 | | |  | | | Innovative Technology as Metaphor | | Dresden's Frauenkirche returns from Expo 2000 to Dresden As metaphor for the destruction and subsequent reconstruction of an epochal church, as testimony of the innovative use of technology and materials and commitment for a future bound to an historic past is how artists and initiators perceive this outstanding installation.
The art installation "Reconstruction Frauenkirche" in front of the German Pavilion at the World Exposition Expo 2000 is based on the power and precision of hydraulics.
The reconstruction of Dresden's renowned Frauenkirche, which was destroyed in 1945, enjoys international recognition and attracts worldwide support. For the presentation of this project in front of the German Pavilion at Expo 2000 in Hannover, one opts for an idea stemming from Bernhard Buderath and Werner Lorke.
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| | Objectives were twofold: to do justice to the architectural highlights of this ca. 100m high church, first completed in 1743, as well as to the motto of the World Exposition "Nature, Humankind, Technology". Motivation for the project "Installation Reconstruction Frauenkirche Dresden" was provided by the Board of Dresdner Bank. Already demonstrating outstanding commitment for the actual construction work in the Saxony state capital, the Bank also undertook the financing of the project in Hannover.
The reconstruction of Dresden's renowned Frauenkirche, which was destroyed in 1945, enjoys international recognition and attracts worldwide support. For the presentation of this project in front of the German Pavilion at Expo 2000 in Hannover, one opts for an idea stemming from Bernhard Buderath and Werner Lorke.
Objectives were twofold: to do justice to the architectural highlights of this ca. 100m high church, first completed in 1743, as well as to the motto of the World Exposition "Nature, Humankind, Technology". Motivation for the project "Installation Reconstruction Frauenkirche Dresden" was provided by the Board of Dresdner Bank. Already demonstrating outstanding commitment for the actual construction work in the Saxony state capital, the Bank also undertook the financing of the project in Hannover.
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| | | The cupola is constructed in square tubes of bright aluminium alloy. It consists of 16 identical vertical segments arranged in symmetric rotation, whose tubes together depict opposing, interlocking spirals. | |  |
| | | A synchronous tolerance of maximum 1% may not be exceeded. To guarantee this tolerance all four telescopic cylinders were fitted with travel measuring systems. | |  |
| | A circular, two-level stonework plinth in black basalt lava forms the base for a ring of eight columns, which support a double band of curved HEB profiles at a height of 6.5 m. Above this rises - in its literal sense - a movable cupola in anodized light metal. It opens in silent motion powered by four hydraulic cylinders. While this brilliantly lustrous construction slowly rises, it changes shape. Thanks to its polygonally formed latticework, the compact folded ring metamorphoses into a contour that recalls the characteristic silhouette of the Frauenkirche's famous "Stone Bell". The principle applied for the cupola stems from the American artist Chuck Hoberman.
At the centre of the plinth area a glass showcase safeguards a finely crafted architectural model of the church in its projected form of reconstruction in the scale 1:75.
Synchronized with the mechanical movement of the cupola are musical compositions that underline the sacral context of this art installation.
Responsible for both the overall planning, as well as for the coordination of the project through to "turnkey" handover, was the Frankfurt company iO Interdisziplinäre Objekte. Just nine months were available from placing the order through to project completion. Therefore the "friction-free" coordination of the various subdivisions was particularly important. Manufacture of the steel base construction took place in Hannover, whereas the cupola - without base - was completely produced and assembled in New York, where it also underwent a one-month testing period. To this purpose the hydraulic drive system, including the electronic controls, specially produced for the project in Germany by Universal Hydraulik GmbH, had to be temporarily transported to the USA. This transatlantic coordination of the constructive and engineering requirements was facilitated by all-embracing CAD-based planning and electronic data interchange.
In its extended state the installation has a diameter of 5.2 m and height of 10.3 m. Contracted, its diameter is 6.4 m with a height of 7.5 m.
A polygonal ring in double 240 U-profile serves as foundation. The columns are bolted to the base and the upper double band by head and base plates. Held together by crossplates, the columns in four steel angles form an open inner quadrature. Design objective was to achieve a solid and likewise transparent-like column construction whose number and arrangement calls to mind the eight columns of the famous Dresden church.
The cupola is constructed in square tubes of bright aluminium alloy. It consists of 16 identical vertical segments arranged in symmetric rotation, whose tubes together depict opposing, interlocking spirals. Every four tubes, which jointly merge into a scissors-like swivel connection, form a constructive basic unit. The pertinent opposing tube ends are riveted with so-called hub elements. To generate the desired contour, the axes of the horizontal adjacent hubs/swivel connections must be contrastingly oriented in space. The fact that the alignment of the axes remains constant during the entire movement is part of the patented development by C. Hoberman.
The hydraulic cylinders are supported by four slides.
Dead weight and live load of the cupola are transferred via 16 radially displaceable slides running on roller bearings in the subconstruction. Four of these slides additionally support the 3-stage hydraulic cylinders of the firm Universal Hydraulik GmbH. The piston rods of these cylinders each engage at a hub connection in the vicinity of the upper edge of the cupola. Extremely high demands are placed on the parallel motion and operating safety of the cylinders. A synchronous tolerance of maximum 1% may not be exceeded. To guarantee this tolerance all four telescopic cylinders were fitted with travel measuring systems. Each cylinder is reset in its true position by a computerized servo-valve. Both the true position as well as the true speed are prescribed by an overriding computer, which also controls music and sound.
With total displacement of 2,540 mm the synchronous requirement amounted to only 1%. Typical figures of 0.2% can be achieved in practice.
The control algorithm was specially developed for this specific application. Key problems were the transition points of the individual telescopic stages of the cylinders. The artist placed stringent demands on a harmoniously sliding transitory movement. In close cooperation with the technical authority TÜV Nord, Universal Hydraulik GmbH defined individually independent safety thresholds, which when exceeded result in the automatic switch-off of the system.
Switch-off criteria are:
Positional deviations > 2mm
Pressure deviations of individual cylinders > 20 bar
Synchronous error > 2%
Independent of the computerized evaluation of the deviations, three special light barriers were installed to monitor positions and guarantee a hardware-switch-off of the system.
The entire hydraulic plant including overriding control from the firm Universal Hydraulik GmbH was housed in a separate room in the basement garage of the German Pavilion. Thus the distance between the pump drive and the actual installation amounts to ca. 50 m. Fluid pipes were laid subterraneously and operated at a maximum pressure of 10 MPa (100 bar) due to the long distance.
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| | Dead weight and live load of the cupola are transferred via 16 radially displaceable slides running on roller bearings in the subconstruction. Four of these slides additionally support the 3-stage hydraulic cylinders of the firm Universal Hydraulik GmbH.
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| | | The control block with the servo-valves was arranged in the main foundation of the church model. | |  |
| | To cut service and maintenance requirements an additional remote monitoring system via the telephone line was set up with the firm Universal Hydraulik GmbH. This enables machine conditions to be monitored and checked for deviations.
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| | Hand-in hand cooperation: The company IO, Frankfurt, designed a pavilion on behalf of Deutsche Bank, which was intended to symbolize the cupola of Dresden's Frauenkirche. Following its successful presentation at Expo 2000 the model will be on display until at least the year 2005 in Dresden, most likely at the airport. Goal of this promotion is to win further sponsors for the reconstruction of Dresden's Frauenkirche. Universal Hydraulik GmbH, Neu-Anspach, planned and manufactured the entire hydraulic and electronic control, incl. stainless steel telescopic cylinders, hydraulic drive system and command centre.
Werner Lorke (IO)
Karl-Helmut Müller (U.H.)
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