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T. Huber, P. Huber, J. Kollegger:
"Shear Behaviour of Existing RC Structures with a Single Group of Bent-Up Bars as Shear Reinforcement";
Talk: fib Symposium 2021, Portugal; 2021-06-14 - 2021-06-16; in: "Concrete Structures: New Trends for Eco-Efficiency and Performance", fib, (2021), ISBN: 978-2-940643-08-0; 1434 - 1441.

Using bent-up bars as shear reinforcement was state of the art in Europe until the seventies of the last century. Therefore, static recalculations of those structures have become an important task in the daily engineering practice. However, the application of current structural standards often does not allow a positive assessment with respect to the shear capacity, especially if a single group of parallel bent-up bars is constructed. To bring more light into this matter, the results of an extensive experimental program on bent-up longitudinal bars are analysed. It includes nine tests on slab segments with the dimensions of 6.50/0.40/0.55 metres. The investigated parameters were position of the group bent-up bars with a bending angle of 45 degrees and shear slenderness. Through the use of close-range photogrammetry, an evaluation of the crack kinematics of critical shear cracks are conducted. The evaluation gave plausible results considering the experimental loads. It became obvious that the shear force component of the bent-up longitudinal bar can act together with those of the concrete. Besides, the shape and the kinematics of the shear cracks are similar to cracks, as can be expected structures without shear reinforcement. The presented evaluations and observations provide the experimental basis for the development of more realistic models for the assessment of the shear capacity of existing structures.

shear tests, bent-up bars, digital image correlation, shear transfer mechanisms