Bond behavior of micro steel fibers embedded in ultra‐high performance concrete subjected to monotonic and cyclic loading

Lanwer, Jan-Paul; Oettel, Vincent; Empelmann, Martin; Höper, Svenja; Kowalsky, Ursula; Dinkler, Dieter

doi:10.1002/suco.201900030

Cited by 28 publications

(27 citation statements)

References 15 publications

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“…The focus of this study was the analysis and quantification of the bond behaviour of metallic micro fibres and a cementitious matrix. The simultaneous pullout of five fibres using a CTS device proved to be a suitable method for this purpose as the results are in good agreement with the typical bond-stress curve in the literature [29]. Compared to single-fibre tests [20], the results were found to be more precise and characterised by less scatter, respectively.…”

Section: Discussionsupporting

confidence: 68%

Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC

et al. 2020

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The use of micro fibres in Ultra-High-Performance Concrete (UHPC) as reinforcement increases tensile strength and especially improves the post-cracking behaviour. Without using fibres, the dense structure of the concrete matrix results in a brittle failure upon loading. To counteract this behaviour by fibre reinforcement, an optimal bond between fibre and cementitious matrix is essential. For the composite properties not only the initial surfaces of the materials are important, but also the bonding characteristics at the interfacial transition zone (ITZ), which changes upon the joining of both materials. These changes are mainly induced by the bond of cementitious phases on the fibre. In the present work, three fibre types were used: steel fibres with brass coating, stainless-steel fibres as well as nickel-titanium shape memory alloys (SMA). SMA fibres have the ability of “remembering” an imprinted shape (referred to as shape memory effect), triggered by thermal activation or stress, principally providing for superior performance of the fibre-reinforced UHPC. However, previous studies have shown that NiTi-fibres have a much lower bond strength to the concrete matrix than steel fibres, eventually leading to a deterioration of the mechanical properties of the composite. Accordingly, the bond between both materials has to be improved. A possible strategy is to roughen the fibre surfaces to varying degrees by laser treatment. As a result, it can be shown that laser treated fibres are characterised by improved bonding behaviour. In order to determine the bond strength of straight, smooth fibres of different metal alloy compositions, the present study characterized multiple fibres in series with a Compact-Tension-Shear (CTS) device. For critical evaluation, results obtained by these tests are compared with the results of conventional testing procedures, i.e., bending tests employing concrete prisms with fibre reinforcements. The bond behaviour is compared with the results of the flexural strength of prisms (4 × 4 × 16 cm3) with fibre reinforcements.

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Section: Discussionsupporting

confidence: 68%

Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC

et al. 2020

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“…The additional damage might be responsible for the lesser fatigue resistance of the steel fibres. Nevertheless, the test results and the number of load cycles lie within the usual scatter range for fatigue tests [17,18].…”

Section: Cyclic Loadingmentioning

confidence: 56%

“…The test specimens VM (fibre-group-pullout-tests, Figure 7) consisted of two plain UHPC cubes with nine oriented fibres located in between [15][16][17]. The concrete age of all tests was at least 28 days and the cylinder compressive strength reached more than 150 N/mm 2 .…”

Section: Test Specimen and Test Programmementioning

confidence: 99%

Fundamental Investigations on the Performance of Micro Steel Fibres in Ultra-High-Performance Concrete under Monotonic and Cyclic Tensile Loading

Lanwer

Empelmann

2021

Applied Sciences

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: Ultra-high-performance fibre-reinforced concrete (UHPFRC) can preferably be used for lean and thin-walled structures due to its very high compressive strength. Based on the adverse relation between the increased load bearing capacities and the condensed dead weight of UHPFRC-structures, the impact of live loads in the design gets bigger and, in case of traffic loads, the effects of a cyclic loading have to be considered in more detail. In this context, this study investigated the material behaviour of UHPFRC, especially the tensile fatigue behaviour of high-strength micro steel fibres and the bond behaviour between those fibres and plain UHPC. The test programme included once tensile tests of high-strength micro steel fibres under monotonic and cyclic loading. Based on the test results, an S/N-curve was set up with the characteristic values. Furthermore, the test programme included pullout tests of fibre groups with different embedded lengths and orientations under monotonic and cyclic loading. It was observed that some fibres rupture under certain test configurations like the angle of orientation and the load amplitude.

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“…B. die Einbeziehung hochfester Betone, vorgespannte Bauteile und weit höhere Faserklassen sein. Aktuell laufende Forschungsprojekte beschäftigen sich unter anderem mit dem Durchstanzen bei Kombinationsbewehrung [14], der Nutzung von Mikrofasern und Fasercocktails [15–17], dem Einsatz von Fasern in ultrahochfesten Betonen [18–19], der Teilflächenpressung und Hybridbewehrung [20–22] oder der Nutzung extrem hoher, sogenannter überkritischer Fasergehalte [23, 24], die z. B. übliche kreuzweise Oberflächenbewehrungen ersetzen können.…”

Section: Schlussfolgerungen Und Ausblickunclassified

Neuauflage DAfStb‐Richtlinie Stahlfaserbeton

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et al. 2020

Beton und Stahlbetonbau

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Die Richtlinie „Stahlfaserbeton“ des Deutschen Ausschusses für Stahlbeton (DAfStb) ergänzt DIN EN 1992‐1‐1 mit spezifischen Bemessungsregelungen für Stahlfaserbeton. Sie ist seit 2012 bauaufsichtlich eingeführt – besitzt also normativen Charakter – und wurde nun in zwei Punkten wesentlich überarbeitet bzw. ergänzt. Zum einen wurden Regelungen für die Torsionsbemessung aufgenommen. Solche fehlten bislang aufgrund mangelnder Erfahrungen. Zum anderen wurden die Vorschriften zur Rissbreitenbeschränkung angepasst. Hier wurde die Nutzung des sogenannten L1‐Werts, der das Zugtragverhalten des Stahlfaserbetons bei kleinen Rissbreiten beschreibt, eingeführt. Bislang wurde konservativ mit dem sogenannten L2‐Wert gerechnet. Der Beitrag beschreibt die Überarbeitungen und erläutert kurz die Hintergründe dazu.

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Bond behavior of micro steel fibers embedded in ultra‐high performance concrete subjected to monotonic and cyclic loading

Cited by 28 publications

References 15 publications

Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC

Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC

Fundamental Investigations on the Performance of Micro Steel Fibres in Ultra-High-Performance Concrete under Monotonic and Cyclic Tensile Loading

Neuauflage DAfStb‐Richtlinie Stahlfaserbeton

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