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The static design of reinforced concrete slabs is mainly based on finite element calculations. Ever tighter construction schedules and cost pressure on construction sites ultimately mean that the ceiling support times specified in the static calculation can no longer be met. On site, after the early stripping of the ceilings, temporary ceiling underlays will be provided in order to comply with the underlay time. The same scaffolding uprights are used here as for the production of the ceiling. This usual procedure is not examined in the context of the static calculation of the floor ceiling.
In addition, the dimensioning of the reinforced concrete slabs is carried out taking into account the cracked condition state. The latter, however, is undesirable in classic residential buildings, where ceiling soffits are painted white as standard. In addition, climatic conditions and the construction phases are not taken into account in the calculations. This leads to problems with the subsequent finishing trades, for example with the façade assembly or the installation of the floor covering. In order to investigate real ceiling deformations, a research project was carried out in cooperation between the Vienna University of Technology and PORR Bau GmbH [1]. The aim was to determine the deformations of ceilings, taking into account formwork and scaffolding uprights. For this reason, during the construction of a residential complex in Vienna's 10th district, deformation measurements of the different ceilings were carried out from the day of construction to the installation of the floor structure.
In this contribution, the empirically determined load approach [2] for finite element calculations is extended, in which different formwork support times of the floor ceilings were carried out, whereby the focus is on the multi-storey support of slabs that have not reached the full elastic modulus. The research project is intended to help prevent damage and to optimize the construction processes and the time required for the subsequent expansion work.
[1] S. Filipas: Experimental Validation of an Innovative Method for Reducing the Formwork Support Time of Reinforced Concrete Slabs, Master Thesis, Vienna University of Technology, 2025, in German.
[2] H.W. Müllner, S. Akyol, P. Hofer: Experimental Validation of an Innovative Method for Minimization of Deformation Tolerances of Reinforced Concrete Ceilings; PAMM, 24 (2024), https://doi.org/10.1002/pamm.202400036.
