Lightweight ceiling structures made of layered high-perfomance concrete

申请延长期的目的是探索形状优化的分层双向板的承载性能。由于横截面的分层，材料可以按照现有的沿横截面高度的应力分布进行排列。因此，每一种应用材料都可以得到最好的利用。夹层结构顶层和底层的高压应力和拉应力由薄层合适的混凝土或钢筋承载。在应力较小的截面中心，可以通过特殊的轻质混凝土来实现荷载传递。这些混凝土结合了顶层和底层的剪切刚性。在第一个资助期开展的基础性研究表明，具有分层横截面的楼板自重明显低于常规楼板，通过对底层的附加形状优化，可以进一步提高层板的效率。这项工作的主要重点是选择理想的材料组合。特别是，核心层的承载能力必须足够高，以保证顶层和底层(无抗剪钢筋)的剪切刚性连接。在单向板的试验研究中，分析了层合板单元的受力性能，并确定了不同破坏模式之间的过渡区。在要求的项目期内，这些基本调查结果将转移到双向板上。此外，还需确定分层截面对双向荷载传递的影响。为实现这一目标，将对双向板进行数值和实验研究。实验和数值模型的相互验证将继续进行。随后，将开发出一种力流优化的双向板。为模板优化叠合板的设计提供了工程模型和施工建议。最后，所获得的见解将被转移到多跨系统中。根据已申请延长期的杆件截面适配工程的结果，开发了一个演示程序，以证明形状优化后的杆件可以加固在一个空间结构中。

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.