Deflection limitation of concrete members with non-metallic reinforcement

In non-metallic reinforced concrete members subject to bending the limitation of deflection at the serviceability limit state (SLS) is often decisive. Consequently, the full potential of this innovative construction method in terms of structural capacity remains untapped. In addition, the current version of the DAfStb-Guideline “Concrete members with non-metallic reinforcement” only provides for a simplified approach to determine the deflection. Therefore, the planner is required to employ more sophisticated methodologies, such as the moment-curvature relationship or the finite element method, which are considerably more demanding in terms of complexity and necessitate a detailed understanding of the individualistic material behaviour. In addition, when a long-term or cyclical load is considered, it is crucial to be able to estimate this loading scenario with a high degree of accuracy. Moreover, an explicit consideration of the application case of the combination of bars with grid reinforcement and the extent to which this enables a more targeted assurance of deformation limitation has yet to be undertaken.

To address these issues, experimental investigations were conducted on bending members (slabs and rectangular beams) with different types of reinforcement under cyclic loading at a service load level. The utilisation of fibre optic measurement technology applied to the reinforcement enables a more comprehensive analysis, including the stress redistribution between the reinforcement layers and types. This results in potential optimisations with regard to design as well as the ability to determine the deformation more explicitly, in extension of the guideline.