Verification of the Concrete Slab in Timber-Concrete Composite Structures

Timber-concrete composite (TCC) structures consist of timber beams, a concrete slab and shear connectors. Normally, shear connectors provide a flexible bond between the timber beams and the concrete slab resulting in a composite member. Main applications of such structures are TCC slabs, whereas walls and other elements have been executed only in few cases as TCC member. It is well-known that the shear connectors are of high importance for the load-bearing behavior of TCC slabs. Therefore, many research projects have been carried out aiming on the development and optimization of suitable shear connectors. In contrast, there are only few investigations on the required mechanical properties of the concrete slab. At begin, the paper reports the general structure of TCC slabs, the consequences of flexible bond, and legal situation when applying TCC. In the following, typical loading conditions of concrete slabs as part of a TCC structure is considered. In longitudinal direction, that means in parallel to the timber beams, the section of the concrete slab is mainly under compression. The height of the tensile zone is limited to few millimeters or centimeters. Thus, the application of a conventional steel bar or mesh reinforcement is not useful. Because of needed concrete cover it is impossible to arrange the steel reinforcement within the tensile zone. Alternative solutions, e.g., steel fiber reinforced concrete and textile reinforced are more promising. The paper investigates the concrete slab design when using steel fiber reinforced concrete and textile reinforced concrete.