Just before WW2 the French architect Jacques Couëlle invented a system to build structures, using ceramic tubes embedded in concrete, known as Fusée Céramique. During WW2 this system was used in France and Germany to construct barracks and shelters. After the war this system was applied in France, North Africa and The Netherlands to construct low-rise cylindrical vaults and domes for workshops, swimming halls, stations, schools and churches. Thanks to the ceramic infill the need of material and the dead weight of the vaults was minimal. For example in the city of Woerden, The Netherlands, a cylindrical low-rise vault was built with a span of 19,8 m, a thickness of 135 mm and a ratio thickness-span of 1:147. In 2012 this workshop was pulled down. During the sixties the costs of labour were rising and this system could not compete with other systems. Fifty years later most of these structures are pulled down. The remaining buildings do not meet the demands of the present concerning comfort, safety, insulation and need of energy. Nevertheless these structures are a fine example of engineering, so at least some of these vaults have to be preserved for the coming generations. In the past the low-rise vaults were designed for the permanent load and a modest live load. Unfortunately due to temperature variations and time dependent deformations the Fusée Céramique roofs are subjected to internal forces, which can cause cracks and reduce the stiffness and load bearing capacity substantially. Consequently some vaults are not safe and have to be strengthened. This paper describes for cylindrical Fusée Céramique vaults, composed of concrete and ceramics, the effect of the time dependent deformations concerning strength, stiffness, buckling risk and bearing capacity. To strengthen these vaults a cost-effective method is described, using the potentiality of the hangers, connecting the ties with the vaults, to reduce deformations and buckling length. Possibly this method can be used to strengthen and stiffen arches and vaults of concrete, masonry, steel and timber too.@en

This issue of A+BE analyses the structural design of cylindrical Fusée Céramique roofs in the context of those days. The effect of the céramique infill elements for the time dependent deformations, stiffness and load bearing capacity, including second order, is studied. To save the few remaining buildings for the coming generations the possibilities to strengthen these structures with slender light elements of steel are explored. The effect of the strengthening is described for a Fusée Céramique vault, designed and constructed in the past.@en