Influence of microstructure and residual stresses on the fatigue behaviour of ribbed rebar rods
Final Report Abstract
The development of modern reinforcing bars was significantly driven in the 1960s and 1970s. This included the introduction of different surface geometries, such as sickle-shaped transversal ribs. The introduction of these geometries resulted in a reduction of the service life of reinforcing steel bars in fatigue tests. At the same time, the scatter of the test results increased. A comprehensive analysis of the relationships between fatigue behavior, manufacturing process, microstructure, residual stresses, and surface geometry has not yet been conducted. This gap should be filled by the proposed research project. The results of the research project clearly show that the presence of ribs on the surface of the reinforcing steel bars leads to high levels of stress concentration, which results in fatigue cracks occurring at the locations with the highest stress concentrations. The tensile stresses are caused by both the macroscopic geometry of the transversal rib and the microscopic geometry of the surface. The results clearly indicate that the service life of reinforcing steel is reduced by tensile residual stresses caused by the manufacturing process at the point where the ribs are located. Variations in the service life can be attributed to micro and macroscopic geometric variations in the reinforcing steel bar surface and also by changes in the residual stress state.
Publications
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Prediction of process induced microstructure evolution, transformation plasticity and residual stresses in steel reinforcing bars, MSE Conference, Germany, 2020.
C.H. Wölfle, C. Krempaszky & E. Werner
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An implicit integration scheme with consistent tangent modulus for Leblond’s model of transformation-induced plasticity in steels. Continuum Mechanics and Thermodynamics, 34(1), 321-340.
Wölfle, Christoph Hubertus; Krempaszky, Christian & Werner, Ewald
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Structure and thermomechanically induced stress concentration in ribbed reinforcing bars. International Conference on Advanced Computational Engineering and Experimenting (ACEX): St. Julian’s, Malta, 2021.
Robl, T.; Wölfle, C.H.; Hameed, M.Z.; Krempaszky, C. & Werner, E.
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Notch stress analysis on reinforcing steel bars using FE-simulations considering surface topography and structure properties. Current Perspectives and New Directions in Mechanics, Modelling and Design of Structural Systems, 219-220. CRC Press.
Rappl, S. & Osterminski, K.
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Mechanical and Surface Geometric Properties of Reinforcing Bars and Their Significance for the Development of Near-Surface Notch Stresses. Mathematics, 11(8), 1910.
Rappl, Stefan; Shahul, Hameed Muhammed Zubair; Krempaszky, Christian & Osterminski, Kai
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Thermoelasto-Plastic Modeling of Structural Steel: A Parameter Study on Residual Stress Concentrations in Ribbed Reinforcing Bars. Advanced Structured Materials, 569-582. Springer Nature Switzerland.
Robl, Tobias; Krempaszky, Christian & Werner, Ewald
