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STRUCTURE AND LIGHT 175▲ 8.13 Trade Fair Glass Hall, Leipzig, Germany, Ian RitchieArchitects, 1996. Exterior trusses support the vaulted grid-shell.▲ 8.14Trusses and the grid-shell as seen from within the hall.▲ 8.15 Cité des Sciences et de l’Industrie, Paris, France, AdrienFainsilber, 1986. Les Serres or conservatories on the main façade.▲ 8.16 A hierarchy of prestressed cable-beams resist faceloadson the glazed walls.radial view met our adopted criterion of no more than 15 per cent. (Thispercentage arrived at by analyzing many of the glass structures we havedesigned, represents the maximum interference which allows the overalldesign to have a strong feeling of lightness.) 10Even though completed back in 1986, the three glazed conservatoriesknown as Les Serres on the southern façade of the Cité des Sciences etde l’Industrie, Paris, still represent a fine example of structure designedto maximize light (Figs 8.15 and 8.16). Finely detailed horizontal cablebeamgirts span 8 m between vertical steel posts to support face-loadsacting on the 2 m square glass panels. An enlarged version of the girtstransfers horizontal loads from the intermediate vertical posts to eachside of the 32 m wide bays. Prestressing the catenary cables to limit thenumber of structural members acting in compression has enabled this