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Article

Fundamental Investigations of Bond Behaviour of High-Strength Micro Steel Fibres in Ultra-High Performance Concrete under Cyclic Tensile Loading

1
iBMB (Institute of Building Materials, Concrete Construction and Fire Safety), Division of Concrete Construction, Faculty of Architecture, Civil Engineering and Environmental Science, Technische Universität Braunschweig, 38106 Braunschweig, Germany
2
ISD (Institute of Structural Analysis), Faculty of Architecture, Civil Engineering and Environmental Science, Technische Universität Braunschweig, 38106 Braunschweig, Germany
*
Author to whom correspondence should be addressed.
Academic Editors: Karim Benzarti and Csaba Balázsi
Materials 2022, 15(1), 120; https://doi.org/10.3390/ma15010120
Received: 21 October 2021 / Revised: 17 December 2021 / Accepted: 21 December 2021 / Published: 24 December 2021
(This article belongs to the Special Issue Cyclic Deterioration of Concrete)
The objective of the contribution is to understand the fatigue bond behaviour of brass-coated high-strength micro steel fibres embedded in ultra-high performance concrete (UHPC). The study contains experimental pullout tests with variating parameters like load amplitude, fibre orientation, and fibre-embedded length. The test results show that fibres are generally pulled out of the concrete under monotonic loading and rupture partly under cyclic tensile loading. The maximum tensile stress per fibre is approximately 1176 N/mm2, which is approximately one third of the fibre tensile strength (3576 N/mm2). The load-displacement curves under monotonic loading were transformed into a bond stress-slip relationship, which includes the effect of fibre orientation. The highest bond stress occurs for an orientation of 30° by approximately 10 N/mm2. Under cyclic loading, no rupture occurs for fibres with an orientation of 90° within 100,000 load changes. Established S/N-curves of 30°- and 45°-inclined fibres do not show fatigue resistance of more than 1,000,000 load cycles for each tested load amplitude. For the simulation of fibre pullout tests with three-dimensional FEM, a model was developed that describes the local debonding between micro steel fibre and the UHPC-matrix and captures the elastic and inelastic stress-deformation behaviour of the interface using plasticity theory and a damage formulation. The model for the bond zone includes transverse pressure-independent composite mechanisms, such as adhesion and micro-interlocking and transverse pressure-induced static and sliding friction. This allows one to represent the interaction of the coupled structures with the bond zone. The progressive cracking in the contact zone and associated effects on the fibre load-bearing capacity are the decisive factors concerning the failure of the bond zone. With the developed model, it is possible to make detailed statements regarding the stress-deformation state along the fibre length. The fatigue process of the fibre-matrix bond with respect to cyclic loading is presented and analysed in the paper. View Full-Text
Keywords: fatigue; degradation; ultra-high performance fibre-reinforced concrete; tensile loading; bond behaviour; bond zone damage; damage modelling fatigue; degradation; ultra-high performance fibre-reinforced concrete; tensile loading; bond behaviour; bond zone damage; damage modelling
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MDPI and ACS Style

Lanwer, J.-P.; Höper, S.; Gietz, L.; Kowalsky, U.; Empelmann, M.; Dinkler, D. Fundamental Investigations of Bond Behaviour of High-Strength Micro Steel Fibres in Ultra-High Performance Concrete under Cyclic Tensile Loading. Materials 2022, 15, 120. https://doi.org/10.3390/ma15010120

AMA Style

Lanwer J-P, Höper S, Gietz L, Kowalsky U, Empelmann M, Dinkler D. Fundamental Investigations of Bond Behaviour of High-Strength Micro Steel Fibres in Ultra-High Performance Concrete under Cyclic Tensile Loading. Materials. 2022; 15(1):120. https://doi.org/10.3390/ma15010120

Chicago/Turabian Style

Lanwer, Jan-Paul, Svenja Höper, Lena Gietz, Ursula Kowalsky, Martin Empelmann, and Dieter Dinkler. 2022. "Fundamental Investigations of Bond Behaviour of High-Strength Micro Steel Fibres in Ultra-High Performance Concrete under Cyclic Tensile Loading" Materials 15, no. 1: 120. https://doi.org/10.3390/ma15010120

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