Estimation of the Rebar Force in RC Members from the Analysis of the Crack Mouth Opening Displacement Based on Fracture Mechanics

To optimize the strengthening method using the fiber reinforced polymer (FRP) for the reinforcement of the concrete structure with cracks, the three-point bending test was conducted on the concrete beams wrapped with different layers of FRP materials. The strain gauges were pasted on the surface of the specimens to measure the initial cracking load. The crack mouth opening displacement (CMOD) was utilized to test the load–crack mouth opening displacement curve. According to the improved calculation formula of the fracture toughness, the critical effect crack length [Formula: see text], initiation fracture toughness [Formula: see text] and instability fracture toughness [Formula: see text] of specimens were calculated. The test results showed that, under the same initial crack depth, the peak load of FRP reinforced concrete decreases with the increase of FRP pasting layer. When there was one layer wrapped over the specimen, the instability toughness of the specimen reached the maximum value and the crack resistance was the best. Based on acoustic emission testing method, the acoustic emission parameters of the above-mentioned concrete during fracture process were identified and collected. The optimal layer of the FRP reinforced concrete with cracks was analyzed from the acoustic emission method.

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Revised η-Factors for 3P SE(B) Fracture Specimens Incorporating 3-D Effects

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2014-28135 ◽

2014 ◽

Cited By ~ 1

Author(s):

Rodolfo F. de Souza ◽

Claudio Ruggieri

Keyword(s):

Fracture Toughness ◽

Mouth Opening ◽

Estimation Procedure ◽

Crack Mouth Opening Displacement ◽

Evaluation Procedure ◽

Specimen Thickness ◽

Crack Mouth ◽

Opening Displacement ◽

Wide Range ◽

Fracture Specimens

Standardized procedures to measure cleavage fracture toughness of ferritic steels in the DBT region most commonly employ three-point bend fracture specimens, conventionally termed SE(B) or SENB specimens. The evaluation protocol of fracture toughness for these crack configurations builds upon laboratory records of load and crack mouth opening displacement (CMOD) to relate plastic work with J (or, equivalently, CTOD). The experimental approach employs a plastic η-factor to relate the macroscale crack driving force to the area under the load versus crack mouth opening displacement for cracked configurations. This work provides revised η-factors derived from CMOD records applicable to estimate the J-integral and CTOD in SE(B) specimens with varying crack size and specimen configuration. Non-linear finite element analyses for plane-strain and 3-D models provide the evolution of load with increased CMOD which is required for the estimation procedure. The analysis matrix considers SE(B) specimens with W = 2B and W = B configurations with and without side grooves covering a wide range of specimen thickness, including precracked Charpy (PCVN) specimens. Overall, the present results provide further validation of the J and CTOD evaluation procedure currently adopted by ASTM 1820 while, at the same time, giving improved estimation equations for J incorporating 3-D effects which enter directly into more accurate testing protocols for experimental measurements of fracture toughness values using 3P SE(B) specimens.

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Vibrated Concrete vs. Self-Compacting Concrete: Comparison of Fracture Mechanics Properties

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.601.199 ◽

2014 ◽

Vol 601 ◽

pp. 199-202

Author(s):

Sara Korte ◽

Veerle Boel ◽

Wouter de Corte ◽

Geert de Schutter

Keyword(s):

Fracture Mechanics ◽

Mouth Opening ◽

Bending Test ◽

Crack Mouth Opening Displacement ◽

Self Compacting Concrete ◽

Opening Displacement ◽

Three Point Bending ◽

Fracture Parameters ◽

Wedge Splitting Test ◽

Splitting Test

This study focuses on the fracture mechanics aspect of self-compacting concrete, compared to vibrated concrete. The most commonly used experiments to investigate the toughness and cracking behaviour of concrete are the three-point bending test (3PBT) on small, notched beams, and the wedge-splitting test (WST) on cubic samples with guiding groove and starter notch. From the resulting P-CMOD curves (applied load versus crack mouth opening displacement), different fracture parameters, such as fracture energy and fracture toughness, can be extracted. Moreover, using inverse analysis, the σ-w relationship (tensile stress versus crack width) can be derived. This paper lists the results of a series of tests on samples, made of VC, SCC of equal strength, and SCC with identical w/c factor. Subsequently, a comparison of the mechanical characteristics is made, revealing important differences regarding several fracture parameters.

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Deflection–crack mouth opening displacement relationship for concrete beams with and without fibres

Magazine of Concrete Research ◽

10.1680/macr.14.00310 ◽

2015 ◽

Vol 67 (10) ◽

pp. 532-540 ◽

Cited By ~ 4

Author(s):

Sujing Zhao ◽

Wei Sun ◽

David Lange

Keyword(s):

Concrete Beams ◽

Mouth Opening ◽

Crack Mouth Opening Displacement ◽

Crack Mouth ◽

Opening Displacement

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Determination of Parameters for the Damage Mechanics Approach to Ductile Fracture Based on a Single Fracture Mechanics Test

Volume 4: Materials Technology ◽

10.1115/omae2017-61425 ◽

2017 ◽

Author(s):

O. J. Coppejans ◽

C. L. Walters

Keyword(s):

Fracture Mechanics ◽

Damage Mechanics ◽

Mouth Opening ◽

Crack Mouth Opening Displacement ◽

Single Fracture ◽

Post Processing ◽

Local Approach ◽

Opening Displacement ◽

Failure Locus ◽

Material Points

The local approach to modelling ductile tearing is a useful technique to give insight into fracture mechanics. However, applications of the local approach have been stymied by the high cost of finding the parameters that characterize it because of the number of specimens and expensive post-processing that the testing requires. In this paper, a novel iterative method to extract a failure locus from one Crack Tip Opening Displacement (CTOD) specimen is presented. Material points fail under various different stress states in a CTOD specimen, so many different points on the failure locus can be found through thoughtful post-processing in FEA. A phenomological ductile failure locus is fitted through the stress triaxiality, Lode angle, and plastic strains that cause failure at material points in the CTOD test. Simulating a CTOD test with a different aspect ratio has shown that the failure locus found by this method can be predictive, giving both accurate force versus Crack Mouth Opening Displacement (CMOD) curves and realistic fracture surfaces featuring separate tunnelling and shear lips.

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Comparison of J-Integral Measurement Methods on Clamped Single-Edge Notched Tension Specimens

Volume 3: Operations, Monitoring and Maintenance; Materials and Joining ◽

10.1115/ipc2016-64610 ◽

2016 ◽

Cited By ~ 1

Author(s):

Timothy S. Weeks ◽

Jeffrey W. Sowards ◽

Ross A. Rentz ◽

David T. Read ◽

Enrico Lucon

Keyword(s):

Mouth Opening ◽

Surface Strain ◽

Image Correlation ◽

Crack Mouth Opening Displacement ◽

J Integral ◽

Crack Mouth ◽

Single Edge ◽

Opening Displacement ◽

Strain Gradients

This paper reports an extension of a previous study that compared methods of evaluating J by the crack mouth opening displacement and by surface strain gradients. Here, the surface strain gradients are measured by three-dimensional digital image correlation. The results herein represent a small test matrix that involved evaluation of the J-integral for clamped single-edge notched tensile specimens from API 5L X65 base-metal, weld metal and the adjacent heat affected zone; the J-integral was evaluated by a standardized procedure utilizing the crack mouth opening displacement (CMOD) and by the contour integral method on an external surface strain contour. Digital image correlation provides sufficient full-field strain data for use by this method and is considerably more robust than surface-mounted strain gage instrumentation. A series of validity checks are presented that demonstrate that the data are useful and valuable. Experimental determination of the J-integral is not limited to thoroughly analyzed test geometries and may be achieved with limited instrumentation. Furthermore, the method described does not require a determination of crack size nor any instrumentation that requires access to the crack mouth.

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Impact fracture behaviors of three-dimensional braided composite U-notch beam subjected to three-point bending

International Journal of Damage Mechanics ◽

10.1177/1056789518772619 ◽

2018 ◽

Vol 28 (3) ◽

pp. 404-426 ◽

Cited By ~ 10

Author(s):

Baohui Shi ◽

Shengkai Liu ◽

Amna Siddique ◽

Yongcan Du ◽

Baozhong Sun ◽

...

Keyword(s):

Three Dimensional ◽

Mouth Opening ◽

Impact Fracture ◽

Image Correlation ◽

Crack Mouth Opening Displacement ◽

Crack Mouth ◽

Opening Displacement ◽

Braided Composite ◽

Fracture Behaviors ◽

The Impact

Impact fracture behaviors of three-dimensional braided composites are critical to designing the braided composite parts. Here we report the impact fracture behaviors of three-dimensional braided composite U-notch beam tested on a modified split Hopkinson pressure bar. Crack mouth opening displacement, deformation process, and crack evolutions were recorded with high-speed photography camera. The digital image correlation method was used to calculate deformation contours of the braided composite. A microstructure model of the three-dimensional braided composite U-notch beam was established for analyzing damage evolution and fracture mechanisms. The histories of deformation, the load, and the crack mouth opening displacement were obtained from the impact fracture test and finite element analysis. It was found that the impact fracture resistance and morphologies were influenced by the braided structure and braided yarn orientations. The crack generated at the notch tip and then propagated along the braided angle direction rather than the perpendicular direction that often occurred for isotropic materials, such as the epoxy resin solid. The combinations of different braided angle and yarns are recommended for high impact fracture behavior design.

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