Reinforcements of concrete structures in construction usually occurs with internal reinforcements. However, they only increase the absorption of tensile forces, but cannot improve the strength of the concrete itself. Thus, the use of stronger and costly concrete is necessary. New possibilities arise by the use of a fibre reinforced hollow structure as external reinforcement and at once as formwork for the concrete filling. This way higher design freedom is provided regarding the use of fibre reinforced plastic (FRP)-concretes for individual components and simultaneously– in contrast to internal reinforcements – also the compressive strength of the concrete increases by the external compressive effect of the FRP hull. Ensuring the form closure between hull and concrete in the interfacial area is critical in this manufacturing approach due to the pictured transfer of forces.
By the hardening of the concrete, the shrinkage creates a micro-gap between FRP and concrete. It can be bridged for example by structuring the inner FRP surface. For planar components, this approach can be implemented very well, i.e. by inserting a fibre grid. For convex-concave curved geometries this is due to the poor drapability of grids associated with complex pre-cutting.
Based on a well known textile technology a process has been developed for complex curved geometries: Textile connection elements bridging micro-gaps between concrete core and FRP hull. In scientific investigations, the general adhesion properties between FRP with connection elements and concrete as well as the influencing variables of the textile process with regard to their effects on mechanical parameters were investigated. Decisive influencing factors result both from the textile process as well as the component design. The mechanical examination proves that the adhesion between concrete and FRP is significantly increased, consequently the form closure is given and a force transfer is ensured in the envisaged application.