Punching shear tests on symmetrically reduced slab quarters

Experiments on large-scale reinforced concrete members such as beams or slabs with large effective depths are challenging and - not least due to the extensive material and financial input - rarely performed. However, results from such experiments are desperately needed, as critical size effects affect shear and punching shear failure types. At the Institute of Concrete Structures at Ruhr-Universität Bochum (RUB), an innovative test setup was devised following the principle of “upsizing by downsizing”. It transfers symmetry reductions - a standard feature in numerical simulations - to experiments. Thus, test loads and dead loads decrease markedly in proportion to the degree of symmetry, giving rise to larger specimens within given testing facilities. The setup enables tests on symmetrically sectioned concrete members - halved beams or quarters of slabs - concurrently implying the load-deformation behaviours of corresponding, i.e. full-size members, by simply factoring the loads with twice the axial symmetry degree.
This paper presents the single steps in the development to test quartered slabs, including the modular support constructions with sliding planes and anchoring of the bending reinforcement as well as the concrete specimen itself, with interconnections to the symmetry planes, measuring techniques and its specific assembly. Results from a first prototype testing prove the general applicability for failure modes, crack patterns and kinematics. However, ultimate punching loads are still slightly overestimated.