Description
The cement factory of the Märker Group extended its quarry facilities in the Donau-Ries district and built a blending bed for crushed raw material. The new facility is to ensure constant proportioning of all components and, therefore, to guarantee a stable cement quality. Since the existing facility of 1968 did not meet the quality standards anymore, and as storage capacity was running short, the company decided in the late 1990s to build a new circular blending bed.
The roof structure looks like an oversize igloo, which above all – apart from preventing the raw material from going moist and lumpy – is supposed to provide noise protection. The structure is composed of 16 arched three-chord steel tube girders freely spanning an area of about 8,000 m². Massive reinforced concrete foundations support the base points of the girders, which at the top are centrally connected by a compression ring from which the rock discharge station at the end of the conveyor belt is suspended as well.
In between each pair of girders run valley cables creating saddle-shaped, double-bent surfaces increasing the load-bearing capacity of the material. The tensioned cables are anchored in gravity foundations in the ground. Reinforcing cables are shrink-wrapped by the bottom edge of the membrane; the edge is bent following the trajectories of stress, thus creating arches with a clear rise of 4 m all around the building. An interior flat steel ring positioned underneath the compression ring receiving the membrane by means of clamps as well as the ridge and valley cables forms the upper connection of the membrane.
The opening of the compression ring at the top is covered by a textile umbrella structure, which is tensioned by props with stretchers. The gap between umbrella and top edge of the membrane provides – in combination with the arched air intakes at the bottom – an effective natural ventilation of the large domed volume.
Drawings
Top view
Floor plan diagram
Elevation
Connection detail of ridge cable and membrane to bottom chord of girder
Connection detail of valley cable to flat steel ring at top
Photos
View of the entire complex including new circular blending bed
Interior view with rock discharge station at the end of the conveyor belt
Originally published in: Jürgen Adam, Katharina Hausmann, Frank Jüttner, Industrial Buildings: A Design Manual, Birkhäuser, 2004.