Lightweight ceiling structures made of layered high-perfomance concrete

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The aim of the requested extension period is the exploration of the load bearing behaviour of form optimized layered two-way slabs. Due to the stratification of the cross-section, the materials can be arranged according to the existing stress distribution along the cross-section height. Consequently, each of the applied materials can be put to its best possible use. The high compression and tensile stresses at the top and bottom layer of the sandwich structure are carried by thin layers of suitable concrete or by a reinforcement. In the centre of the cross section, which is under less stress, the load transfer can be achieved through special lightweight concretes. These concretes join the top and bottom layer shear rigid. Through an additional form optimization of the bottom layer according to the principle form follows force, the efficiency of the layered slab can be further increased.Fundamental research carried out in the first funding period served to show that slabs with a layered cross section have a significantly lower self-weight than conventional slabs. The main focus of the work was on choosing an ideal material combination. In particular, the core layers load bearing capacity has to be sufficiently high to guarantee the shear rigid connection of the top and bottom layer (without shear reinforcement). In experimental investigations of one-way slabs, the load bearing behaviour of layered slab elements was analysed and the transition zones between the different failure modes were determined. In the requested project period these fundamental findings are to be transferred to two-way slabs. Furthermore, the influence of layered cross-sections on the biaxial load-transfer is to be determined. Toward this aim, two-way slabs will be numerically and experimentally investigated. The mutual verification of experiment and numerical model will be carried out continually. Subsequently, a force flow optimized two-way slab will be developed. An engineering model and a construction recommendation will be provided for the design of form optimized layered slabs. Finally, the insights gained will be transferred to multi-span systems. Based on the results from project Cross Sectional Adaption for Rod-Shaped Elements, which an extension period has also been applied for, a demonstrator will be developed to prove that the form optimized members can be consolidated in one spatial structure.