A5/II Strengthening on the rear side of flat, stirrup reinforced solid construction elements against impact

Doctoral Researcher
Franz Bracklow

Principal Investigator
Manfred Curbach

Participating Investigator
Birgit Beckmann

in cooperation with 
Michael Kaliske

Project poster
Download PDF

The impact resistance of reinforced concrete slabs can be increased by layers of thin mineral-bonded matrices with embedded fibre based fabrics. To fully prove the potential of the developed strengthening concepts investigations and optimizations are necessary. Of interest is, for example, how the effectiveness of the strengthening measure depends on the design of the basic component. Especially the aspect of the presence of stirrup reinforcement which influences the punching angle is essential. The activation of the reinforcement in the strengthening layer also requires in-depth consideration. Engineering models developed so far do not sufficiently represent the load-bearing behaviour and must be improved.

Bottom side of steel reinforced concrete slabs after impact tests (same impact speeds); from left to right: non-strengthened, with subsequent strengthening made of SHCC and SHCC with carbon fiber fabric
© M. Hering

Left to right: Structure and sensor development for reinforcing elements that are based on continuous fibers and suitable for impact scenarios; impact testing technology

Stirrup-reinforced slabs are often used in reinforced concrete structures exposed to higher loads, such as bridges or rockfall galleries. Although it is known that stirrup reinforcement influences the stress and deformation state, but also crack development (including the shape and expansion of a punching cone), this stirrup effect has been neglected in the past in impact tests with reinforced plates and in engineering models. This should be investigated in order to obtain a complete understanding of the effect and performance of strengthening layers on the rear side of impacted components. The quantitative damage description must be extended by the stirrup effect and the engineering model must be validated accordingly. The interaction of reinforcement fabrics and fibre concrete matrices must also be intensified. Accompanying numerical investigations at macro level can significantly improve the understanding of the effects occurring during the impact process and support the evaluation of the experiments.