control system should be adopted, and a large amount of information can be processed in time by computer control system to judge the call information of each platform, the position, direction, opening and closing state of each elevator and the call in the car, so as to improve the transportation capacity, service quality and economic benefit of the super-high-rise building.
Difficulty 4-Safety and stability of power supply
As a super high-rise building, the design of power supply system must pay special attention to safety, followed by power supply reliability. When designing the distribution system, multi-loop power supply and standby generator set configuration should be considered. Due to the height of super-high buildings, the power distribution room can be set in the middle floor of the tower to reduce the loss of low-voltage power distribution. The standby diesel generator is located in the basement, and the power supply voltage is 10 kV, and then it is reduced to low-voltage distribution through a transformer to ensure power distribution to the top of the tower.
In the power distribution system of super high-rise buildings, the reasonable adjustment of power supply distance, cable length and cable size and the construction technology during installation are also one of the difficult problems. Because of the large area and many floors of super high-rise buildings, the problem of long-distance power supply will naturally occur, so the standby power supply can be considered to generate electricity with high-voltage generators, thus solving this problem.
In addition, we should pay special attention to the fact that super high-rise buildings may swing from side to side when encountering strong winds. Because the super-high-rise building will swing to a certain extent, the cable can be connected to the copper bus duct for power distribution in the design of the ascending trunk line, so as to reduce the pulling pressure of the super-high-rise building on the connecting components of the copper bus duct when swinging, reduce the chances of failure and maintenance, and relatively increase the life of the trunk line system.
After completion, the convenience of the owner must also be considered, and the space layout of electrical equipment should be adjusted. As a super high-rise building with many floors, there are naturally many mechanical and electrical equipment. In order to allow the owner to get more use space, in the arrangement of cables and shafts, the space occupied by changing and shrinking shafts should be reduced as much as possible to provide the owner with more use space.
Difficulty 5- Fire Prevention
Difficulties in fire fighting: Because of its special structural and functional requirements, super high-rise buildings have large internal fire load, rapid fire spread, difficult evacuation and rescue, and there are major fire hazards. For example, in February 2009, a fire broke out in the cultural center attached to the new site of CCTV, causing casualties and property losses.
Key points of fire protection design: fire protection-fire protection-fire resistance
Fire prevention: fire-proof materials, fire-proof components and fire-proof accessories are used in construction projects, non-combustible and flame-retardant building materials are used in decoration projects, ventilation is strengthened in inflammable and explosive places, explosion-proof electricity is set up, and non-combustible ground is used.
Fire fighting: First, control the fire at the initial stage, including installing automatic fire alarm and automatic fire extinguishing system, so as to find and put out the fire early; The second is to control the fire in a small range, divide the fire prevention zone and smoke prevention zone in the plane and vertical direction of the building, and leave an appropriate fire safety distance between the buildings, cut off the fire spread path, reduce the affected area and facilitate the implementation of rescue.
Fire resistance, strengthen the fire stability of building structural members, so that they will not fail in the fire.
Difficulty 6- Measurement
Ultra-high-rise buildings, generally composed of ultra-high-rise towers and multi-storey basements, are difficult to measure. If the construction survey is wrong, the loss will be very serious and it will be difficult to make up and repair. Therefore, engineering survey is the key and difficult point of super high-rise buildings.
Difficulty 7- Influence of crosswind
High-rise and super-high-rise buildings are subject to crosswind. Generally speaking, under normal wind pressure, the height above the ground is 10m, and if the wind speed is 5m/s, the wind speed can reach 15m/s at 90m. If it is as high as 300-400m, the wind will be stronger, that is, when the wind speed reaches more than 30 m/s, the shaking of skyscrapers will be very intense. For this kind of shaking of the building, we should first consider its influence on the elevator, which is regarded as the "lifeline" of the super high-rise building. When the elevator is running at high speed, if the shaking of the building exceeds a certain size, the steel wire rope of the elevator will be damaged due to uneven stress when it is loose, which will cause danger.
Difficulty 8- Stacking Effect
When the temperature is low in winter, the cold air from the lower floors (especially the lobby on the first floor) and the basement rushes into the elevator shaft, forming a strong airflow through stack effect, which makes the elevator unable to close. And it will bring some smells from the bottom up, such as the smell of the kitchen and the smell of oil smoke. At this time, if there is welding operation or gas leakage on the ground floor or basement, the fire source may be brought to the top floor with the airflow, which is extremely dangerous. At the same time, due to the small gap between the elevator car and the shaft wall, when the elevator is running, the friction of airflow will produce howling, which also appears in Jinmao Building. At present, this is an international problem, and no good solution has been found.
Difficulties 9- Management and Maintenance
Some super-high-rise buildings have experienced accidents such as power failure and running water. From the management point of view, it is very important to have a person who knows the overall situation and all the details of the system, in addition to making plans to prevent accidents and making backup systems. The management of Shanghai Jinmao Building once felt very sorry that no one had mastered more than 4000 valves in the building/KLOC-0. Clean glass has also become a problem in managing these behemoths. Jinmao Building Curtain Wall10.180,000 square meters. It is said that two window cleaners can clean all the windows once a year by working continuously. Moreover, due to the uneven shape of the building, there are many overhangs, and in some places there are more than 3 meters, so it is quite difficult to clean the glass.
Difficulty 10- construction difficulty
1. Super high-rise foundation adopts deep foundation. Because the building is tall and bulky, the foundation supporting the high-rise building must reach enough strength, so deep foundation is often used, and the bearing layer is embedded in weathered rock.
2. Super high-rise basement is deep, multi-storey and large in area. First, it is necessary to meet the requirements of building functions, such as the area of civil air defense and the number of parking spaces; The second is to solve the anti-floating problem of the structure during construction.
3. Super high-rise buildings are mostly mixed structures. Such as reinforced concrete, concrete filled steel tubes, reinforced concrete structures or all-steel joints. Their common characteristics are: simple construction, short construction period, good structural performance and great saving of building materials. At present, they have become the most practical main structural forms of super high-rise buildings.
4. Super-high-rise decoration engineering is rich in decoration types, large in engineering quantity, high in technical content and high in requirements. The safety function of super high-rise building decoration engineering is particularly important, which requires high resistance to wind pressure and tightness of wind, water and gas.
5. The building has complex functions, many subsystems, heavy installation workload and high precision.
6. New technologies, new materials and new processes are widely used.
According to the characteristics of super high-rise buildings, the following countermeasures should be taken in construction:
1. There must be a new breakthrough in building technology.
Super-high-rise buildings are not only the superposition of building floors and the extension of buildings, but also must have new elements and breakthroughs in building technology.
(1) deep foundation construction technology. According to geological conditions, large-diameter manual digging pile, punching (drilling) bored pile, precast concrete pipe pile or precast steel pipe pile are generally used for deep foundation, and one or both of them are used at the same time. For the general construction contract, the main consideration is the technical ability, equipment ability, safety and quality control ability of pile construction according to the design. The general contracting project needs to consider the cost factor and the difficulty of obtaining these capabilities.
(2) Earthwork excavation and supporting technology of large foundation pit. According to China's current policy and the needs of the building itself, super-high-rise buildings must have super-large and ultra-deep basement structures, and the biggest difficulty in this part of the project construction lies in earthwork excavation and foundation pit support. Super-high-rise buildings are generally located in the main sections of cities, with narrow space and complex and important surrounding environment. The earthwork excavation plan shall at least solve the following problems:
A. Selection of entrance and excavation route
B. Selection of quantity and performance of earthmoving equipment and layout of entrances and exits
C. Specific measures for final earthwork excavation and transportation
Optimization of foundation pit support technology and deformation monitoring of surrounding buildings and foundation pit slope.
E coordination of earthwork excavation and foundation pit support, even pile foundation construction.
2. The construction organization should have new ideas.
The vertical span of super high-rise buildings is very large, so the construction organization should first solve the problem of vertical transportation efficiency. Solve the huge personnel and material problems with limited mechanical equipment, and achieve orderly and effective.
(1) Rational allocation of large mechanical equipment. It is necessary to calculate the flow of people at the site, how many people need to take the elevator to the site during the peak period of construction, and how long it will take to transport them all. Combined with the time limit for a project plan, calculate and analyze the total consumption and turnover rate requirements of raw materials, turnover materials, finished products and semi-finished products that need to be transported by people and goods elevators, and calculate working hours. On this basis, reasonably determine the specifications, models and quantities of tower cranes and passenger and cargo elevators; Select the performance and quantity of concrete pumps. In fact, buildings with a height of 150m or more should be equipped with a high-speed construction elevator and an ordinary construction elevator to serve different construction areas respectively. A concrete pump shall be selected for pumping, and the oil pump and electric pump shall be fully equipped. The performance and layout of tower crane should not only meet the transportation of steel bars, templates, steel pipes and other materials, but also consider the hoisting and installation needs of steel structure. Carefully plan, be close to reality, and scientifically plan the layout of large machinery. The site conditions and geographical location are analyzed, and the plane layout of large machinery is carried out according to the principle of shortest transportation path and maximum transportation capacity. The transportation route in the floor should be considered first for fast lifting frame and construction elevator; Tower crane should consider the convenience of installation and removal, the coverage area and the feasibility of attaching the wall.
(2) To allocate machinery reasonably, there should be no redundancies, so there will be conflicts in the use of machinery, so it is very necessary to plan the use of machinery. The field operation sequence of each type of work and each working procedure should be arranged in advance and enforced. Reflected in the use of vertical transportation equipment arrangement plan, everyone and everything should know their own transportation time and order. Adjust the use frequency of equipment in a planned and organized way to improve the use efficiency.
(3) Take technical measures to reduce dependence on vertical transportation. The use of steel mesh, mechanical joints and large formwork can effectively improve the labor productivity of field operators and reduce the demand for operators and operating equipment, thus reducing the pressure of vertical transportation.
3. The construction quality requirements are high
In terms of allowable deviation value of total building height, the quality requirements of super high-rise buildings are different from those of ordinary buildings, especially in terms of structural safety performance and building function requirements. Ultra-high-rise buildings bear very large wind pressure, which requires high air tightness and water tightness. Three-dimensional inspection report of glass or curtain wall is essential. In decoration engineering, the construction quality of external wall tile is related to the safety of building use, which must be paid enough attention to and solved from technology and technology. External wall waterproof engineering should be strictly controlled from the aspects of material selection, process test and process quality supervision.
4. Civilized and safe construction management is different from general buildings.
There are many differences between the safety construction management of super-high-rise civilization and ordinary building construction. Three-dimensional crossing construction of decoration engineering and installation engineering. Safety zones and fire zones must be set up. Scaffolding erection and dismantling scheme must be approved, implemented and checked. In addition, large equipment should have safety protection measures and so on. In short, civilized and safe construction should be horizontal to the edge, vertical to the end, measures are in place, and responsibility lies with people.
5. A simple toilet must be set in the floor.
The construction personnel of super high-rise buildings are concentrated, the living quarters and production areas are arranged reasonably, and the daily inspection is effectively controlled.