Influence of sustained loading on fracture properties of concrete

Wei Dong, Xue Zhang, BinSheng Zhang, Qiao Wu

Research output: Contribution to journalArticle

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Abstract

To investigate the effects of sustained loading on the fracture properties of concrete, basic creep and three-point bending (TPB) tests were conducted on the pre-notched beams. The specimens were first subjected to two sustained loading levels, i.e. 30% peak load and the initial cracking load over 115 days. Then, they were moved out from the loading frames and tested under TPB  loading until failure. The critical crack propagation length (¿ac), the peak load (Pmax) and the fracture energy (Gf) were measured in the tests, and the unstable fracture toughness (KICun) was calculated accordingly. Furthermore, based on the load-displacement curves obtained in the TPB tests, the energy dissipation was derived using the modified J-integral method. By enforcing balance between the energy dissipated and the energy caused by the fictitious cohesive force acting on the fracture process zone, the tension-softening constitutive laws under the two sustained loading levels were established and also simplified as bilinear forms for practical applications. Finally, the effects of sustained loading on the fracture properties were examined by comparing with the tested results from the aging specimens in the static TPB tests. The test results indicate that low sustained loading had no effects on all fracture properties of concrete investigated in this study, while under high sustained loading, ¿ac and KICun increased and Gf and Pmax almost remained unchanged. Meanwhile, a smaller free-stress crack opening displacement was obtained under the high sustained loading level, which indicates a shorter FPZ length formed, resulting in the increase in brittleness of concrete.
Original languageEnglish
Pages (from-to)134-145
Number of pages12
JournalEngineering Fracture Mechanics
Volume200
Early online date24 Jul 2018
DOIs
Publication statusPublished - Sep 2018

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Bending tests
Concretes
Fracture energy
Brittleness
Fracture toughness
Crack propagation
Energy dissipation
Creep
Aging of materials
Cracks

Keywords

  • sustained loading, concrete, fracture properties, tension-softening constitutive law

Cite this

Dong, W., Zhang, X., Zhang, B., & Wu, Q. (2018). Influence of sustained loading on fracture properties of concrete. Engineering Fracture Mechanics, 200, 134-145. https://doi.org/10.1016/j.engfracmech.2018.07.034
Dong, Wei ; Zhang, Xue ; Zhang, BinSheng ; Wu, Qiao. / Influence of sustained loading on fracture properties of concrete. In: Engineering Fracture Mechanics. 2018 ; Vol. 200. pp. 134-145.
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Dong, W, Zhang, X, Zhang, B & Wu, Q 2018, 'Influence of sustained loading on fracture properties of concrete', Engineering Fracture Mechanics, vol. 200, pp. 134-145. https://doi.org/10.1016/j.engfracmech.2018.07.034

Influence of sustained loading on fracture properties of concrete. / Dong, Wei; Zhang, Xue; Zhang, BinSheng; Wu, Qiao.

In: Engineering Fracture Mechanics, Vol. 200, 09.2018, p. 134-145.

Research output: Contribution to journalArticle

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AU - Zhang, Xue

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AU - Wu, Qiao

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N2 - To investigate the effects of sustained loading on the fracture properties of concrete, basic creep and three-point bending (TPB) tests were conducted on the pre-notched beams. The specimens were first subjected to two sustained loading levels, i.e. 30% peak load and the initial cracking load over 115 days. Then, they were moved out from the loading frames and tested under TPB  loading until failure. The critical crack propagation length (¿ac), the peak load (Pmax) and the fracture energy (Gf) were measured in the tests, and the unstable fracture toughness (KICun) was calculated accordingly. Furthermore, based on the load-displacement curves obtained in the TPB tests, the energy dissipation was derived using the modified J-integral method. By enforcing balance between the energy dissipated and the energy caused by the fictitious cohesive force acting on the fracture process zone, the tension-softening constitutive laws under the two sustained loading levels were established and also simplified as bilinear forms for practical applications. Finally, the effects of sustained loading on the fracture properties were examined by comparing with the tested results from the aging specimens in the static TPB tests. The test results indicate that low sustained loading had no effects on all fracture properties of concrete investigated in this study, while under high sustained loading, ¿ac and KICun increased and Gf and Pmax almost remained unchanged. Meanwhile, a smaller free-stress crack opening displacement was obtained under the high sustained loading level, which indicates a shorter FPZ length formed, resulting in the increase in brittleness of concrete.

AB - To investigate the effects of sustained loading on the fracture properties of concrete, basic creep and three-point bending (TPB) tests were conducted on the pre-notched beams. The specimens were first subjected to two sustained loading levels, i.e. 30% peak load and the initial cracking load over 115 days. Then, they were moved out from the loading frames and tested under TPB  loading until failure. The critical crack propagation length (¿ac), the peak load (Pmax) and the fracture energy (Gf) were measured in the tests, and the unstable fracture toughness (KICun) was calculated accordingly. Furthermore, based on the load-displacement curves obtained in the TPB tests, the energy dissipation was derived using the modified J-integral method. By enforcing balance between the energy dissipated and the energy caused by the fictitious cohesive force acting on the fracture process zone, the tension-softening constitutive laws under the two sustained loading levels were established and also simplified as bilinear forms for practical applications. Finally, the effects of sustained loading on the fracture properties were examined by comparing with the tested results from the aging specimens in the static TPB tests. The test results indicate that low sustained loading had no effects on all fracture properties of concrete investigated in this study, while under high sustained loading, ¿ac and KICun increased and Gf and Pmax almost remained unchanged. Meanwhile, a smaller free-stress crack opening displacement was obtained under the high sustained loading level, which indicates a shorter FPZ length formed, resulting in the increase in brittleness of concrete.

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