Determination of fracture parameter and prediction of structural fracture using various concrete specimen types

Guan, Junfeng; Liu, Changming; Wang, Juan; Qing, Longbang; Song, Zeng; Liu, Zenpeng

doi:10.1016/j.tafmec.2019.01.008

Cited by 57 publications

(19 citation statements)

References 37 publications

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“…It can be concluded that the value of β is 1.0-1.4, and reasonable tensile strength f t and fracture toughness K IC can be obtained for small aggregate fracture specimens. The results agree well with those of [53], which were reached based on concrete fracture experiments with various specimen types. In conclusion, the model can be used to simulate the fracture tests of small size concrete under different conditions.…”

Section: Discussion Of the Size Effect On Fracture Toughness And Tenssupporting

confidence: 89%

“…It is agreed that the fracture toughness will not increase when the specimen's size is large enough [49,50]. Compared with the other classic size effect law [5,6,8,9], the boundary effect model [51][52][53][54][55] needs less input data (only peak load P max ) to determine the size-independent tensile strength f t and fracture toughness K IC , shown as Equation (9), which is a more suitable application for the numerical model. The peak loads (P max ) obtained from the above numerical model, the experiments of [30] and the parameters involved can be used with this equation to determine the tensile strength of concrete specimens.…”

Section: Discussion Of the Size Effect On Fracture Toughness And Tensmentioning

confidence: 99%

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Numerical Simulation on Size Effect of Fracture Toughness of Concrete Based on Mesomechanics

Wang

Guan

et al. 2020

Materials

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The fracture performance of concrete is size-dependent within a certain size range. A four-phase composite material numerical model of mesofracture considering a mortar matrix, coarse aggregates, an interfacial transition zone (ITZ) at the meso level and the initial defects of concrete was established. The initial defects were assumed to be distributed randomly in the ITZ of concrete. The numerical model of concrete mesofracture was established to simulate the fracture process of wedge splitting (WS) concrete specimens with widths of 200-2000 mm and three-point bending (3-p-b) concrete specimens with heights of 200-800 mm. The fracture process of concrete was simulated, and the peak load (P max ) of concrete was predicted using the numerical model. Based on the simulating results, the influence of specimen size of WS and 3-p-b tests on the fracture parameters was analyzed. It was demonstrated that when the specimen size was large enough, the fracture toughness (K IC ) value obtained by the linear elastic fracture mechanics formula was independent of the specimen size. Meanwhile, the improved boundary effect model (BEM) was employed to study the tensile strength (f t ) and fracture toughness of concrete using the mesofracture numerical model. A discrete value of β = 1.0-1.4 was a sufficient approximation to determine the f t and K IC values of concrete.Materials 2020, 13, 1370 2 of 16 considered that when the height of the specimen reaches 800 mm, the measured fracture toughness K IC value no longer has size effects [4]. The similar conclusion drawn by Bazant [5] is that the mechanical parameters measured for specimens in a certain size range had size effects. That is to say, when the size of the specimens was small enough or large enough, the mechanical properties and fracture parameters remained unchanged. In view of this experimental phenomenon, Weibull [8,9] considered that the size dependence was due to the increase in the probability of encountering low-strength material elements with increasing structure sizes. Based on the law of extreme strength distribution, a size effect statistical theory was proposed. However, this theory was limited to structures that fail at the beginning of macro-cracks and small structures that only cause negligible stress redistribution in the fracture process zone when they fail. Subsequently, based on the energy theory, Bazant et al. [5] proposed a size effect theory of fracture mechanics for geometrically similar specimens with a size range of approximately 1:20 notches. Based on the concept of fractals, Carpinteri et al.[6] established a multi-fractal size effect law that reflected the unstable cracking of structures when the size range was approximately 1:10. Hu [7] concluded that the initial crack and ligament depth should be far from the specimen boundary to reflect the true mechanical parameters of a material, independent of size. Based on this, the boundary effect theory was established. In addition to this basic theory, indirect size effects such as the boundary layer ...

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Section: Discussion Of the Size Effect On Fracture Toughness And Tenssupporting

confidence: 89%

Section: Discussion Of the Size Effect On Fracture Toughness And Tensmentioning

confidence: 99%

Numerical Simulation on Size Effect of Fracture Toughness of Concrete Based on Mesomechanics

Wang

Guan

et al. 2020

Materials

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“…During the entire bending test, no crack forms at the first stage where crack propagation is linear elastic. Then, a crack is under elastoplastic propagation until the fracture load [40][41][42]. The crack initiation load (F Q ) is the load at the breakpoint from linear to nonlinear in the curve of load-CMOD.…”

Section: Fracture Propertiesmentioning

confidence: 99%

Effects of nanoparticles on engineering performance of cementitious composites reinforced with PVA fibers

Ling

Zhang

Wang

et al. 2020

Nanotechnology Reviews

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AbstractIn this study, the influence of nano-CaCO3 (NC) and nano-SiO2 (NS) on engineering properties of cementitious composites reinforced with polyvinyl alcohol (PVA) fibers was investigated including slump and fracture properties as well as compressive, flexural, tensile, and strengths. The influence mechanism of NS content on properties of cementitious composites was revealed. The combined effects of NS and NC were evaluated on the composites made with 0.9% volumetric PVA fiber addition. The experimental results showed that the addition of nanoparticles decreased the workability of fresh cementitious composites reinforced with PVA fibers. Higher NS content deceased more workability and NC reduced more workability than NS for the composites. There was an initial increase and later decrease in compressive and flexural strengths as NS content alters from 0% to 2.5%, while the continuous increase was found in tensile strength. 1.5% NS maximally increased compressive strength and flexural strength, while 2.5% NS is optimal for tensile strength. The composite containing NC exhibited lower strengths than the composite containing the same content of NS. The fracture energy, initiation, and unstable fracture toughness slightly increased with the NS content varying from 0% to 1.5%, while they reduced when NS content was higher than 1.5%. The effects of NS and NC on fracture energy and toughness were inapparent. The failure mode of PVA fibers in the tensile strength test was changed from pull-out to fracture with the addition of NS based on microstructure characterization.

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“…The size‐independent tensile strength f t and the fracture toughness K IC of concrete can be determined by the regression analysis of the experimental data via SEM or BEM. Recently, an improved BEM fully considered the effect of the maximum aggregate size of concrete or the particle size of rock on fracture has been proposed 36–43 and used for the analysis of concrete, 36–40 cement mortar, 41 rock 42 and metal 43 . However, this method only focuses on the material parameters of the peak load state (tensile strength f t and fracture toughness K IC ) and does not consider the material parameters of the crack initiation state (

f_{t}^{ini}

and

K_{IC}^{ini}

).…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, in this study, the concept of material parameter and initial cracking strength

f_{t}^{ini}

was elaborated. Based on the previous studies on BEM, 36–43 the methodology of determining the initial cracking strength

f_{t}^{ini}

and the corresponding another material parameter, initial fracture toughness

K_{IC}^{ini}

, was proposed. The design curves of concrete crack initiation were established based on the determined

f_{t}^{ini}

and

K_{IC}^{ini}

.…”

Section: Introductionmentioning

confidence: 99%

Initial cracking strength and initial fracture toughness from three‐point bending and wedge splitting concrete specimens

Yao

Guan

et al. 2020

Fatigue Fract Eng Mat Struct

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In this study, a concept of initial cracking strength of concrete was elaborated. A fracture model and associated methods for determining independent initial cracking strength and initial fracture toughness by the three‐point bending (3‐p‐b) and wedge splitting (WS) concrete specimens are presented. The initial cracking strength and initial fracture toughness can be simultaneously determined using a curve fitting method from the proposed fracture model. All of the initial fracture curves were obtained by the determined concrete materials. The initial loads of the 3‐p‐b and WS specimens were predicted on the basis of the curves with ±15% ranges. Furthermore, the initial cracking strength and the initial fracture toughness of concretes were directly determined by analytical functions. The determined values within ±15% ranges cover most of the initial loads of the 3‐p‐b and WS specimens.

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Determination of fracture parameter and prediction of structural fracture using various concrete specimen types

Cited by 57 publications

References 37 publications

Numerical Simulation on Size Effect of Fracture Toughness of Concrete Based on Mesomechanics

Numerical Simulation on Size Effect of Fracture Toughness of Concrete Based on Mesomechanics

Effects of nanoparticles on engineering performance of cementitious composites reinforced with PVA fibers

Initial cracking strength and initial fracture toughness from three‐point bending and wedge splitting concrete specimens

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