Zum Tragverhalten von Spannbeton-Fertigdecken bei biegeweicher Lagerung

摘要

In structural engineering ceilings affect both the building technique and the economic construction. Using precast prestressed hollow core slabs meets the demands of modern design and construction to a high extent. However, the shear resistance of hollow core slabs is considerably reduced if the slabs are bedded on slender beams or girders instead of rigid walls. According to investigations in Finland stresses in transverse direction of the slabs due to flexible supports may lead to a decrease in shear resistance of up to 60%. The reduction in shear resistance depends on the composite action between the beam and the slabs, the beam deflection and the slabs’ cross section. No generally accepted design model allowing for a standardised and accurate shear design of prestressed hollow core slabs has been established in Europe so far. Further¬more, the differentiation between rigid and flexible supports is often not clear. Uncertainties in the design and open questions regarding the load bearing behaviour on flexible supports in general limit the application of prestressed hollow core slabs. The aim of the present thesis is a thorough analysis of the load bearing behaviour of prestressed hollow core slabs on flexible supports. At first, the state of the art is summarised. Own experimental and numerical investigations on vital parameters affecting the load bearing behaviour are described in the following. The experimental investigations comprise eight full-scale tests on two-span floor systems with flexible supports and accompanying reference tests on single slabs with rigid supports. Continuative three-dimensional nonlinear FE-analyses provide deep insight into the failure mechanism and the influence of the beam’s bending stiffness on the load bearing behaviour. Based on the experimental and numerical results measures to enhance the shear resistance can be evaluated. A database of international tests with prestressed hollow core slabs on flexible supports from literature is generated to develop a realistic design model for shear. After evaluating the data an existing design model from Finland is used to recalculate the existing tests. An own design model is derived in the next step, whereas especially findings regarding the slabs’ load bearing behaviour and their composite action with the beam at the ultimate limit state are considered. Based on the results of 21 full-scale tests with different types of beams and slabs as well as a parametric study the own model is validated. It accounts for all important factors affecting the load bearing behaviour and hence contributes to an accurate and safe design of prestressed hollow core slabs on flexible supports.