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Diskussion
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ußgängerbrücke, Stalhille 2004, Architekten, F Tragwerksplaner: Ney & Partners 7 Merchant Square Fußgängerbrücke, London, 2014, Arch.: Knight Architects, Tragwerksplaner: Peters & Cheung and Eadon Consulting, AKT2 8 Slauerhoffbrug, Leeuwarden 2000, Architekten: Van Driel Mechatronica 9, 10 Fahrrad- und Fußgängerbrücke Innenhafen Kopenhagen 2016, Arch.: Studio Bednarski, Tragwerksplaner: COWI, Hardesty & Hanover 6
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examples, the supporting construction can vary in much the same way as with fixed bridges – from girder grid to bowstring arch or skeleton-frame. The Pont Gustave Flaubert in Rouen is an unusual variation on the vertical-lift type. It consists of a pair of towers with bridging decks on each side that can be raised independently of each other to a height of 55 m. The new Botlek Bridge in Rotterdam has a 49-metre-wide carriageway divided into two separate lengths one behind the other and each spanning a distance of 93 m. With a weight of 10,000 tonnes (the greatest in the world and equivalent to that of the Eiffel Tower), the bridge was designed with four traffic lanes, two service lanes and two railway tracks. The lifting and closing movement over a height of 31 m is operated roughly once an hour and takes less than two minutes. That amounts to 9,000 opening operations a year. With movable bridges, reinstatement, constructional changes and their effect on the design are usually implemented pragmatically in view of the requisite sychronization of the
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Pedestrian bridge, Stalhille, 2004 structural engineers: Ney & Partners 7 Merchant Square footbridge, Paddington Basin, London, 2014; architects: Knight Architects with Peters & Cheung and Eadon Consulting, AKT2 8 Slauerhoffbrug, Leeuwarden, 2000; architects: Van Driel Mechatronica 9, 10 Bicycle and pedestrian bridge in inner harbour of Copenhagen, 2016; architects: Studio Bednarski structural engineers: COWI Hardesty & Hanover
movement. It is logical, therefore, to adopt the same mechanism. One sees this in the new parallel routing of the existing Kattwyck Bridge in Hamburg, where Leonhardt Andrä and Partners have closely followed the existing lattice-frame lifting structure dating from 1973. Bascule bridges The simplest bascule bridges are those that rotate about a single horizontal axis. Nowadays they are hydraulically or electrically operated, although earlier examples of steamor gas-driven structures or even manually controlled forms still exist across narrow streams or canals. In the classical Dutch bascule bridge, the counterweight is situated above the deck and forms part of a clearly legible mechanism. In addition to well-known examples like Tower Bridge in London or the typical two-arm cantilevered type found in Chicago, where the counterweight is at the point of support, many individual mechanisms have been designed for specific locations. In the case of the two Bellmouth Passage
bridges in the London docklands by Wilkinson Eyre and Jan Bobrowski and Partners, the entire operating mechanism is concealed beneath the deck, so that the structures are not recognizable as being movable. The bridges rotate about the horizontal axes of two large steel rings mounted on roller bearings with a counterweight, through which runs a permanent pedestrian walkway. For the new Merchant Square footbridge over Paddington Basin in London, Knight Architects and AKT2 attached great importance to sculptural expression (ill. 7), reflecting the wishes of the client. The three-metrewide deck is divided into five hydraulically operated horizontal steel beams, the pivoting axes of which are slightly offset to each other. This and the fact that the five “fingers” are raised at different speeds and with different opening angles creates the impression of a fan. The cantilevered arm of the unique, fully automatic Slauerhoffbrug in Leeuwarden, the Netherlands, also known as the “flying draw-