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Abstract :
[en] Due to the demand for slim constructions and improvement of erection methods on building site composite slim-floor systems become more important. In the present european and national codes do not include complete design rules for slim-floor constructions. Therefore the objective of this thesis is concentrated on the development of design rules for slim-floor girders.
During the erection stage the elastic design resistance of the steel girder is decisive. Because of the slight plate thickness and sometimes considerable torsional stressing the influence of the shape deformation becomes more important and has to be considered. In this approach the steel sections are filled with concrete in the final state. Thereby the concrete in the openings, arranged in the web or upper flange, work concurrently as concrete dowels. The determination of moment resistance follows the rules for composite structures, respectively whereas in many cases the strain limited design is relevant and additionally the influences from transverse bending in the bottom flange have to be considered. Because of the sheathing of the concrete encasement by the steel section a hybrid truss model with a compression strut in the concrete section is developed, increasing the shear of the section.
In case of fire, the directly flamed bottom flange can be substituted by longitudinal reinforcement bars and a high fire resistance period can be realized without any additional activities. For the analysis in case of fire, a design-method is extracted according to EN 1994-1-2. Based on a transient analysis, thermal analytic functions are developed to describe the temperature distribution in the cross section.
The crack behaviour of the concrete slab has already a significant impact on the girder deformation in the serviceability limit state. The concrete flange adopts a remarkable part of the bending-moment. Compared to general treatment of common composite girders, the neglecting of these bending influences can lead to unrealistic camber of the girder. Therefore, an approximation procedure is derived that considers the bearing of the resilience of composite connector and the crack behaviour on the structure deformation.