A Review of Key Technologies Development of Super High-Rise Building Construction in China

Super high-rise building is a typical architectural form of urban modernization, and it is also the trend of urban architectural development. *is paper reviews the development history of super high-rise buildings in China combined with the engineering practice of representative super high-rise buildings since the 1980s, such as the Shanghai Center, Shanghai Oriental Pearl Tower, Jinmao Tower, Shanghai World Financial Center, Canton Tower, and Shanghai Tower. *e development process of the key technologies of super high-rise projects from the aspects of several technologies, such as soft soil pile foundation and foundation pit technology, concrete structure construction technology, integral formwork equipment technology, and steel structure comprehensive installation technology, is also elaborated. At the same time, the Shanghai Tower is selected as a typical case to share the innovative technology of China’s tallest building. Finally, prospects for development of super high-rise construction technology are presented.


Introduction
As a typical architectural form of urban modernization, super high-rise building can effectively realize the architectural function and value increment, which is the trend of urban architectural development. With the invention of the Otis elevator, the mass production of steel, and the advent of reinforced concrete, the bottleneck technology restricting the construction of high-rise and super high buildings has been gradually overcome, and super high buildings have rapidly developed worldwide. Before the 1980s, the world's high-rise and super high buildings were mainly concentrated in developing countries such as the United States, the United Kingdom, Russia, and Canada. After the 1980s, China gradually moved away from the debate about the construction of high-rise and super high buildings. A large number of high-rise and super high buildings were successively built in large cities such as Shanghai, Beijing, and Guangzhou, among which Shanghai is the most representative. Shanghai's representative ultrahigh buildings and structures are mainly concentrated in Lujiazui of the Pudong New District. Combined with the engineering practice of super high buildings such as Shanghai Center, Shanghai Oriental Pearl Tower, Jinmao Tower, Shanghai World Financial Center, Canton Tower, and Shanghai Tower, etc., this paper analyzes and discusses the development of key technologies for ultrahigh construction projects in China by systematically summarizing and reviewing the development history and key construction technologies of representative super high buildings.
Shanghai Peace Hotel was built, and in 1934 the Shanghai Broadway Building (now the Shanghai Building) was built. In the same year, the Shanghai International Hotel, with a height of 83.8 meters and 22 floors above ground, was built by Fu Ji Construction Factory, becoming China's tallest building in the Far East at that time and maintained its position for 34 years.
e Shanghai International Hotel became the zero coordinate point of Shanghai after the liberation, and it is a very famous landmark of high-rise buildings in China [1]. Fu Ji Construction Factory was founded by Tao Guilin  in 1922 and later evolved into the largest construction factory in China. Tao Guilin also became the Chairman of Shanghai and the National Construction Industry Association at that time. e wooden plum blossom piles, steel frames, steam mud brick partition walls, and granite brick walls were used in the Shanghai International Hotel project, of which pile foundation was completed by Kang Yi Yang.

Development of Domestic High-Rise Buildings after
Liberation. After the liberation, the first building in China that surpassed the Shanghai International Hotel was the Guangzhou Hotel built in 1968, with a height of 86.5 meters. Built in 1973, the High Shanghai TV Tower with a height of 210.5 meters became a taller structure than the Shanghai International Hotel. Guangzhou Baiyun Hotel built in 1976 is 120 meters high, which is China's first high-rise building to exceed 100 meters and the first super high building in China. e Shanghai Hotel built in 1981 is 91.5 meters high and is the first building in Shanghai to surpass the Shanghai International Hotel. It can be seen from the development of high-rise buildings during this period that the early urban development after the liberation of China was still at the stage of experience accumulation and development.

Development of Domestic High-Rise Buildings in the 1980s.
In December 1978, China established the policy of reform and opening up. Since then, major cities have been constantly seeking a great leap in development. In the 1980s, Shanghai's high-rise buildings developed rapidly, and Shanghai Construction Engineering completed a number of influential high-rise buildings. Shanghai Center, Shanghai New Jinjiang Hotel, Shanghai Hilton Hotel, Shanghai Garden Hotel, Shanghai Hailun Hotel, etc. were the most famous super high buildings in Shanghai in the 1980s. Among them, Shanghai Center, which was built in 1989, was the largest and tallest super high building in Shanghai at that time. It was built in accordance with international practices introduced by foreign capital after China's reform and opening up. In 1987, Premier Li Peng proposed to promote the "Lubuge Experience" at the National Construction Work Conference of the State Council. Lubuge was a hydropower station project in China at that time. As bidding must be adopted for the loans from the World Bank, China has learned the world's advanced legal practices for construction projects while introducing foreign investment [2]. Shanghai Center was also a construction project that introduced foreign investment at this stage, so project management method was also introduced. It was the first project to adopt the concept of project management in domestic construction projects, which had a profound impact on the field of engineering construction in China at that time. e method has been continuously developed and implemented to this day.

Construction of Lujiazui during Opening Up and
Development of Shanghai Pudong. In April 1990, Shanghai Pudong was developed and opened up, and the Lujiazui area developed rapidly. In the 1980s, Pudong and Puxi in Shanghai, located across the river and facing each other, developed very differently. At this time, there was a saying that "I would rather have a bed in Puxi than a building in Pudong." Before the 1990s, there was no bridge over the Huangpu River in Shanghai, only the Dapu Road tunnel for wars. Pudong was dominated by crowded low-rise residential houses. In the early days of Pudong's development and opening up, people used ferry to get to and from work every day, which is totally different from the current traffic of many bridges and tunnels.
is also reflects the tremendous changes in Shanghai's urban construction in more than 30 years of Pudong's development and opening up. e development of ultrahigh buildings in the Lujiazui area of Pudong, Shanghai, represents that of super high buildings in China.

Development of Domestic High-Rise Buildings in the 1990s.
Since the 1990s, Shanghai Construction Engineering has successively undertaken the construction of the tallest buildings and structures in different periods. e construction technology of tall structures has been continuously improved. e comprehensive construction capacity has reached the international advanced level, some of which has even reached the international leading level. e Shanghai Oriental Pearl Tower, the tallest structure in China in the 1990s, was completed in 1994 and reached a height of 468 meters, becoming the tallest building in China and the third tallest in the world [3]. It was a milestone project in the development of China's structure construction technology. e Shanghai Oriental Pearl Tower Project was very difficult to construct at that time, because before that the tallest building in Shanghai was the 168-meter Shanghai Center, and the construction height exceeded 300 meters, which made it impossible for many technologies to meet the needs of the time. erefore, at this stage, a large number of new technologies developed by innovation were applied [4]. In 1996, the project of "Research and Application of Construction Technology and Equipment of Shanghai Radio and TV Tower" won the second prize of National Science and Technology Progress Award of China.
e Jinmao Tower, the tallest building in China in the 1990s, is 420.5 meters high. Completed in 1998, it was the first ultrahigh building in China with a height of more than 400 meters [5,6]. When completed, it was the first tallest building in China and the third tallest in the world. It was also a milestone project in the development of construction technology in China. A hybrid structure system of concrete structure and steel structure was adopted in the project. Such ultrahigh structure system was the first to be adopted in China at that time, and many new technologies were innovatively adopted in the process of engineering construction. In 1999, the project of "Research on Construction Technology of Super High-Rise Buildings-Jinmao Tower 88" won the first prize of National Science and Technology Progress Award of China.
Starting at the beginning of the 21st century and completed in 2008, the Shanghai World Financial Center with a height of 492 meters is the tallest ultrahigh building in China, becoming the tallest building in China at that time and the third tallest building in the world. is project has achieved a breakthrough especially in the scale application of the third generation of polycarboxylic acid system admixtures in concrete [7]. In 2012, the project of "Key Technologies of Shanghai World Financial Center Engineering Construction" won the second prize of National Science and Technology Progress Award of China. e tallest structure in China is the Canton Tower. It was the first ultrahigh structure in China, with a height of 610 meters. When completed in 2009, it was the tallest tower in the world, but now it is the tallest tower in China and the second tallest in the world [8]. e structure of the Canton Tower Project is complex and changeable. e outer grid is composed of 24 inclined steel-pipe concrete columns with a maximum diameter of 2 meters. e tower is characterized by ultrahigh, torsion, eccentric, air-permeable, and slim-waisted structure [9]. In 2016, the "Key Technologies of Canton Tower Project" won the second prize of National Science and Technology Progress Award of China. e tallest building in China is the Shanghai Tower, which has a height of 632 meters and was completed in 2015. It is the first super high building in China to exceed 600 meters in height [10][11][12]. It is now the first tallest building in China and the second tallest in the world. is project has been awarded three-star certification of the highest level of green building in China and the LEED-CS platinum certification of the highest level of green building in the United States. A double-layer curtain wall system is adopted, and a curved building exterior with 120°torsion and 55% upward split is innovatively designed. In 2018, the research achievement of "Key Technology of Shanghai Tower Project" won the Shanghai Science and Technology Progress Special Award of China. e above-mentioned projects are influential not only in China, but also in the world. Jinmao Tower, Shanghai Tower, and Shanghai World Financial Center, the three tallest buildings in China in different periods in recent times, were awarded "50 Most Influential Tall  Nowadays, China's high-rise building construction has made a very significant development [1]. At present, there are three super high buildings over 600 meters in the world, with one in China; 10 super high buildings over 500 meters, with 4 in mainland China; 34 super high buildings over 400 meters, with 14 in mainland China; 185 super high buildings over 300 meters in the world, with 85 in mainland China; and 1,688 super high buildings over 200 meters in the world, with 708 in mainland China. From these data, we can see that China's super high buildings have exceeded 40% of the world's total. Now, China has been worthy of being a superpower of super high construction projects, which is attributed to the rapid development of urban construction since China's reform and opening up.
According to Table 1, as of June 2021, six of the world's top ten super high-rise buildings are in mainland China, and according to Table 2, four of the world's ten tallest structures are in China.

Soft Soil Pile Foundation and Foundation
Pit Project

Technology of Soft Soil Foundation Pile.
Before the liberation, there were a small number of high-rise buildings in Shanghai, and pile foundation of supporting buildings Advances in Civil Engineering usually adopted driven-in wooden piles, with poor ability of wooden piles to control settlement. In the early days after the liberation, with the increase of project scale, pile foundation was mainly on-site precast concrete square piles, and it was highly applied in Shanghai Oriental Pearl Tower. e precast concrete square piles were 48 m in length, with a cross section of 500 × 500 mm. ree-section piles and steel plate were connected, and bearing capacity of pile foundation was designed with 450 t. As construction projects become higher, the load is getting bigger and bigger, and accordingly more requirements are proposed for bearing capacity of pile foundation. However, precast concrete square piles fail to meet the requirements, so the steel-pipe pile technology is developed by Shanghai Jinmao Tower and Shanghai World Financial Center. To be specific, in Shanghai Jinmao Tower Project, steel-pipe piles are used with a diameter of 91.4 cm and pile depth of 83 m. e lengths of the first, second, and third piles are 25 m, 23 m, and 17 m, respectively. When the pile is sent to the ninth layer of silty-fine sand, the design bearing capacity of a single pile reaches 1,500 t [13]. In terms of Shanghai World Financial Center project, steel-pipe piles with a diameter of 70 cm are adopted. e pile depth is 79 m in the middle; at the edge, long and short piles whose depth is 60 m are arranged. e design bearing capacity of a single pile is 750 t. Strictly speaking, steel-pipe piles are suitable for super high-rise buildings with large loads, and quality of construction process can be guaranteed easily [14]. When Shanghai Tower was being constructed, there was Lujiazui area surrounding the construction area, and it had become a dense urban area where construction of high-noise drive-in pile foundation projects was forbidden. erefore, only concrete bored piles were suitable in soft soil foundations at that time. However, one difficulty was about how to improve bearing capacity of such piles. In order to verify feasibility of concrete bored piles, the researcher conducted a systematic in situ test and researched on the spot. rough technological innovation and process improvement, it was proved that concrete bored piles for soft soil foundations could meet bearing capacity requirements of Shanghai Tower. is project breaks through the tradition of steel-pipe pile technology for soft soil foundations because concrete bored piles are firstly adopted in super high rises above 350 m. e pile length is 86 m, and bottom of piles is sent to the ninth soil layer of silty-fine sand, a typical supporting layer in Shanghai. After piles are formed, the pile-tip grouting process is used to control grouting amount and grouting pressure, improving ultimate bearing capacity of pile foundation by nearly 4 times. e ultimate bearing capacity of pile foundation in test is 2,500 t～3,000 t, and the design bearing capacity of a single pile is 1,000 t. erefore, Shanghai Tower of 850,000 tons is supported firmly by 955 piles in main building. e bored pile technology applies bentonite mud to protect walls, degritting technology in mud, positive cycle construction technology in shallow soft soil, and back-cycling construction technology in hard strata of deep sand. With respect to verticality control of pile foundation, a complete set of construction technologies are developed innovatively, which improves vertical accuracy of pore-forming by more than 50% compared with the national standard. e innovative construction technology of bored piles has served as a reference for subsequent constructors to apply bored piles in super high-rise buildings on soft foundations in China. According to the research results, concrete bored piles can fully meet construction needs of   [15]. e development of soft soil pile foundation technology has laid the foundation for the construction of super high-rise buildings of 800 m and even higher.

Technology of Soft Soil Foundation
Pit. Diaphragm wall is the major form of super large and deep foundation pit projects in soft soil. After long-term development, the construction technology of diaphragm wall has evolved from traditional technology of grabbing soil for grooving into the combination of grabbing and milling to create a groove. At present, the new construction technology of casing milling for grooving has experienced sound development.
e diaphragm wall of Shanghai Jinmao Tower is 36 m in depth and 1 m in thickness. It combines technology of grabbing soil for grooving and "two drills and one digging", with the former technology being suitable for soft soils and latter for pan soil, and it is relatively difficult to form a trough in pan soil [16]. e diaphragm wall of Shanghai Tower is 50 m in depth and 1.2 m in thickness. It adopts grabbing soil for grooving and casing milling for grooving in soft soil layer and hardpan, respectively. e grooving in hardpan process is mature, and the construction depth of diaphragm wall has been increased significantly. In addition, casing milling for grooving is practiced in Shanghai Tower Project, which is the first time for Chinese projects to adopt OCJ technology for soft soil foundations. Breakthroughs have been made in construction depth of diaphragm wall [17,18]. At present, Shanghai soft soil foundation has successfully completed construction verification test of 150 m ultradeep diaphragm wall, and the actual application depth of the project is 105 m, setting a new record for construction depth of domestic construction projects. e casing milling for grooving of diaphragm wall adopts jointless box process, which perfectly solves possible turbulence control problem caused by concrete pouring of the ultradeep diaphragm wall and abandons the technical bottleneck that traditional joint box is easy to pull off in construction of ultradeep diaphragm wall.
In soft soil foundation projects in Shanghai, with continuous expansion of scale of super high-rise building foundation pits, it is common to see foundation pits with a single-story area of over 20,000 m 2 and a depth of more than 20 m. It is difficult for the traditional construction methods such as single normal construction method and single reversed construction method to meet the optimal control goals of construction period, cost, and environmental protection. erefore, combination of foundation pit support technologies is popular [19]. In particular, projects where foundation pit divisions are separated apply combination of normal construction method, and combination of normal construction method and reversed construction method. If there is no separation, the combination of normal construction method and reversed construction method, and the combination of reversed construction method for beams and normal construction method for slab develop fast as foundation pit support technologies. A large number of projects have become classic cases of foundation pit construction in soft soil.
Here is the case of construction of foundation pit of Shanghai Jinmao Tower. Support technology of combining normal construction method is adopted in separated zones of foundation pit. e single-layer area of the foundation pit is 20,000 m 2 , and the depth is 19.65 m. Due to control of dominated construction period of main building, support method by zones is adopted in the main building and the podium, which means the main building will be constructed first, followed by podium. e construction of foundation pit abandoned traditional construction concept at that time.
e support system was designed as an integral of excavator platform, parking platform, and vehicle trestle in the construction process, dramatically improving construction efficiency and ensuring safe construction of foundation pit.
is is an innovation and is widely adopted in the subsequent construction of deep and large foundation pits.
In construction project of foundation pit of Shanghai Tower, the support technology combining normal construction method and reversed construction method suitable for division is applied. e single-layer area of foundation pit is 30,000 m 2 , and the depth is 33.1 m. In main building area, normal construction method applicable to partition of circular diaphragm wall enclosure is adopted, and partitioned reversed construction method is used in podiums [20]. At the same time, there is a 121 m large-diameter circular self-standing diaphragm wall enclosure structure in main building area, and it is constructed firstly, aiming to minimize construction period of the main building to the largest extent. is is the self-standing enclosure structure with the largest diameter on soft soil foundation, but construction difficulty is how to guarantee roundness of self-standing circular support structure. e control of roundness is the key to success or failure. In podium area, replacement of floor slab with support is another reversed construction method, which can greatly save project cost provided that construction period is not dominated. In successive construction process of the floor slab around the podium, basin-type earth excavation construction method of "cross" slab symmetry first is used, to effectively control deformation of the surrounding environment of the foundation pit [21].
For example, Shanghai Xinzhuang Longzhimeng Foundation Pit Project adopted reversed construction method and normal construction method in the pit zone without partition walls. e single-layer area of foundation pit is 27,000 m 2 , and the depth is 20 m. e main method is reversed construction method of stepping ring plate structure at the side of foundation pit, but in middle structure, normal construction method is applied according to partitions. Furthermore, an oblique ramp for earthmoving vehicles to enter foundation pit is set in light of ring plate structure, so as to meet highly efficient earth excavation. Another example is foundation pit of Shanghai Lujiazui Financial Center Building, where the technical method of replacing temporary supports with structural beams is introduced.
e main process is that reversed construction method is resorted to for replacing supports with frame Advances in Civil Engineering beams. Besides, frame superimposed slab structure is constructed in accordance with normal construction method, and so is the main building area.
With the progress of foundation pit project construction technology, micro-deformation control of environment has become a new difficulty in controlling foundation pit. e construction of deep and large foundation pits in central urban area not only aims to meet needs of construction main basement, but also is particularly important for deformation control of adjacent underground lifelines and ground protection buildings. Deformation control of adjacent protection objects is a new research perspective of foundation pit projects. In recent years, Shanghai Construction Group (SCG), Tongji Architectural Design, and other companies have conducted extensive research and project practices related to the micro-deformation control technology of construction environment of deep and large foundation pits. In terms of the technical problem that environmental disturbance control around enclosure cannot be solved by reducing deformation of the enclosure, an analysis method that helps explore depth of impact of unloading rebound in soft soil foundation pit and the displacement field of deep slip band bypassing bottom of enclosure is proposed. Influence mechanism of environmental disturbance around large and small foundation pits was revealed. Divisional support and divisional unloading enclosure of the foundation pit and its micro-deformation control technologies of surrounding environment were established, which provides technical methods for design and construction of foundation pit with strict micro-deformation control in the soft soil area of Shanghai. Based on deformation control mechanism of deep slip band, design technologies are established for small partitions of super large foundation pit far away from the protection objects and short divisions of super long foundation pit close to the protection objects. For the construction of large foundation pit at the far end of protection objects, a symmetrical, balanced, and blocktime-limited excavation mode for the deformation control of the soft soil rheological properties is constructed. As for construction of narrow and small foundation pit near the protection objects, deformation of foundation pit is intelligently controlled through coordinated use of steel support axial force servo system. Various micro-deformation control technologies can be applied comprehensively to control deformation of protection objects at millimeter level. Technical methods for deformation control of foundation pit earth excavation enclosure on rheological properties of soft soil could be found in Chapter 23, Construction of Foundation Pit Earthwork, in Handbook of Foundation Pit Project [22].

Concrete Construction Technology in the 1980s.
In the 1980s, self-mixing concrete has been adopted in most concrete projects. In 1980, the Japanese equipment was introduced in the Shanghai Baosteel Project, and the construction technology of commercial concrete with wood calcium admixtures and fly ash was developed. e 7,100 m large-volume foundation slab pouring has been completed at Baosteel Project by Shanghai Construction Group. Since then, the research on crack control technology for mass concrete pouring has been carried out. In 1985, the number 300 and number 350 strength grade concrete have been fully adopted in Shanghai Center. e total volume of the foundation mass concrete reached 5,500 m , and the thickness reached 2.25 meters. In order to solve the problem of concrete crack control, a layered pouring method was adopted. e first layer of concrete was poured. e thickness is 1.2 meters. e second layer of concrete is constructed after the curing is completed. e thickness of the second layer of concrete is 1.05 meters. e layered pouring to reduce the volume becomes a method of concrete crack control. In 1986, in the Shanghai Hailun Hotel project built by Shanghai Construction Engineering, the foundation concrete number was 300, and the concrete volume reached 8,700 m . During the process of construction, the concrete was poured at one time, and the mass concrete cracks were controlled at one time, setting a new domestic record. e concrete transportation height of the Shanghai Center physical structure reached 168 meters at one time, setting a new domestic height record for the performance control of the concrete transportation at one time [1].

Concrete Construction Technology in the 1990s.
In the 1990s, the second-generation naphthalene-based admixture single-mixed fly ash concrete construction technology was mainly developed. e Shanghai Oriental Pearl TV Tower has been under construction since 1990. e number 400 strength grade concrete was adopted, and the maximum pumping height of the solid structure concrete was 350 meters at one time. e Jinmao Tower Project construction started in 1994, and C50 and C60 strength grade concrete were used, of which the construction technology reached a higher level. e base slab concrete of the main building of Jinmao Tower is 4 meters thick with a square volume of 13,500 m . e C50R56 strength grade and age-required concrete has been adopted. e positive and negative circulation balanced cooling water pipe cooling system became an effective method for mass concrete temperature control within 100°C. Furthermore, the highest internal temperature rise of the Jinmao Tower base concrete was 96°C. e maximum C40 strength grade concrete pumping height at one time for Jinmao Tower Project solid structure reached 382.5 meters, which created a new domestic and foreign record of the maximum pumping height of the solid structure concrete at one time [24].

Concrete Construction Technology since the 21st Century.
In 2005, the third-generation polycarboxylate-based admixture with fly ash and slag double-mixing concrete construction technology have been fully adopted in the Shanghai World Financial Center, with C50 and C60 strength grade concrete. Self-compacting concrete succeeded in scale application for the first time in super highrise buildings, and concrete performance indicators have been comprehensively improved. e bottom plate concrete of the main building of Shanghai World Financial Center is 4.5 meters thick, with a square volume of 28,900 m . C40R60 strength grade and age-required concrete was adopted. Due to the double-mixing concrete technology, cement consumption was substantially decreased. e temperature rise of the concrete is controlled without the need for water pipe cooling system. e maximum temperature rising inside the mass concrete pouring is only 68°C, which created a new record for the control of cracks for the one-time continuous pouring of large-volume concrete in domestic and foreign construction projects at that time [7,25]. e maximum C60 and C40 strength grade concrete pumping height at one time for solid structure reached 290 and 492 meters, respectively, which have created a new domestic record. In 2010, the foundation slab concrete of the main building of the Shanghai Tower was 6 meters thick and 121 meters long, with a total volume of 60,000 m , using C50R90 strength grade and age-required concrete, with the internal temperature rise of the concrete is up to 71°C [26]. High performance mineral admixtures and high efficiency admixture were used together to reduce the hydration heat, which reduced the cracking risk of mass concrete in the project of the Shanghai Tower. In 2014, the one-time pumping height of C35 strength grade concrete in the Shanghai Tower Project was 607.8 meters, and 120 MPa concrete was pumped to the height of 620 meters at one time as a proof experiment. e Shanghai Tower has created a new record at home and abroad for the control of cracks in one-time continuous pouring of mass concrete in construction projects [27]. It has created a new record at home and abroad for the pumping height at one time for solid structure, surpassing the 601-meter height record of the world's tallest building, Burj Khalifa [28,29].
A breakthrough has been made in the crack control technology of large-volume, high-strength, low-hydrationheat, and low-shrinkage concrete, and the control of the onetime pumping height and performance control of concrete has also continuously broken new records. e unit cement consumption of concrete can be reduced by more than 50%, the adiabatic temperature rising can be reduced by above 12°C, the 180-day shrinkage value of concrete can be reduced by more than 50%, and the comprehensive application of new technologies can reduce the conveying resistance by more than 50%. Judging from these index data, concrete construction technology has been achieved with all-round development [30].

Concrete Construction Technology
System. In recent years, Shanghai Construction Group has made remarkable achievements not only in concrete engineering practice but also in theoretical research. In terms of mass concrete construction, the law of temperature difference evolution during concrete construction process was revealed, and temperature control technology based on temperature gradient concept was established on research and engineering practice. In super high conveying concrete construction, a discrete element analysis of coordinated control of comprehensive performance indicators and the control technology of rheological parameters were established. In the aspect of vertical deformation control of super high-rise construction, the technology of vertical deformation modeling analysis, process evaluation, and construction control of super high-rise structure have been established, and the elevation classification of different sections of super high structure construction with compensation precontrol method has been established. e development of concrete construction technology for more than 20 years has been summarized. e cast-in-place structural engineering and the corresponding acceptance content have been adopted by the national standard system. On the basis of technical research and engineering practice, the provisions of the construction control technical methods for concrete pouring of different structures have been formulated, which are included in the "Cast-In-Situ Concrete" chapter of the newly compiled national standard "Construction Specification for Concrete Structures," GB50666-2011 [31]. Quality control has been formulated and revised in standard provisions. For example, the verticality control standard for super high-rise buildings is included in the revised national standard "Quality Acceptance Specification for Concrete Structure Engineering Construction", GB50204-2015, "Cast Structure" chapter; a new national standard provision system for "Cast Part" has been established [32].

Development History of Integral Formwork Technology.
Integral formwork equipment has now become very important equipment for China's super high-rise construction. In 1992, the Oriental Pearl TV Tower has pioneered the use of the integral steel platform formwork technology based on the inner tube and outer frame technology. en, the integral steel platform formwork technology based on the temporary steel column technology, the rigid steel column technology, the steel beam tube frame technology, and the steel column tube frame technology have been invented in the construction of major projects, of which five different types of integral formwork equipment technologies have laid the foundation for the construction of China's ultrahigh engineering. In recent years, these technology systems have been adopted in the tallest buildings and tallest structures in different periods in China [33].

Development of Traditional Integral Formwork
Technology. Aiming at solving the technical problems of traditional climbing formwork process bearing capacity, three-dimensional protection, and construction efficiency, the integral formwork technology of inner cylinder and outer frame supporting climbing was created in 1992, forming an integral mobile fully enclosed safety protection Advances in Civil Engineering operation system. e technology has been applied to the Shanghai Oriental Pearl TV Tower Project for the first time. In 1996, the integral formwork technology of temporary steel column support for climbing, innovative wall top bearing method, support and climbing system integration technology were invented, which solved the problem of heavy-load and large-span construction. e integral formwork equipment technology of temporary steel column was applied in the Jinmao Tower and the World Financial Center Project [34,35]. As to the Canton Tower Project, since 14 steel stiffened steel columns were set in the concrete core wall, the stiff steel columns have been used instead of temporary steel columns as supporting climbing tools. e integral formwork technology of rigid steel column support for climbing has been innovatively formed [36]. After 2007, the overall formwork equipment technology method has been adopted in a large number of projects including Guangzhou West Tower and Guangzhou East Tower. So far, the overall formwork technology concept has been widely adopted in the industry.

Development of Integral Formwork with Intelligent Control Technology.
e traditional monolithic steel platform formwork technology solves the technical problems of low bearing capacity of the frame, low construction efficiency, and imperfect three-dimensional safety protection, but technical problems such as the diversified power drive, standard modular integration, intelligent operation control, and special structural layer adaptation have not been solved yet. e national "Twelfth Five-Year" science and technology support plan project undertaken by Shanghai Construction Group "Research and Demonstration of Formwork and Transfer Pump Equipment for ousand-Meter Super High-Rise Construction of Integrated Steel Platforms" (2014BAJ03B00) and the national " irteenth Five-Year" key research and development plan project "Development of Key Technologies for Integrated Platform and Equipment for Industrialized Construction On-Site" (2018YFC0705800) carried out system research and engineering practice, and the integral formwork equipment technology with intelligent control has been developed. Aiming at solving the technical problem of the high-quality development of the integral formwork equipment, the intelligent controlling integral formwork equipment technology with bottom-mounted jacking type and the intelligent controlling integral formwork equipment technology with upper-mounted lifting type were invented. e hydraulic power system can be set at the lower part or the upper part of the steel platform according to the engineering needs, and the adaptability of special structure construction is significantly improved, of which two intelligent controlling construction methods have become a new type of integral formwork equipment technology with intelligent control [37,38].
In terms of intelligent control and standardized design, the new integral formwork equipment technology realizes the intelligent control of the whole process of climbing operations, and the construction of the digital standard modular series product library has been completed. e equipment turnover rate can reach more than 90%, and the industrialized construction technology of modular integration has been fully embodied. e digital design and virtual simulation construction has been realized through the developed platform system. e on-site construction process could be digitally and intelligently controlled [39].
In view of the difficulty of the construction of the integral steel platform formwork in the special structure layer, the hydraulic power drive control of the scaffold integral displacement technology was developed to solve the construction problems of the structure splitting and the body shape conversion. e rigid steel plate with the double-layer operation mode was developed, and the construction problem of the shear steel plate layer installation has been solved by the fixed-point in-place sliding installation technology.
e installation technology of the flexible deformation conversion of the steel platform and the scaffold has been developed to solve the construction problem of the outrigger truss layer. e new integral formwork equipment technology has changed the construction difficulty of the special structure layer of the traditional integral formwork system, so the construction efficiency is greatly improved, and the construction risk is greatly reduced [40,41]. e integration of integral steel platform formwork equipment and construction machinery is also a fast-developing technical aspect. In order to reduce the intensity of construction work, improve the level of integrated construction technology, and solve the problem of large-scale construction machinery attaching to the structure and the efficiency of climbing construction work, integrated formwork equipment with hoisting tower cranes, passenger and cargo elevators, and concrete placing machines technology has been developed and established. e integration of the integral steel platform formwork equipment and the hoisting tower crane is relatively complicated. e developed integrated connection control device can realize the efficient separation and switching between each other, and the efficient climbing and operating of the integral formwork equipment attached to the hoisting tower crane have been completed. e use of the non-bolting, non-welding high efficiency contact support technology; the traditional connection method of the lifting tower crane; and the main structure has been completely abandoned, greatly improving the construction efficiency. e integration of the integral steel platform formwork equipment and the people-cargo elevator is mainly realized by the way of sliding connection attached to the wall without separation from each other, which solves the technical problem of the people-cargo elevator directly rising to the top of the overall steel platform for efficient transportation [42]. e main method for the integration of the integral steel platform formwork equipment and the concrete spreader is to set the concrete spreader directly on the top of the integral steel platform, and it is realized by a fixed method of efficient assembly and disassembly connection or a track-type connection method. e integrated technology application of integral formwork equipment and mechanical equipment with a load of more than 2,000 t has formed a new efficient construction mode. 8 Advances in Civil Engineering

eoretical Basis and Standard System.
e theoretical basis and standard system of the integral formwork equipment structure analysis, design calculations, construction methods, and construction control have been established based on engineering practice, experimental research, and theoretical research. e hysteresis test research is mainly carried out for the key components and nodes of the integral formwork, and the design is optimized through experiments to provide a basis for the selection of the calculation model parameters.
e wind tunnel test provided evidence for the formulation of the wind load design value and the construction control limit of the integral formwork equipment [43]. Summarizing the development achievements of integral formwork equipment technology in more than 30 years, the first national integral formwork industry standard "Integral Climbing Steel Platform Formwork Technical Standards", JGJ459-2019, has been edited [44]; the terminology system has been unified; the structural analysis has been established; and the design calculation standards, standardized structural requirements, and work safety regulations have been formulated. e first published book "Ultrahigh Structure Construction of Integral Steel Platform Formwork Equipment Technology" systematically discussed the integral formwork technology, established the theoretical basis of the integral formwork, constructed the integral formwork technology system, and discussed the engineering application methods in detail. e industrialized application of the established major equipment has laid the foundation. e major equipment technology of the integral formwork won the second prize of the National Technical Invention of China. e integral formwork technology has been industrialized in hundreds of projects in more than 20 cities. e integral formwork technology of the Jinmao Tower Project has created the speed of building a one-story structure in China in two days. e overall turnover rate of the integral formwork equipment that can actually be achieved is more than 90%.

Installation Technology of Mast Integral Lifting.
A mast is usually set on the top of a super high TV tower project, and the installation of the mast is also a key technology for the construction of a super high structure. e mast of Shanghai Oriental Pearl TV Tower weighs 450 t, and the mast height is 118 meters. e integral lifting technology of steel strand is adopted without counterweight hydraulic jack. e space is reserved in the middle of the tower, and the mast is transported to the bottom of the tower for connection. Lifting installation was done after the connection was formed as a whole, and the top mast was connected to the top of the tower structure after being out of the barrel [45]. e total height of the mast of the Canton Tower Project is 150 meters, the height of the lifting section is 90 meters, and the lifting section weighs 630 tons. e integral lifting technology of steel strands without counterweight hydraulic jacks is also used. e mast part outside the lifting section is hoisted. e tower crane is installed and connected in sections, and then the mast part that has been installed first is used as the cylinder to set the jack steel strands. e lifting section is connected in sections by the tower crane to form a whole, and finally the whole is lifted and installed in place [46]. For the connection between the mast and structure of the Canton Tower Project, a detachable anchoring method is adopted, which is convenient for the height reduction of the mast during use. e height of the Canton Tower mast was initially 610 meters, and after completion, it was lowered by 10 meters according to relevant requirements. Now, the current height of the Canton Tower is 600 meters.

Installation Technology of Complex Steel Structure.
In terms of super high-rise buildings, Jinmao Tower is the first building in China to exceed 400 meters in height. In response to the problems of compression deformation, shrinkage and creep of super high steel-concrete structures, and vertical deformation and control of stack drop, the precontrol method of elevation compensation in different section has been adopted. e set of technical methods for controlling floor elevation is the first to be developed and applied in engineering practice in China. e main member bars of the outer steel frame project in the main structure of Jinmao Tower are connected by bolts, and the main connection nodes are connected by pin shafts. e accuracy control requirement is within 2 mm. e rigid steel structure of the giant column is processed in sections. e steel structure of the giant column is hoisted first, and then the frame beam structure is hoisted. e outrigger truss is preassembled in the factory. en, it is hoisted on site. e outrigger truss is first articulated and connected in the structure construction. After the top is deformed and stabilized, the final fixed connection is carried out. e total weight of the spire is 40.7 t, and the total length is 50.4 meters.
e technical method of double tower crane has been adopted when it is installed. e steel structure installation project of Jinmao Tower has become a typical project of full bolt connection [47]. e main member bars of the outer steel frame project in the main structure of the Shanghai World Financial Center are all connected by welding, and the steel structure system of giant columns, giant diagonal braces, ribbon trusses, composite floor slabs, and outrigger truss has been further developed [1]. e outer steel frame part was hoisted in advance with the huge four-corner rigidity column. A stable steel structure system with the four-corner rigidity has been formed by the connection between the floor frame beam and the core tube, and then the four-corner large rigidity and stable steel structure were used to extend to each side to continue installing the frame beam steel structure. Horizontal beams and columns on each level are used in the giant diagonal brace for stable installation and connection. e form of local articulation has been adopted in the installation of outrigger truss, and the welded final connection is carried out after the deformation is stable on both sides. e steel structure installation project of Shanghai World Financial Center has become a classic project of all-welded connection.
Advances in Civil Engineering e structural system of the outer steel frame project in the main structure of the Canton Tower is very complicated, and its super high, eccentric, torsion, slim-waisted, airpermeable, and flexible structural features make installation difficult. As the steel structure is a large eccentric 10 m structural system, the integrated method of construction monitoring control, operation, and maintenance sharing has been adopted in the installation and displacement control of steel structure, which realizes high-precision installation of steel structure. In order to solve the deformation control problem of the key connection nodes of the steel structure, an in-line radial joint bearing universal hinge adapted to the torsional deformation of the outer cylinder steel structure was innovatively developed to achieve the coordination of in-plane deformation and torsional deformation. e universal hinge connection method is the first successfully applied one. e design method of staggered and obliquely crossed outer tube nodes has been adopted in the key connection node of the steel structure, which fully reflects the visual aesthetic effect of the building. In response to the predeformation control problem, a new structural predeformation control technology of segment adjustment and ring-by-ring resetting was developed to form the segment outer frame steel structure column, diagonal brace plane, ring beam predeformation, and stage vertical predeformation control technology. In order to solve the problem of safety protection for suspended operations, a safety protection system integrating satellite operating platforms, radial channels, and multiple isolations for suspended operations has been developed to achieve efficient and safe construction [46]. e Shanghai Tower is designed with a double-skin glass curtain wall system, and an integrated structural system of internal rigidity and external flexibility has been adopted in the structure. e internal structural system is similar to the traditional steel-concrete structure [10]. A flexible suspension structural system has been adopted in the external structural system, and the external flexible suspension structure is connected to the internal rigid structural system. 4 M1280D tower cranes have been adopted in the installation of steel structure. In order to improve the ergonomics, the weight of the steel structure section unit is controlled within 100 tons, and 2 M1280D tower cranes are adopted in the super large components for dual crane installation. e difficulty in the steel structure engineering of the Shanghai Tower lies in the precontrol installation technology for the deformation of the outer flexible steel structure. How to solve the deformation control of the flexible suspension system based on various loads, vertical deformation, temperature effects, etc. has become an engineering problem. e restraint release in the internal rigid and external flexible structure connection and the deformation absorption double-layer structure construction control technology method have been innovatively developed based on systematic research and analysis of a large amount of calculation data. e development of five types of flexible connection sliding bearing devices has been achieved to control. e segmented installation technology of the building height partition and the reverse construction of the curtain wall support structure has been adopted in the installation process of the peripheral flexible structure system, which realizes the lean installation of the ultrahigh altitude and complex working conditions of the curtain wall support structure. e "main operating platform structure" and the "sub-operation platform structure" constitute a modularized integrated, computer-synchronized, and intelligently controlled descending installation platform system which is adopted as main technical method. e digital model analysis technology can be used to realize the precise installation of more than 140,000 m 2 area and more than 20,000 glass curtain walls at one time [48].

Innovation in Shanghai Tower
e Shanghai Tower is a skyscraper integrating commerce, exhibitions, offices, hotels, and tourism at a height of 632 meters. It is the only building in China that has exceeded 600 meters in height. e design of the building breaks through the horizontal city tradition, and a double-layer glass curtain wall system is adopted to construct a new concept of a vertical city, which has achieved the goal of a world-class quality project of green building, wisdom, and humanity [49,50].

Innovative Technology.
e Shanghai Tower breaks through the traditional cascading concept in architectural design. It has set up 9 vertical communities and 21 aerial activity squares at different heights and regions and built a new vertical city new model of super high-rise buildings. e vertical city created by the Shanghai Tower is to form numerous public aerial activity squares between the enclosed double-glazed curtain walls, which is used for citizens to communicate in the aerial public activity square. In terms of structural design, a giant structural system integrating the main structure and the suspension structure was used innovatively. is rigid-flexible structural system was applied for the first time in super high-rise building construction [51,52]. e architectural geometry of Shanghai Tower is determined based on comprehensive aerodynamic test research. rough wind tunnel tests of many building models with different rotation angles, a curved building exterior with 120°torsion has been innovatively designed. On the basis of effectively reducing the effect of wind load by 24%, the best combination of aesthetics and wind engineering has been realized.
e new mega structure system has been adopted in the Shanghai Tower. e connection point between the outer flexible structure system and the internal rigid structure system is neither a simple hinged connection nor a simple rigid connection, and its forces are very complicated. Five types of connection methods have been determined to satisfy the restraint release and deformation absorption between interconnections based on systematic analysis and research [53]. For the five connection methods, five types of flexible connection sliding bearing devices have been innovatively developed to effectively ensure the deformation coordination of the two different rigid and flexible structural systems in complex working conditions. e stainless steel and chromium-molybdenum alloy steel have been adopted in the sliding bearing device to make the antifriction shell, copper base material inlaid alloy to make the slip ring and nanodiamond coating, which meets the requirements of high precision, high performance, and high-quality friction performance. e synergistic effect of the innovative new suspension structure system and the sliding bearing system realizes the "vertical city" function of the double-skin curtain wall [54].

Digital Construction.
A super high-rise digital construction technology system composed of digital model analysis and calculation, special technology platform, collaborative management and control platform, operation and maintenance management platform, etc. has been established in the Shanghai Tower. Fine digital design, fullprocess digital construction, and efficient digital operation and maintenance run through all the main links of project construction, achieving efficient control of the control elements of project construction, and open a new model of super high-rise digital construction [55,56].

Green Construction.
Shanghai Tower took the lead in establishing a green super high-rise building technology system with 600-meter level [57]. Integrating new green building technologies, the energy saving rate reaches 54.3%, the water saving rate reaches 43%, the utilization rate of underground space is 14 times, and the annual carbon emission is reduced by 25,000 tons, which created the world's first super high-rise building with dual certification of the highest level green building of Chinese three stars level and US LEED-CS standards. 7.5. Humanistic Construction. Many innovative approaches have been integrated in the Shanghai Tower in terms of humanities. During the operation and construction of Shanghai Tower, a strong humanistic atmosphere has been built in the public activity space of the "vertical city." e party building activity room in the building, Shanghai Eyes, Guanfu Museum, top sightseeing hall, Michelin restaurant, and sky library, as well as Chinese gardens, landscapes, ceramics, stone carvings, cloisonné, glazed walls, celebrity sculptures, etc., create a cultural environment, which makes Shanghai Tower a unique super high-rise building [58,59].

Conclusions
Looking forward to the development of super high-rise building construction technology, building a digitally driven construction technology system, and striving to change traditional construction methods to comprehensively improve the level of engineering construction have become an inevitable trend in the development of construction technology. e ultimate goal of the digital construction technology system is to realize the whole process of virtual simulation construction on the computer. Intelligent construction will be the most effective way to achieve highquality development in the construction industry in the future. Digital construction technology can promote a qualitative leap in the construction industry and help China transform from a large construction country to a construction power.

Data Availability
No data were used to support this study.

Conflicts of Interest
e authors declare no conflicts of interest.