For more than 100 years now, the construction material reinforced concrete wrote its success story as general solution for houses, bridges and a variety of other engineering structures. With respect to these possible applications and the associated requirements, the static mode of action was researched and developed continuously over the course of time. In the field of short term loads, which could occur for protective constructions for instance, there is still a need for research of the dynamic behaviour of reinforced concrete. Previously to the present project phase, numerous own preliminary studies founded by the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) were carried out. In the frame of the GRS project 1501438 (Tankaufprall Phase 1A, TU Dresden), first a drop tower facility to perform gravity and compressed air driven impact experiments was developed and built at the Otto Mohr Laboratory (OML). During a subsequent parameter study, the influence of varying drop heights, drop masses, impactor diameters, slab geometries as well as different concrete qualities and reinforcement conditions could be investigated by performing 60 drop experiments. The evaluation was realised by the measured defections as well as the occurred damage, which was assessed with the help of a qualitative damage evaluation. The recalculation of the experiments was realised by a developed two-mass oscillator system.
Following to this state of knowledge, in the frame of the GRS project 1501479 (Phase 1B, TU Dresden) further more in depth evaluation was carried out also with regard to the additionally developed theoretical basis for scalability. The work on the existing mass oscillator system was also continued and extended to an approach based on a three-mass oscillator. In addition to the realisation of small-scale experiments to determine the material parameters necessary for the modelling, it was also possible to carry out further impact tests using the accelerated configuration of the drop tower facility. In the frame of 19 experiments, the influence of the impact velocity, the impactor length and its tip shape as well as the concrete quality were investigated under an intensified use of measurement technology. To evaluate the occurred slab damage, extended knowledge was developed together with the Bundesanstalt für Materialforschung und -prüfung (BAM, GRS project 1501477).
Up to this point, both free-fall and accelerated impact tests were carried out in summary. In these tests, it was possible to investigate the influence of external test parameters with regard to the plate deflection and to qualitatively classify the occurred damage. For a more profound understanding of the load-bearing and deformation behaviour of reinforced concrete slabs under impact loading, it was also necessary to pay more attention to the variation of internal parameters. The damage of the reinforced concrete slab, caused by impact, should not only be included in a qualitative way to the overall analysis. Based on the described initial situation, the present report was written as a conclusion of the project Behaviour of structural components during impact load conditions caused by tank collisions (aircraft fuel tanks) - Phase 1C: Experimental and numerical study of scale effects and damage behaviour (GRS 1501541).
The main focus of the performed investigations was on external plate dimensions and on internal parameters such as reinforcement diameter resp. spacing as well as different stirrup reinforcement variants which influence was insufficiently investigated and could not be clearly described to date. From this point of view, the effects of different scaling factors were analysed too. In order to be able to capture the entire interactions and influences, a large number of impact tests were necessary within the framework of a meaningful test grid, which ensured a systematic experimental investigation. Due to this fact, in total 102 accelerated impact tests were carried out and the occurred damage was evaluated by penetration tests without additional pressure as well as on the basis of measureable parameters. At the same time, further investigations regarding the damage assessment were carried out at BAM (GRS project 1501542), which are available in a separate report.
To analyse all influencing variables and their effects, in-depth numerical investigations were carried out in addition to the experimental ones, for the first time. Therewith it was possible to simulate impact tests in detail, which ensures an optimal planning of the experimental investigations on one hand and a better understanding of the resulting observations on the other hand. In addition, for example the influence of liquid-filled or hollow body impactors could also be investigated through the numerics. In connection with the experimental findings, this form the basis of the large-scale tests with combined impact and fire loading planned in project phase 2.