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CONCRETE TECHNOLOGYwww.cpi-worldwide.com CPI %u2013 Concrete Plant International %u2013 1 | 2026Four-point bending tests on unnotched beams allow analysis of the constant moment region and the behaviour associated with multiple cracking. In this approach, crack formation between the load application points is treated as a smeared cracking process. This enables a more accurate characterization of strain-hardening behaviour compared with tests on notched beams. However, characterizing the stress-crack opening relationship in strain-hardening materials after the onset of softening presents additional challenges. A methodology addressing this issue is presented in [9].The tensile load-bearing behaviour beyond the proportionality limit cannot be directly determined from flexural tests due to the interaction with compressive stresses. As crack height increases, strain gradients continuously evolve, accompanied by ongoing stress redistribution. Consequently, a direct abstraction of a stress-strain relationship for centric tension is not straightforward. Reliable derivation of the tensile stressstrain relationship from flexural behaviour therefore requires specific algorithms [10 - 12], which can be classified into two categories:The stress%u2013crack opening approach is adopted in many national and international guidelines. In Germany, four-point bending tests on unnotched specimens (l/b/h = 700/150/150 mm) in accordance with [13] are commonly used, whereas internationally, three-point bending tests on notched beams (l/b/h/hsp = 550/150/150/25 mm) according to [4] are predominantly applied.However, due to the multiple cracking behaviour of highly ductile fibre-reinforced concretes, a stress-strain approach up to the maximum load is more appropriate. All methods aim to reproduce the experimental measurement data using models of varying complexity. The constitutive parameters under uniaxial tensile and compressive loading serve as direct input n David Abouem %u00e0 Tchoyi Jr. completed his studies in Civil Engineering at Bauhaus University Weimar in 2004, graduating with a degree in structural engineering. Following an internship, he joined Adam H%u00f6rnig Baugesellschaft in Aschaffenburg in 2005, where he worked as a construction manager. Between 2006 and 2009, he was employed as a research associate at Bauhaus University Weimar at the Chair of Transportation Engineering. Since 2010, he has been working as a research associate at IAB gGmbH. d.abouem@iab-weimar.den Robert Fetter obtained a degree in Mechanical Engineering at the Technical University of Ilmenau, Germany. Subsequently, he worked as a Research Assistant at the Technical University of Ilmenau for a period of 3 years. From 2007 - 2015, he was Deputy Head of Research / Research Promotion at the Thuringian Ministry of Education, Science and Culture. In 2015, he joined the Carl Zeiss Foundation, where he held the position of Deputy Managing Director until 2020. From 2015 - 2019, he was Deputy Head of Institutional Research at the Thuringian Ministry of Economic Affairs, Science and Digital Society. From 2019 - 2023, he held the position of Division Head for Technology Promotion at the Thuringian Ministry of Economic Affairs, Science and Digital Society. Since January 2024, he has been the Director at IAB %u2013 Institute for Applied Building Research Weimar gGmbH.