Arch of La Defense
The La Défense Arch (French: Arche de la Défense) or Great Arch (French: Grande Arche) is an office building located in the business district of La Défense, west of Paris, in the territory of the municipality of Puteaux. Inaugurated in 1989, on the bicentennial of the French Revolution, under the name Great Arch of the Fraternity (in French: Grande Arche de la Fraternité), and built along the historical axis of Paris, it was one of François Mitterrand's Grands Projets, carried out during his first term as president of France.
History
Idea and contest
Two presidents of France had the project of marking the historical axis of Paris with a monumental architectural work: Georges Pompidou (with a project by Ieoh Ming Pei, another project by Émile Aillaud and above all the Tour Lumière Cybernétique by Nicolas Schöffer), and Valéry Giscard d'Estaing (with a project by Jean Willerval). However, it was finally President François Mitterrand who materialized this idea, under the name Projet Tête Défense.
Serge Antoine, advisor to the Court of Auditors and passionate about futurology, was in charge of specifying the program for this project. In his report, delivered in March 1982, he estimated the cost of the operation at 2,000 million francs, to which another 276 million had to be added for the preparation of the land and 300 million more as opportunity cost. On July 1, 1982, Roger Quilliot, Minister of Urban Planning and Housing, and Robert Lion, President of EPAD, convened an international architecture competition, to which 424 anonymous projects from all over the world were submitted, of which the jury he selected four and presented them to the president. On May 25, 1983, François Mitterrand, in accordance with the proposal of the jury, chose the project of the Danish architect Johan Otto von Spreckelsen, professor at the Royal Danish Academy of Fine Arts, an unknown architect without a studio, but whose proposal seduced for its fetish shape, on which he had worked for many years, a cube open to form a large arch. To respond to the technical requirements, Spreckelsen teamed up with the Danish engineer-designer Erik Reitzel, who realized that for to install the foundations of the arch, it was necessary to respect the highway and the railway lines present in the subsoil. Spreckelsen then had the idea of placing the cube not exactly aligned with the historical axis, but at an angle of 6.30° with it, thus giving depth to the monument.
Relations between Spreckelsen and his clients (the Ministry of Public Works, EPAD, the company that managed the communication center and the Caisse des dépôts et consignations) were difficult. The competition regulations stipulated that if the winner was a foreigner, he had to be helped by a French technical team, more familiar with the national administrative machinery. The Danish architect decided in January 1984 to entrust the responsibility of the construction to Paul Andreu. Carried out by the French public works company Bouygues, the works began in 1985, and two thousand people worked on them. In April 1986, the new government of Jacques Chirac questioned the public nature of the building and abolished the Carrefour International de la Communication ("International Center for Communication"). Spreckelsen, upset by the denaturing of his project, he resigned and died a few months later.
Construction
The construction of the Arch of La Défense was one of the greatest challenges encountered for the realization of a building. The main difficulties were related to the design of the structure, the choice of construction methods and the difficulties in meeting deadlines. The works lasted four years and two thousand workers worked on them. The works directors, faced with such challenge, they wanted to carry out a job of quality and precision. In the words of the general director of the construction company, Bouygues, «the Arch of La Défense is at the same time a building that houses offices, exhibition rooms... and a monument whose foundations, structures and lights posed technical difficulties worthy of a great work". The works were supervised by the architect Paul Andreu, who replaced Johann Otto von Spreckelsen. When completed, the Arch of La Défense is in the shape of an open cube 106.9 m wide, 110.9 m high and 112 m long, and contains a total of 37 floors.
The design of the structure
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The main aspects studied were the foundations, the support devices and the calculations (structure, nodes, reinforcements…). These studies resulted in the realization of three thousand five hundred plans of the structure, necessary for the realization of the building.
The 300,000 tons that the building weighs rest on twelve support points, which are concrete piles. Each pile therefore supports a weight of the order of four times that of the Eiffel Tower. The base of these piles is thirty meters below ground level, on top of a forty-foot-thick layer of limestone, which in turn lies on top of a forty-one-meter-deep layer of loam. It was the first time that a building capable of supporting these loads had been built in La Défense. To check the results of the calculations of the settlements, during the works, measurements of these settlements were regularly made, which were always lower than the calculated estimates.
The piles are surmounted by capitals that support the structure of the building. To absorb the dimensional variations due to deformations and expansions, as well as vibrations induced by road and rail traffic, forty and eight neoprene plates between the capitals of the piles and the structure of the building. In addition, devices were placed to be able to change these plates throughout the life of the building. To validate the proposed technical solution, a model identical to the final solution was made. In the same way that an urban legend states that there are hydraulic cylinders at the foot of the Eiffel Tower, misinformation was spread about the presence of hydraulic cylinders to support this building.
Taking into account the coexistence of reinforced concrete parts and prestressed concrete parts, the need to provide a three-dimensional section of the building, and the large number of calculations required to evaluate the seats, a very complex modeling had to be carried out. building detail. This model rested on an array of 11,000 bars and 6,500 nodes.
These calculations showed the need to install a device on site to maintain the two "legs" of the building vertically until the upper platform (the arch lintel) was placed, since it is this platform that ensures the building stability. For this reason, four reinforcements equipped with hydraulic cylinders of two thousand bars each were placed on the fifteenth floor, which were maintained until the end of the works.
Building methods
In this sense, the greatest difficulty was conceiving the means of production and transport to the site of the 150,000 m³ of concrete necessary for the 220,000 m² of slabs. For this reason, numerous innovations were developed to carry out this delicate project, in particular the organization of a construction cycle over four days and the realization of the upper platform.
The only repetitive part of the construction resided in the legs, which housed 50% of the slabs to be built. In order to meet the deadlines imposed, it was evident that the two floors of the same level of each leg had to be built simultaneously in four days. Despite the fact that the organization that had to be established is the usual one in a classical building, the complexity was great, and it was due to elements such as the load-bearing megastructure, made up of 1.7-meter-thick walls that surround the service ducts; pinion walls attached to other service ducts; and the facades in concrete lace, which had to be made with great precision to allow the future placement of the glass panels.
Eleven tower cranes were installed on the site: eight for the construction of the infrastructures, four for the construction of the base, four for the construction of the two legs, and two for the construction of the upper platform. The height of the formwork of the mega-beams of the base and the ceiling was nine meters. Taking into account the lack of space, the installation and later the use of the cranes had to be precisely organized. To avoid saturation of the cranes, all the concrete was poured with pumps. The organization had to deal with the unexpected and it was unthinkable to be delayed for half an hour, at the risk of jeopardizing a whole day. Particular attention was paid to the daily availability of formwork and tools.
The construction of the upper platform was also a great challenge: it involved placing more than 30,000 tons of concrete at a height of about one hundred meters, above the hollow of the arch. The upper platform rests on four mega -Prestressed beams 110 meters long, 70 meters wide and 9.5 meters high, each of which weighs 2,500 tons. To build them, a 90-meter-high and 70-meter-wide rolling gantry was installed width. This imposing tool was crowned by tracks on which the ten-meter-long formwork circulated, which allowed the beams to be made in seven sections. Each of these sections consisted of more than 100 cubic meters of concrete, which caused very high pressures on the formwork. Once each beam was made, the concrete was prestressed, and later the entire frame was moved 21 meters to allow the construction of the next beam. There are other secondary beams of the same height that connect the main beams and end in the corbels that support the marble eardrums of the building. The placement of these 25 meter cantilever corbels was also extremely complex.
Building difficulties
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The main difficulties encountered during the execution of the works were due to the lack of space, the large number of complex jobs that had to be managed, the demands for speed of execution and the necessary precision.
The main difficulty was due to the fact that the largest building in La Défense was built in an area already highly congested on the surface due to numerous completed and occupied buildings and important traffic routes such as the circular boulevard, but also on the ground due to the lines of the Paris Metro, the RER, the highways and a SNCF track. Taking these limitations into account, it was necessary to organize in detail the implementation of the vertical transport systems, the provisional support areas, and the circulation areas for machinery and personnel. A section of highway was also used that was not yet in service, but was several hundred meters from the work.
The activities of the work and the duration of each of them had been specified in detail before the start of construction. The most delicate requirements to respect were those related to the construction of the mega-structures and, above all, those related to the four-day cycle of the plants. This cycle was made up of a multitude of interdependent tasks, carefully planned, but subject to a large number of risks, particularly the wind, which slowed down the maneuvers for placing the formwork.
The calculations made to dimension the pieces of the structure had produced important requirements about its realization; This raised the difficulty of reconciling the demands for speed of execution with the required precision. Among these numerous requirements, one can mention those due to the prestressing of the concrete, which —for example— causes a 4 cm shortening in a 110-meter-long beam. This precision was also necessary for the placement of the 25,000 m² of anti-reflective glass and the 35,000 m² of Carrara marble that cover the facades. The exterior faces of the building are covered by 5 cm thick glass plates, specially treated to prevent any optical deformation and to resist the wind.
Opening
The inauguration of the building took place in July 1989, two years after the death of Johan Otto von Spreckelsen. The year 1989 was marked by major celebrations such as the centenary of the inauguration of the Eiffel Tower, and the bicentennial of the French Revolution and the declaration of the rights of man and citizen. The opening of the building to the public on August 26, 1989 coincided precisely with the commemoration of this last event. In addition, the G7 summit was held at the same time.
Exploitation
In 2007, the government considered grouping the Ministry of Public Works headquarters in a new tower within the framework of the reactivation plan for the financial district of La Défense, and proposed financing this operation with the sale of the surface it occupied at the Arch of La Défense. The protection of the building as a monument historique was also studied, with the aim of preserving its architecture.
On April 24, 2010, access to the roof of the arch was closed to the public. Indeed, the fall of a pulley on April 4 forced the ministry to immediately suspend the use of the panoramic elevators for security reasons. security. From April 4 to April 24, visitors had been allowed to access the museums via elevators located in the arch columns. The ministry also launched an audit to find out the exact causes of this accident, and the elevators were repaired over the summer.
The ministry first announced a four-month delay in reopening, and then a reopening in January 2011. It finally announced that it intended to permanently close the arch to the public and transform the arch's roof surface into offices and lounges depriving the Hauts-de-Seine of its most visited monument, with some 250,000 visitors a year. The closure of the roof led to the dismissal of about forty people. In 2013, the legal process of expulsion from the operating company began of the arch roof, making the ministry the official owner of the roof.
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On December 3, 2014, Olivier de Guinaumont, Project Director at Eiffage, announced the launch of a renovation project for the Arc de La Défense, with an estimated budget of €192 million. This project aimed to completely remodel the interior of the south pillar, reopen the roof, and replace the marble on the façades and stairs with granite, as it was deteriorating due to "grain breakage", accelerated by air pollution. This renovation was completed. in March 2017. The State became the bare owner and paid Eiffage in the form of free rent for twenty years. On September 12, 2016, fifteen renowned architects criticized, in a forum of Le Monde, to the owners of the north wall of the building because "they decided not to coordinate with the works carried out by the State, and even replaced the missing marble plates with enameled plate plates of the same colour". They also asked the State to ensure the protection of the great monuments that he himself had contributed to build.
On June 16, 2017, following the completion of the renovation work on the south pillar and roof, and after eight years of closure to the public, the arch reopened with a 1,200 m² exhibition space dedicated to photojournalism, a auditorium and a restaurant. Two new elevators were also added.
Architecture
Situation
The Arch of La Défense is located in the historical axis of Paris, or royal road, where it is accompanied by other monuments such as the triumphal arch of the Star, the obelisk of the Place de la Concorde, the Tuileries Garden, the triumphal arch of the Carousel and the equestrian statue of Louis XIV in the Napoleon courtyard of the Louvre Palace. However, in reality the Arc de La Défense makes an angle of 6.30° with the axis, due to two reasons:
- First, from a technical point of view, Erik Reitzel had to install the foundations of the arch structure respecting the highway and the railway lines existing in the subsoil, as well as the project of extension of line 1 of the Paris Metro,
- On the other hand, from a symbolic point of view, Johan Otto von Spreckelsen approved the turn of 6.30° because it valued the volume of the cube and recreated the existing turn between the Cour Carrée the Louvre and the historical axis.
Shape
Johan Otto von Spreckelsen and Erik Reitzel envisioned the Arc de La Défense as a 20th-century version of the Arc de Triomphe in Paris, but in this case it would be a monument dedicated to humanity and humanitarian ideals rather than victories military. The arch took the form of a cube hollowed out at its center, measuring 112 m in length, 106.9 m in width and 110.9 m in height. The interior hollow accommodates the Notre Dame Cathedral. The building resembles a hypercube in four dimensions that is projected into the three-dimensional world.
Materials
Johan Otto von Spreckelsen and Erik Reitzel used high-quality materials for the work: pre-stressed concrete with silica fume, which combines strength and flexibility, 25,000 m² of anti-reflective glass, 35,000 m² of Carrara marble… However, marble turned out to be too porous, so it absorbs water, swells and disengages. The gray marble on the north and south façades had to be replaced with granite ten years after it was built, and the white marble on the east and west façades experienced the same problem. The outer faces of the arch are clad with glass plates of 5 cm thick, specially treated to prevent any optical deformation and resist strong winds. The other faces are covered with slabs of white Carrara marble and gray granite.
Utility
In 2007 the Ministry of Ecology, Sustainable Development, Transport and Housing owned the south pillar, the roof and the two monumental stairs. AXA and the Caisse des dépôts owned the north pillar. The roof of the Arc de La Défense housed, until its closure to the public, a congress and exhibition center, the Museum of Informatics, the Video Game Museum, the Toit citoyen club, the ô110 gastronomic restaurant and a viewpoint that offered a panoramic view of the entire La Défense district and western Paris. These facilities could be accessed by means of a group of panoramic lifts located in the hollow of the arch.
Starting in 2009, the IÉSEG School of Management installed its Parisian campus at the base of the Arc de La Défense, replacing the information center on Europe called Sources d'Europe, which closed opened its doors in June 2004 but whose funds were transferred to La Documentation française. The Bureau d'Enquêtes sur les Événements de Mer) is based on the southern pillar of the Arch of La Défense.
Transportation
The Arch of La Défense is served by:
- Line A of the RER, Lines L and U of the Transilien and Line 2 of the Paris Tram, through the Station of La Défense;
- Line 1 of the Paris Metro, through the La Défense station;
- 15 RATP bus lines;
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