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

Lanwer, Jan-Paul; Empelmann, Martin

doi:10.3390/app11209377

Cited by 7 publications

(12 citation statements)

References 12 publications

(17 reference statements)

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“…The high-strength micro steel fibre is 13.0 mm in length and 0.19 mm in diameter. That gives a slenderness ratio according to Equation (1). The tensile strength is more than 2000 N/mm 2 and the Young's modulus around 200,000 N/mm 2 , according to the manufacturer's data.…”

Section: High-strength Micro Steel Fibre Test Specimen and Test Progr...mentioning

confidence: 89%

“…The intended softening respectively ductile material behaviour of fibre concretes can only be achieved, if the tested fibre design leads to fibre pullout instead of fibre rupture [1,2]. Therefore, the fibres have to match to the strength properties of the concrete.…”

Section: State Of the Art Of Fibre Designmentioning

confidence: 99%

“…Refs. [1,16,17,19] contain detailed information of the test specimen configuration, fabrication, and execution of the pullout tests.…”

Section: High-strength Micro Steel Fibre Test Specimen and Test Progr...mentioning

confidence: 99%

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Performance-Based Fibre Design for Ultra-High Performance Concrete (UHPC)

Lanwer

Empelmann

2022

Applied Sciences

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The paper presents a method to establish a performance-based fibre design of high-strength micro steel fibres for ultra-high-performance concrete (UHPC). The performance-based fibre design considers effects of fibre layout, fibre orientation, and type of loading (quasi-static and cyclic) and expands the current approach using experiences and suitability testing results. The performance-based fibre design is based on a so-called utilization rate, which is determined via pullout tests of high-strength micro steel fibres in UHPC under quasi-static as well as high cyclic loading with varying orientations and embedment depths. The utilization rate for a straight fibre pullout is 0.27 on average considering the measured tensile strength of the fibre and 0.50 considering the manufacturers specifications. For inclined fibres, additional bending stresses occur at the exit point of the fibre channels, leading to a significant increase in local tensile stress. Therefore, the utilization rate of inclined fibres under quasi-static loading is approximately 60–70% higher than in the case of straight embedded fibres (comparing it to the measured tensile strength). Comparing the utilization rate to the manufacturer’s specification, it increases to approximately 1.00. Under cyclic loading, the additional bending stresses in inclined fibres result in a local increase of the load amplitude, leading to a reduced fatigue resistance and premature fibre rupture, underlining the feasibility of a performance-based fibre design.

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Section: High-strength Micro Steel Fibre Test Specimen and Test Progr...mentioning

confidence: 89%

Section: State Of the Art Of Fibre Designmentioning

confidence: 99%

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Performance-Based Fibre Design for Ultra-High Performance Concrete (UHPC)

Lanwer

Empelmann

2022

Applied Sciences

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“…The observations during the test execution showed that there are two failure mechanisms for pullout tests under cyclic tensile loading: Fibre pullout and fibre rupture [ 25 ]. These two failure mechanisms depend on the orientation of the fibres.…”

Section: Experimental Investigationsmentioning

confidence: 99%

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

et al. 2021

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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.

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“…In literature, steel fibre reinforced concrete is usually investigated in uniaxial compression and tensile tests, e.g. [12,13], as well as in flexural tests, e.g. [9,14], with regard to the secondary creep rate.…”

Section: Introduction and State Of The Artmentioning

confidence: 99%

Predictive Power Of Crack Opening Rate For Flexural Fatigue Life Of Steel Fiber-Reinforced High And Ultra-High Performance Concrete

Gebuhr,

Mena-Alonso,

Pise

et al. 2023

Proceedings of the 11th International Conference on Fracture Mechanics of Concrete and Concrete Structures

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Numerical modelling of deterioration in high-cycle fatigue is limited primarily by the computational time required to explicitly calculate large numbers of load cycles on a specific system. Therefore, the aim of this work is to develop an experimentally driven approach to predict the damage evolution of notched 3-point bending beams specimens made of fibre-reinforced high-and ultra-highperformance concrete (HPC/UHPC), which can be used to limit the necessity of extensive numerical calculations of such tests. One possible application is cycle-jump approaches, which aim to avoid the explicit calculation of a large part of the load cycles up to the fatigue failure of the system in the numerical calculations -without having to accept significant losses in the predictive capability of the model. In this contribution, the predictive capability of the crack mouth opening displacement rate ∆CMOD per load-cycle in the second phase of fatigue onto the overall fatigue damage progression is characterised for flexural beams. In this case, this is not explicitly linked only to final failure of the structure. The outlined approach can also be used to estimate the number of cycles until a specifically defined CMOD is reached. This can be important, for example, if crack widths may not be exceeded in cyclically loaded structures. In addition to reference specimens of extremely brittle UHPC and HPC without fibres, the test program consists of specimens with fibre contents of 0.75 % and 1.5 % by volume, which show strain-hardening behaviour. I.e., in preliminary tests, the bending tensile strength was only reached after the proportional limit was reached. The experimental programme includes numerous fatigue tests with constant lower and upper load levels as well as multi-level tests in which one or both load levels were gradually shifted in a block-wise manner. For each block, the cyclic loading was applied long enough to reach the second, linear phase of fatigue deterioration. Overall, it is shown that the secondary creep rate in terms of crack mouth opening provides a valid basis for predicting the failure time (or reaching a given CMOD), despite the well-known scatter of fatigue test series. In a brief outlook, the applicability of a similar use of the stiffness development of the test specimens as a means of prognosis is additionally discussed.

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

Cited by 7 publications

References 12 publications

Performance-Based Fibre Design for Ultra-High Performance Concrete (UHPC)

Performance-Based Fibre Design for Ultra-High Performance Concrete (UHPC)

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

Predictive Power Of Crack Opening Rate For Flexural Fatigue Life Of Steel Fiber-Reinforced High And Ultra-High Performance Concrete

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