Art museums and cultural libraries are first dominated by concerns for their collections, and second, by accommodation of visitors as they roam through the facilities. Security, environmental control with an emphasis on humidity levels, artificial and natural lighting, circulation, and storage are all vital. Live load allowance for exhibit spaces was set at 102 lbs/ft2 (500 kg/m2)
As a national culture center, Beaubourg would also have significant popular importance and serve as a nerve center for the country’s artistic interests. Gestures of great magnitude were required to recognize and serve the high status of the building’s prominent position.
Finally, Centre Pompidou is a museum of modern art. Classical works are collected at the expansive Musee de Louvre, which is only a short walk from Centre Pompidou to the west, past Les Halles.
The French ministries wanted the project to be completed by November 1975, largely because Georges Pompidou wanted the building completed before the end of his presidential term. Consequently, the site was excavated in
March 1972, two years before the design was completed. Construction continued during design development at the rate of about $3 million (£1.5 million or FF 20 million) per month. Speed, accuracy, and decisiveness were paramount throughout the project’s evolution. Further, the original brief for the building essentially relegated the architect’s work to design of the facades and structure. Piano+Rogers had to negotiate to gain control of interiors and furniture. Debates about the plaza and other parts of the project were ongoing.
Placing the center within its environs was also a challenge. It was assumed that most people would come by car, so 700 spaces were allocated for parking. Connection to the existing metro line was also important and would help merge the center into the everyday experience of local neighborhoods. Furthermore, there was a matter of scale. Huge floor area requirements, extensive ceiling heights, and the desire for a large plaza around the building combined to increase the overall height and mass of the building beyond the legal limits of the building code. The building mass also threatened to outgrow the stature of the existing five – and six-story urban fabric.
The architects’ “Live Center of Information” interpretation of the program fell into a period of uncertainty following the 1968 student political uprisings in Paris. Part of the motivation for the cultural center may have been stirred by those events, just as some of the world’s fair expositions were motivated by domestic appeasement. Consequently, there was a lack of will on the part of the client to empower the potent media aspects of the architect’s intention. Who would control what information was displayed? How would the messages be formatted? These questions gave Pompidou’s ministries pause for concern.
Turning the building inside out, as it were, exposed the technical systems and released the interior loft floors for flexible use. Although serving the main architectural intentions quite well, this decision also posed problems. What would it take to span 157 ft (48 m), and how would the structure be fireproofed? How would view and day – lighting work? How would the exterior be finished, and how would it be cleaned?
The megastructure scale of the building added a new dimension. More than 60 percent of the 14,560 tons (13,000 tonnes) of structural steel was of rolled, cast, or forged steel exceeding 6.3 in. (160 mm) thickness, and this was quite unusual for building construction. The steel casting industry in particular was unfamiliar with architectural requirements. No one on the team had experience with a building structure of this scale, and all of their previous experience had to be viewed with some caution.
Appropriate Systems
Peter Rice visited Kenzo Tange’s cast steel Metabolist megastructure in Osaka, Japan, in 1971. It was the featured Expo 1970 space frame Festival Plaza pavilion designed by Kenzo Tange and Professor Tsuboi (see introduction to Chapter 8). The Metabolist’s work would also have an influence on Norman Foster’s Hong Kong and Shanghai Bank (see case study #25). In addition, Expo 70 was big on information technology, interactive displays, and huge data screens.
A merging of information and architectural technologies was originally rooted in the central tenets of Archigram, a group of young graduates who published techno-utopian manifestos from about 1961 to 1974. Their work took the form of futuristic drawings and terse declarations that read like telegrams, hence “Archi-gram.” Led by Peter Cook, David Greene, Michael Webb, Ron Heron, Warren Chalk, and Dennis Crompton, they proclaimed an agenda in which, in the words of David Greene (Wolfe, 1999), “nomadism is the dominant social force; where time, exchange and metamorphosis replace stasis; where consumption, lifestyle and transience becomes the programme; and where the public realm is an electronic surface enclosing the globe.” If this sounds prophetic of the Internet as we know it entering a new century, it was certainly portentous and pregnant with possibility when Piano + Rogers wrote the competition statement for Centre Pompidou.
Below-grade substructure work was expedited by detailed programming work under preparation for two years before the competition was awarded. The architects’ winning design pushed the building footprint against the eastern boundary of the site, but everything from Rue du Renard to the western edge of adjoining buildings, and from the St. Merri church to the south to the northern edge of the property, was hollowed out to the depth of four or five floors, reaching down 196 ft (60 m). The underground work led to the development of a large cover at surface level that formed an interconnected set of exterior spaces. The largest of these is the sunken main plaza in front of the building that covers the main garage area. This plaza leads gradually down to the building entryway one level below the surrounding streets. The slow slope of this plaza is usable as an amphitheater but not so steep as to prohibit outdoor exhibits. Two 7 m video screens were originally planned to be arrayed on the wall frame above. Large air ducts rise on the tree-lined western site boundary from the parking garage to visually claim the plaza for
the Pompidou center. Other parts of the plaza flow south to St. Merri across a large fountain pool in front of the IRCAM, further west along a broad pedestrian axis and park leading to Les Halle and north to encompass the end of the site where Brancusi’s studio was permanently relocated. Most of the buildings that front these exterior spaces have been converted to commercial uses opening onto the plaza, effectively binding the Pompidou back into its fabric.
Below-grade construction was started by boring along the perimeter and inserting steel sections. The bottom portions of these holes were filled with concrete to anchor them structurally, and the upper parts were filled with weak grout that could be easily replaced with shoring between the steel sections as excavation progressed. Bearing foundations for the building’s main columns were set on reinforced and posttensioned concrete wall footings
29.5 ft long by 3.3 ft wide by 45.9 ft deep (9 m X 1 m X 14 m). Each footing was reckoned to carry a vertical load of 4,000 tons and moment loads of 18,000 ton m.
There are six floors of 23 ft (7 m) floor-to-floor height above grade spanning 157.5 ft (48 m) with 9.3 ft (2.8 m) deep lattice trusses. In plan the superstructure of the building consists of three zones forming a footprint of 196.9-ft X 550.2 ft (60 m X 167.7 m) in 13 bays of 42.3 ft (12.9 m), about 26,412.8 ft2 (2,452.6 m2) overall. The middle zone contains the 157.5 ft (48 m) clear span across the building interior between the main columns. The outside two zones make up structural wall frames to support and cantilever the main span lattice girders. These outer frames visually resemble oversized scaffolding. The inside wall frame support consists of 34 in. (850 mm) diameter steel tube columns, which were delivered to the site in two sections and welded together after erection of the lower elements. Each column has a tapering wall thickness from 3.4 in. (86 mm) at its base to 1.6 in. (41 mm) at the upper level.
Outer tension rod members of 7.9 in. (200 mm) solid steel in the wall frame act to reduce the bending moments on the center of the span by producing a 19.7 ft (6 m) cantilever outside the main columns. This cantilever force acts through horizontal 9.6 ton cast steel gerberette beams that are threaded around the main columns. Compression forces in the top chord of the long-span lattice trusses are thus transferred through the main columns without acting on them laterally or torsionally. Instead, the compressive shortening forces in the trusses move through the gerberettes and are transferred in tension down the outer frame wall rods to the foundation. Consequently, rotational forces on the columns are greatly reduced and they are required to act only in pure compression. Each of the 28 total assemblies of compressive column-to-gerberette – to-tension bars rest on one of the 29.5 ft X 3.3 ft X 45.9 ft (9 m X 1 m X 14 m) deep concrete wall footings.
The frame is stiffened laterally by cross bracing in the vertical plane across the long facades attached to the ends of the gerberette beams. Stiffening in the other vertical plane is added by diagonal braces between the lattice girders on both gable walls. Horizontal stiffening is provided by bracing rods between the gerberette ends and the columns at alternate floor levels. Alternate bays of the lattice beams are braced horizontally for torsional stiffness. The floors are constructed of rolled steel sections spanning the 42.3 ft (12.9 m) between bays and act compositely with a 4 in. (11 cm) concrete deck.
|
Figure 10.7 South end wall. |
The lattice trusses are the largest elements of the building. They are literally of bridge construction proportions. Each truss weighs 88.5 tons (79.0 tonnes) and measures 9.3 ft deep (2.82 m) by 157.5 ft (48 m) long. They were formed by two 16 in. (41.9 mm) diameter top chords and two 8.9 in. (225 mm) bottom chords, the double chords being used to reduce the depth of the structure and improve lateral stability. The original contract for the trusses called for them to be brought to Paris by barge and transported from the Seine by trailer. In fact, they were brought by rail to Port de la Chappelle and then trailered to the site at night. Rue du Renard had to be reinforced prior to the start of delivery. The trusses arrived at the rate of three per week and were lifted into place with a single 500-ton-capacity crane that could handle the weight of the trusses out to a 111 ft (34 m) radius. Bays were erected at the rate of one every ten days. Following erection of the trusses, prefabricated floor sections measuring 34.6 ft X 21.0 ft (10.5 m X 6.4 m) were bolted directly to the trusses and concrete decks were poured one bay behind steel erection. The entire structure was erected in eight months.
Fire-resistance requirements dictated a two-hour rating for the steel, meaning that temperatures in the structural members would not exceed 840°F (450°C) after two hours of exposure to a standard fire. This was handled in the columns by filling them with circulating water so that their maximum temperature in any fire would be controlled to below 340°F (170°C). Truss members were wrapped with mineral wool or ceramic fibers and clad in stainless steel. Floor beams were sprayed with a vermicu – lite and cement compound. These passive measures were supplemented by an active fire sprinkler system mounted outside within the wall frames.
The north, west, and south facades are fully glazed to overlook the plaza and provide views from, of, and into the building interior as well as the glazed escalator tubes. From the restaurant terrace on the south end there is a good view toward Notre Dame Cathedral; the Eiffel rises far off to the west across the plaza with traces of La Defense behind; and to the north is a view toward Montmartre and the Basilica of Sacre Coeur. These three elevations are provided with roll-down fire curtains. Because of the service elements outside the east facade, however, that side was unexpectedly required to use solid panels for adequate fire resistance.
Walls on all the elevations are held back 5.3 ft (1.6 m) from the columns and gable trusses to distance the structure from potential fires. In addition, glass wall frames are fitted with metal roll-down shutters, which are activated by fire to protect the external structure from heat coming from an inside fire. The shutters can also be operated manually for solar control.
Heavy equipment, boilers and chillers of the building’s central plant, is located in the basement of the building along with thermal storage water tanks, main electrical distribution gear, and water treatment equipment. These services are distributed vertically within the east wall frame to equipment on the lower levels and finally to the roof level air-conditioning plants and four prominent rooftop cooling towers. Some horizontal distribution occurs across the east facade. This wall frame zone also contains freight elevators opening to the basement service areas and access gantries for servicing. Color coding of the service elements provides legibility and visual interest.
Within each floor level, there are exposed below-ceiling services for air delivery, ductwork, and lighting, as well as above-floor delivery of wiring and small pipes within an 11 in. (280 mm) raised floor resting on the concrete deck. Each bay of interior floor space is an independent thermal
zone that receives air from the rooftop air handlers and delivers it accordingly.
|
Figure 10.8 East service wall from Rue du Renard. |
The central plant has a total cooling capacity of 3500 tons (10 megawatts) and three boilers totaling 6800 kW. There are 26 high-velocity variable volume air handlers on the roof, each feeding conditioned air down to and back from one of the 13 bay widths of each floor. To lower the scale of the rooftop equipment, each air handler is broken down into its component parts: filters, air washers, fans, coils and air vents. Air-handling equipment and the cooling towers cover the east half of the roof. Trumpeted air vents are clearly visible from the east side terraces and the outdoor plaza.
Public access to the museum areas is not from the escalator tubes, as the building exterior seems to suggest, but from doors located centrally at the lower edge of the plaza. A double height interior forum connects the street level with the plaza level in a single volume. This room contains the general reception area, retail facilities, and temporary exhibits on the plaza level. The street-level mezzanine of the forum holds an exhibit area with a cafe to the south of the double height entry reception, plus a large theater to the north. The plaza-level reception area also looks down into a performance-level basement where a theater and meeting rooms are situated. From ticketing booths on the plaza level an interior escalator takes visitors to the street level on the northwest corner of the building. Here a small lobby connects to elevators and the exterior escalator. At this point in the journey, visitors can already look down 46 ft (14 m)
onto the plaza. Four elevators are located at this corner. An emergency exit is located at the bottom end of the two-way escalator tube, and this is left open after museum hours for direct public access to the restaurant and its terrace at the top floor, five levels (115 ft or 35 m) above the street. The 13.1 ft (4 m) diameter escalator tube is suspended outside the 26.3 ft (8 m) wall frame. In reality, the escalator accesses only the mezzanine, level four, and level six. Horizontal circulation platforms occur inside the frame — most of them restricted to staff access and emergency exits.
Levels two and three contain the library. These are reached not from the exterior tube, but from a separate set of interior escalators off the street-level mezzanine. This arrangement is necessary so that the typical measures of control over the book stacks can be exercised. Entry to the museum collections from the escalator is at level four, and an interior stair connects to the rest of the collection on level five. Level five also has a sculpture terrace on the west side, dominated by a shallow reflecting pool, a similar terrace across the south end, and a dry sculpture terrace on the northwest corner outside the emergency exits. Finally, level six is cut away above the three sculpture courts of level five, opening them to the sky. The restaurant and its outside terrace overlook the fifth-level south sculpture garden. Galleries and a small bookstore have a view over the other two terraces. The horizontal walkway in the wall frame of level six is glazed from the southern end to the elevators shafts, affording spectacular views of the low-rise central Paris and outlying grand monuments.
Fire stairs are located at the four corners of the building, and the two on the west generally connect with the horizontal walkways within the wall frame. Four additional fire stairs are placed five bays in from each corner. The top floor is treated like a mezzanine of the fifth level, and the connecting terrace across the south facade connects the two sides of the building for fire egress.
There are no permanent partitions on any of the floors, but a relocatable, bolted-together two-hour firewall divides each typical level into two zones of less than the allowable
106,0 ft3 (3000 m3) compartment size. The trusses were all designed to carry a bolt-on system of demountable mezzanines within the 23 ft (7 m) story height, but because of client disinterest, few of them were ever deployed.