scholarly journals Probabilistic Fracture Energy Assessment of Natural Fibre Reinforced Concrete by Two Parameter Weibull Distribution

2018 ◽  
Vol 7 (3.12) ◽  
pp. 407
Author(s):  
Neha P Asrani ◽  
Murali G ◽  
Arthika J ◽  
Karthikeyan. K ◽  
Haridharan. M.K
Keyword(s):  
Weibull Distribution ◽  
Fracture Energy ◽  
Plain Concrete ◽  
Natural Fibre ◽  
Test Results ◽  
Specific Fracture Energy ◽  
Energy Assessment ◽  
Experimental Process ◽  
Specific Fracture ◽  
Two Parameter

Fracture energy is the post-crack energy absorption ability of the material that represents the energy absorbed by the structure at the time of failure. Its analysis has gained importance and hence requires a powerfulmethod for its development. A two parameter Weibull distribution proves to be an efficient tool in analysing the scattered experimental test results. In this paper, the specific fracture energy of plain concrete and concrete reinforced with natural fibres of hemp, wheat straw and elephant grass are statistically analysed by two parameter Weibull distribution by using graphical method. For determining Weibull parameters, 21 equations have been used and the best equation is taken for the reliability analysis. A Weibull reliability curve is plotted, which shows the specific fracture energy at each reliability level. This curve enables an engineer to choose the fracture energy of a particular mix based on its reliability requirement and safety limit. Therefore, reliability curves are a pioneer in statistical analysis as they eliminate the time-consuming and costly experimental process. This method can be applied in areas with similar uncertainties.  

Boundary Effect on the True Specific Fracture Energy of Concrete

2007 ◽  
Vol 348-349 ◽  
pp. 933-936
Author(s):  
Yan Hua Zhao ◽  
Shi Lang Xu ◽  
Zhi Min Wu ◽  
Hong Bo Gao
Keyword(s):  
Size Effect ◽  
Fracture Energy ◽  
Boundary Effect ◽  
Apparent Size ◽  
Specimen Size ◽  
Test Results ◽  
Bilinear Model ◽  
Local Fracture ◽  
Specific Fracture Energy ◽  
Specific Fracture

The apparent size effect of the specific fracture energy of concrete according to the RILEM procedure has been confirmed by numerous published works. The paper offers an explanation for this size effect by considering the specimen boundary influence on local fracture energy over the ligament length, which is closely associated with the measured fracture energy of concrete. To address this boundary influence, boundary affected length is introduced, over which local fracture energy is different from that in the bulk far away from the surface of the specimen. Based on previous work, a continuous smooth function is hypothesized to simulate the distribution of local fracture energy. At the same time, the model established was compared to the existing models, i.e. Perturbed Ligament Model (PLM) and Bilinear Model (BLM). Some test results from wedge splitting specimen in the literature were used to verify these three models. The results show that the true fracture energy of concrete, irrespective of the specimen size, could be obtained from the measured values directly from RILEM, and is less sensitive to determination approach. The predicted boundary affected length when the crack reaches the specimen surface is more close to the value of the perturbation length in PLM.

Fracture Behaviour of Modified Spruce Wood: A Study Using Linear and Non Linear Fracture Mechanics

Holzforschung ◽  
2002 ◽  
Vol 56 (2) ◽  
pp. 191-198 ◽  
Author(s):  
Alexander Reiterer ◽  
Gerhard Sinn
Keyword(s):  
Fracture Energy ◽  
Heat Treatments ◽  
Critical Stress Intensity Factor ◽  
Mode I ◽  
Mode Iii ◽  
Fracture Properties ◽  
Specific Fracture Energy ◽  
Wedge Splitting Test ◽  
Splitting Test ◽  
Specific Fracture

Summary The fracture properties of unmodified and modified (heat treatments under various conditions and acetylation) sprucewood are investigated using the wedge splitting test. Fracture parameters measured include critical stress intensity factor and specific fracture energy under Mode I loading and specific fracture energy under Mode III loading. The Mode I fracture properties are reduced by all kinds of modification. However, acetylation leads to a reduction of only 20%whereas heat treatments reduce the properties to a much greater extent, approximately 50%to 80%. The Mode III fracture properties are influenced less. SEM pictures of the fracture surfaces support the described findings.

Damage and Fracture Mechanisms during Mode I and III Loading of Wood

Holzforschung ◽  
2001 ◽  
Vol 55 (5) ◽  
pp. 525-533 ◽  
Author(s):  
E.K. Tschegg ◽  
K. Frühmann ◽  
S.E. Stanzl-Tschegg
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Fracture Energy ◽  
Fracture Mechanisms ◽  
Mode I ◽  
Mode Iii ◽  
Initiation Energy ◽  
Specific Fracture Energy ◽  
Damage And Fracture ◽  
Specific Fracture

Summary Tests under mode I and mode III loading were performed on side grooved Compact-Tension specimens of larch and beech under steady state crack propagation to study the damage and fracture behaviour and the influence of two fibre orientations. From the complete load-displacement diagram, all important damage and fracture mechanical values (stiffness/compliance, microstructural damage, crack initiation energy, specific fracture energy, etc.) have been determined. Crack initiation energy and specific fracture energy are approximately ten times higher for mode III loading than for mode I loading in both wood species. Crack initiation occurs in mode III under external mode III loading, crack propagation, however, takes place under mode I, owing to crack surface interference. The influence of fibre orientation on the (fracture) mechanical properties of beech and larch is different. This difference may be explained mainly by the high number of rays in beech.

scholarly journals Dynamic crack propagation in weak snowpack layers: Insights from high-resolution, high-speed photography

2021 ◽  
Author(s):  
Bastian Bergfeld ◽  
Alec van Herwijnen ◽  
Benjamin Reuter ◽  
Grégoire Bobillier ◽  
Jürg Dual ◽  
...  
Keyword(s):  
High Resolution ◽  
Crack Propagation ◽  
Fracture Energy ◽  
High Speed ◽  
Image Correlation ◽  
Crack Speed ◽  
Specific Fracture Energy ◽  
Weak Layer ◽  
Specific Fracture ◽  
Insight Into

Abstract. To assess snow avalanche release probability, information on failure initiation and crack propagation in weak snowpack layers underlying cohesive slab layers are required. With the introduction of the Propagation Saw Test (PST) in the mid-2000s, various studies used particle tracking analysis of high-speed video recordings of PST experiments to gain insight into crack propagation processes, including slab bending, weak layer collapse, crack propagation speed and the frictional behavior after weak layer fracture. However, the resolution of the videos and the methodology used did not allow insight into dynamic processes such as the evolution of crack speed within a PST or the touchdown distance, which is the length from the crack tip to the trailing point where the slab sits on the crushed weak layer at rest again. Therefore, to study the dynamics of crack propagation we recorded PST experiments using a powerful portable high-speed camera with a horizontal resolution of 1280 pixels at rates up to 20,000 frames per second. By applying a high-density speckling pattern on the entire PST column, we then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer, and substrate. The high frame rates allowed time derivatives to obtain velocity and acceleration fields. On the one hand, we demonstrate the versatile capabilities and accuracy of the DIC method by showing three PST experiments resulting in slab fracture, crack arrest and full propagation. On the other hand, we present a methodology to determine relevant characteristics of crack propagation: the crack speed and touchdown distance within a PST, and the specific fracture energy of the weak layer. To estimate the effective elastic modulus of the slab and weak layer as well as the weak layer specific fracture energy we used a recently proposed mechanical model. A comparison to already established methods showed good agreement. Furthermore, our methodology also provides insight into the three different propagation results found with the PST and reveals intricate dynamics that are otherwise not accessible.

Mechanical Properties and Fracture Energy of Concrete Beams Reinforced with Basalt Fibres

2022 ◽  
Author(s):  
Ana Caroline Da Costa Santos ◽  
Paul Archbold
Keyword(s):  
Tensile Strength ◽  
Reinforced Concrete ◽  
Fracture Energy ◽  
Mechanical Performance ◽  
Plain Concrete ◽  
Natural Fibre ◽  
Bending Test ◽  
Natural Material ◽  
Fibre Reinforced Concrete ◽  
Steel Fibres

Fibre-reinforced concrete (FRC) is widely employed in the construction industry, with assorted fibre types being used for different applications. Typically, steel fibres give additional tensile strength to the mixture, while flexible fibres may be used in large sections, such as floor slabs, to control crack width and to improve the handling ability of precast sections. For many reasons, including durability concerns, environmental impact, thermal performance, etc, alternatives to the currently available fibres are being sought. This study examines the potential of using basalt fibres, a mineral and natural material, as reinforcement of concrete sections in comparison to steel fibres and plain concrete mix. Mixes were tested containing 0.5% and 1.0% of basalt fibres measuring 25mm length, 0.5% of the same material with 48mm length and steel fibres measuring 50mm by 0.05%, 0.1%, 0.15% and 0.2% of the concrete volume. For the mechanical performance analysis, the 3-point bending test was led and the fracture energy, Young’s modulus and tensile strength in different moments of the tests were calculated. When compared to the control mixtures and the steel-fibre-reinforced concrete, the mixes containing basalt had a reduction in their elastic modulus, representing a decrease in the concrete brittleness. At the same time, the fracture energy of the mixtures was significantly increased with the basalt fibres in both lengths. Finally, the flexural strength was also higher for the natural fibre reinforced concrete than for the plain concrete and comparable to the results obtained with the addition of steel fibres by 0.15%.

Identification of AAAS Composites Mechanical Fracture Parameters

2021 ◽  
Vol 322 ◽  
pp. 66-71
Author(s):  
Martin Lipowczan ◽  
David Lehký ◽  
Iva Rozsypalová ◽  
Petr Daněk ◽  
Pavla Rovnaníková ◽  
...  
Keyword(s):  
Fracture Energy ◽  
Modulus Of Elasticity ◽  
Crack Mouth Opening Displacement ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Specific Fracture Energy ◽  
Static Modulus ◽  
Fracture Parameters ◽  
Static Modulus Of Elasticity ◽  
Specific Fracture

The paper deals with selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors in terms of characterization by mechanical fracture parameters. Two composites made of brick dust as a precursor and an alkaline activator with a silicate modulus Ms = 1.0 were investigated. The composites differed in the fineness of grinding of the precursor – in the first set it was 0 to 1 mm, in the second set 0 to 0.3 mm. The filler was crushed brick. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were provided with notches in the middle of the span up to 1/3 of the depth of the specimens after 28 days of hardening. Five to six specimens from each composite set were tested. The specimens were subjected to three-point bending tests, in which force vs. displacement (deflection in the middle of the span) diagrams (F–d diagrams) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. After correction of these diagrams, the values of static modulus of elasticity, effective fracture toughness, effective toughness and specific fracture energy were determined using the Effective Crack Model and the Work-of-Fracture method. After the fracture experiments, the values of informative compressive strength were determined on one of the fractured parts. At the same time, the values of static modulus of elasticity, tensile strength and specific fracture energy were identified using artificial neural networks and F–d diagrams measured and simulated in the ATENA FEM software. All evaluations included the determination of basic statistics of parameters.

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