The outlook for regulatory support for adoption of efficient concretes

2021 ◽  
Vol 2124 (1) ◽  
pp. 012027
Author(s):  
A I Gabitov ◽  
A N Ryazanov ◽  
A S Salov ◽  
A R Biktasheva
Keyword(s):  
Bending Strength ◽  
Mouth Opening ◽  
Fiber Content ◽  
Fiber Reinforced Concrete ◽  
Crack Mouth Opening Displacement ◽  
Tunnel Construction ◽  
Displacement Curve ◽  
Crack Mouth ◽  
Fiber Concrete ◽  
Average Residual

Abstract The analysis of data obtained under studying scientific, technical and normative literature in the area of applying efficient concretes, in particular, fiber-reinforced concrete, in the world and national tunnel construction is presented herein. The European regulatory documents, standard metrologically certified methods and procedures for analyzing and testing, laboratory test equipment and measuring instruments are indicated. Steel fiber concrete studies was explored at the Scientific and Educational Center for Innovative Technologies of the Architectural and Construction Institute of the Ufa State Petroleum Technical University. Prism bending tests were made with different fiber content. In addition to laboratory tests, other tests were made in accordance with the Russian standards, where the prisms are tested without a notch. The correlation between the slope of the load-to-displacement curve of the crack mouth (CMOD - Crack Mouth Opening Displacement) and the length of the crack was used in the course of the study. The fiber content enabling to get an average residual bending strength of at least 1.5 MPa at 0.5 CMOD (equivalent to 0.47 mm center deviation) and an average residual bending strength of at least 1 MPa at 3.5 mm CMOD (equivalent to 3.02 mm of center deviation) is found. Statistical distributions of the Grubbs tests are analyzed by methods of statistical modeling. The regulatory framework for fiber concrete is not currently well developed in the Russian Federation, thereby reducing greatly the application of new generation concretes meeting the current knowledge. The application of fiber concrete in tunnel construction will prove to be economically justified and the areas of applying effective materials are to be developed in future with the wide participation of scientific, design, production, construction and other specialized organizations, as well as educational and training centers.

TEST STUDY ON THE BEST PASTING LAYER OF FRP REINFORCED CONCRETE

2019 ◽  
Vol 27 (02) ◽  
pp. 1950105
Author(s):  
XIANGQIAN FAN ◽  
JUEDING LIU
Keyword(s):  
Fracture Toughness ◽  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Crack Depth ◽  
Mouth Opening ◽  
Bending Test ◽  
Crack Mouth Opening Displacement ◽  
Displacement Curve ◽  
Crack Mouth ◽  
Opening Displacement

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.

Application of a Novel Crack Mouth Opening Displacement Partitioning Technique to Creep Crack Growth Tests on SEN(T) Geometries of Type 316H Stainless Steel

2020 ◽  
Author(s):  
Jorge de Andres ◽  
Michael D. Jones ◽  
Catrin M. Davies
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Uniaxial Tensile ◽  
Strain History ◽  
Uniaxial Tensile Test ◽  
Crack Mouth ◽  
Creep Crack ◽  
The Impact

Abstract A new technique has recently been proposed to provide improved estimates of the creep contribution to the crack mouth opening displacements (CMOD) and displacement rates during creep crack growth (CCG) tests. This technique employs finite element analysis that incorporates material specific uniaxial tensile test data to simulate crack growth in an experimental test and can account for strain history and creep stress relaxation effects during CCG tests. In this work, this new methodology is applied to analyse the results of a CCG test performed on a relatively low constraint single edge notched tension, SEN(T), geometry. The proportions of the CMOD due to elasticity and plasticity are quantified, and compared to historic, standardised methods of estimating these values. The new method reduces the over estimation of the contribution of plasticity to the CMOD measurement. The impact of this analysis on CCG test results is discussed.

Post-Cracking Steel Fiber Reinforced Concrete Slabs with Subsoil Interaction

2014 ◽  
Vol 1020 ◽  
pp. 210-214
Author(s):  
Daniel Pieszka ◽  
Karel Kubečka ◽  
Ivan Kološ
Keyword(s):  
Tensile Strength ◽  
Crack Opening ◽  
Mouth Opening ◽  
Fiber Reinforced Concrete ◽  
Flexural Behavior ◽  
Crack Mouth Opening Displacement ◽  
Steel Fiber Reinforced Concrete ◽  
Opening Displacement ◽  
Flexural Tensile Strength ◽  
Reinforced Concrete Slabs

The aim of the paper is to investigate the flexural behavior and property changes of concrete structures reinforced by steel fibers (SFRC) and to use the results for carrying capacity assessment of SFRC post-cracked slab on ground structure with subsoil interaction effect. Because the national codes cover neither design nor assessment of SFRC structures the investigation is generally based on the nonlinear fracture mechanics models to establish the stress-crack opening and load-crack mouth opening displacement relationship. Then the flexural tensile strength and residual flexural tensile strength of the post-cracked SFRC structure is determined with respect to subsoil interaction.

Crack Mouth Opening Displacement-Based η Factors for SE(B) Specimens

2009 ◽  
Vol 37 (4) ◽  
pp. 102116
Author(s):  
M. R. Mitchell ◽  
R. E. Link ◽  
J. P. Petti ◽  
R. H. Dodds, Jr. ◽  
R. E. Link
Keyword(s):  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Crack Mouth ◽  
Opening Displacement ◽  
Displacement Based

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

2014 ◽  
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.

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

2016 ◽  
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.

Research on Fracture-CMOD Toughness of Steel Fiber Reinforced Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 1784-1787
Author(s):  
Xiao Wei Wang ◽  
Wen Ling Tian ◽  
Ling Ling Fan ◽  
Ming Jie Zhou ◽  
Xiao Yan Zhao
Keyword(s):  
Fracture Toughness ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Estimation Error ◽  
Mouth Opening ◽  
Fiber Reinforced Concrete ◽  
Crack Mouth Opening Displacement ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Toughness Index

In order to study the fracture toughness of steel fiber reinforced concrete (SFRC) and the postcracking toughness evaluation method, the fracture toughness tests were done for the four types of steel fibers and three kinds of matrix strength. According to the experiment curves of the load and the crack mouth opening displacement (Load-CMOD), the fracture toughness of SFRC was studied; the formulas of the postcracking toughness coefficient and the Fracture-CMOD toughness index were established. The experiment results show that the Fracture-CMOD toughness index can reflect sensitively to the effect on concrete toughness of the type of the steel fiber, and then it is avoid that the estimation error of the initial cracking point led to the evaluation error of the toughness.Comparison with other fibers B fiber shows the best crack resistance and the toughening ability.

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