Experiments on Symmetrically Reduced Reinforced Concrete Beams

Abstract

As the competition on realizing larger, thicker and more wide-spanned structural reinforced concrete members continues, questions arise concerning the safety and economic quality of these large structural members implying significant size effects. Due to limitations concerning the experimental infrastructure and due to economic reasons resulting from outstanding time- and material-consuming efforts, there is a remarkable lack of experimental results especially concerning reinforced concrete members with large effective depths. At the Institute of Concrete Structures at the Ruhr-Universitat Bochum, an innovative experimental test setup is developed to enable the multiply requested size effect investigations of larger reinforced concrete members. It focuses on utilizing the symmetry conditions of loading and test members, comparable to the best practice of the discretization procedure in numerical investigations. Thus, beams are halved and slabs quartered. Proportional to the symmetry grade test loads and dead loads pronouncedly decrease giving rise to larger specimen within given testing facilities. Initially designed and configured for testing the punching shear failure of thick reinforced concrete slabs, the setup also enables tests on symmetrically sectioned concrete members like single-span beams loaded in bending or shear. The contribution presents the single steps of the development to test symmetrically bisected reinforced concrete beams, including the modular bearing constructions with sliding planes and back anchorings of the bending reinforcement as well as the concrete specimen itself with interconnections to the symmetry planes, measuring techniques and its specific assembly. The comparison of the results of verification tests on halved beams and corresponding full-size members shows a remarkable accordance and proofs the general applicability in failure modes, crack pattern, yielding and failure loads.