Retrofitting of Timber Beam Ceilings with the Timber-Concrete Composite Construction

Regarding the redevelopment of existing residential buildings the timber-concrete-composite (TCC) construction is an innovative possibility to toughen up timber beam ceilings. Thereby a concrete slab is added to the timber beams. Both parts of the construction are connected by using special shear connectors. In this case timber is mainly loaded in tension and concrete is generally loaded in compression. The bearing capacity as well as the serviceability of the ceiling can be improved by this composite construction. The idea of combining the construction materials timber and concrete in the way that they both can take and carry on loads is not new. In Germany it was mentioned in 1939 for the first time. The cityscape of Central European towns is mainly characterized by buildings constructed before the 50(th) of the last century. The protection of the historical main structure of these buildings is getting more important today. Floors built up till that time were primarily made of timber. Research in Germany has been intensified during the last decade. This paper will show the specific properties of timber-concrete composite floors. Several metallic combing agents exist currently. Type and distance of the connection members influence the load bearing behavior of the composite construction. The main types used in Germany will be presented in this paper. The possible ways of calculating timber-concrete composite ceilings will be given and the design basis will be explained.