scholarly journals On Bond-slip of EB-FRP/Concrete Interface in Shear Under Fatigue Loading: Review and Synthesis of Experimental Studies and Models

2022 ◽  
Vol 11 (1) ◽  
pp. 1-19
Author(s):  
Abbas Fathi ◽  
Georges El-Saikaly ◽  
Omar Chaallal
Keyword(s):  
Structural Damage ◽  
Fatigue Behavior ◽  
Experimental Studies ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
Design Guidelines ◽  
Rc Structures ◽  
Bond Slip ◽  
Wide Range ◽  
Concrete Interface

Reinforced concrete (RC) structures subjected to cyclic fatigue loading are prone to progressive damage. Among the types of structural damage, those leading to shear deficiencies can result in sudden rupture of structures without warning. Hence, RC structures deficient in shear urgently need retrofitting. The use of externally bonded (EB) fiber-reinforced polymer (FRP) composites presents many advantages and is a very promising technology for shear strengthening of RC structures. This paper encompasses a wide range of research findings related to the interaction between concrete and FRP under fatigue loading. The behavior of the bond between FRP and concrete plays a major role in the failure mode of FRP shear-strengthened structures especially under fatigue. Therefore, it is of interest to characterize the FRP/concrete interaction using appropriate models with respect to the influencing parameters. The paper will first discuss existing design guidelines and considerations related to the fatigue behavior of RC structures. A thorough review of available literature on EB-FRP/concrete bond in shear under cyclic fatigue loading will then be presented, with a focus on proposed bond-slip models and finite element studies of the FRP/concrete interface under fatigue loading.

On the in vitro Fatigue Behavior of Human Dentin: Effect of Mean Stress

2004 ◽  
Vol 83 (3) ◽  
pp. 211-215 ◽  
Author(s):  
R.K. Nalla ◽  
J.H. Kinney ◽  
S.J. Marshall ◽  
R.O. Ritchie
Keyword(s):  
Fatigue Failure ◽  
Fatigue Behavior ◽  
Load Ratio ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
R Ratio ◽  
Wide Range ◽  
Human Dentin ◽  
Mean Stresses

Human dentin is susceptible to failure under repetitive cyclic-fatigue loading. This investigation seeks to address the paucity of data that reliably quantify this phenomenon. Specifically, the effect of alternating vs. mean stresses, characterized by the stress- or load-ratio R (ratio of minimum-to-maximum stress), was investigated for three R values (−1, 0.1, and 0.5). Dentin was observed to be prone to fatigue failure under cyclic stresses, with susceptibility varying, depending upon the stress level. The “stress-life” ( S/N) data obtained are discussed in the context of constant-life diagrams for fatigue failure. The results provide the first fatigue data for human dentin under tension-compression loading and serve to map out safe and unsafe regimes for failure over a wide range of in vitro fatigue lives (< 103 to > 106 cycles).

Damage Assessment of Similar Martensitic Welds Under Creep, Fatigue and Creep-Fatigue Loading

2020 ◽  
Author(s):  
Thorben Bender ◽  
Andreas Klenk ◽  
Stefan Weihe
Keyword(s):  
Base Metal ◽  
Fatigue Behavior ◽  
Base Material ◽  
Fatigue Loading ◽  
Design Guidelines ◽  
Failure Behavior ◽  
Martensitic Steels ◽  
Viscoplastic Material ◽  
Local Strains ◽  
Creep Fatigue

Abstract For the assessment of welds under high-temperature conditions in the creep or creep-fatigue regimes, the knowledge on the damage location and its temporal evolution are of high importance. The failure behavior of similar welds of ferritic-martensitic steels in the creep regime is well known. For creep-fatigue loading, the behavior of welds is still subject to research but it seems that the heat affected zone (HAZ) limits the lifetime of welded components as well. This local failure behavior is not reflected in design guidelines using weld reduction factors or in typical assessment approaches. The evaluation of local strains and stresses in the HAZ is unavoidable. For the improvement of design and inspection guidelines, a more detailed consideration of weld behavior is of interest. In this paper, an overview of current developments in the assessment of welds under creep, fatigue, and creep-fatigue loading conditions is given. An assessment approach for creep damage and failure, including the prediction of rupture time and location, is presented. The assessment is based on numerical analyses considering the different behavior of base material and HAZ represented by three different subzones. The approach is validated with the simulation of a uniaxial cross weld, creep crack, and component tests. Whereas the creep behavior of the HAZ compared to base metal is quite well known, there is only little knowledge of their fatigue behavior. Using a set of fatigue tests on HAZ, base metal specimens and cross weld specimens, the influence of fatigue and creep-fatigue loading on the lifetime and failure location of a weld will be discussed. For the numerical simulations, a viscoplastic material law of Chaboche type is used and an evaluation of the local strains in the HAZ allows an attempt to explain the observed failure locations.

FE Modeling of FRP-Concrete Interface for very High Cycle Fatigue Behavior

2013 ◽  
Vol 577-578 ◽  
pp. 165-168 ◽  
Author(s):  
M. Mahal ◽  
T. Blanksvärd ◽  
B. Täljsten
Keyword(s):  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Finite Element Program ◽  
Element Program ◽  
Three Dimensional Finite Element ◽  
Concrete Interface

The fatigue damage of FRP-concrete interface is a major problem in strengthened structures subjected to fatigue loading. The available FRP-concrete interface models published in the literature usually deal with fracture mechanism approach, which is unsuitable for high cycle fatigue damage. In this study, a constitutive micro model is developed for FRP-concrete interface for high cycle fatigue and incorporated into a three dimensional finite-element program. Numerical analysis of a double lap joint is carried out, and the results show that the proposed model is reasonably accurate.

scholarly journals Innovative experimental and finite element assessments of the performance of CFRP-retrofitted RC beams under fatigue loading

2018 ◽  
Vol 25 (4) ◽  
pp. 661-678
Author(s):  
Ata Hojatkashani ◽  
Mohammad Zaman Kabir
Keyword(s):  
Finite Element ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Experimental Studies ◽  
Fatigue Loading ◽  
Element Model ◽  
Fiber Reinforced Polymers ◽  
Rc Beams ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Polymers

Abstract Numerous experimental studies have proven the efficiency of externally bonded fiber-reinforced polymer (FRP) systems on structural concrete elements, such as reinforced concrete (RC) beams. The current paper presents an analytical formulation of mechanical constants based on the results of experimental data, which were acquired from fatigue testing of intact and CFRP-retrofitted RC beams. A total of six scaled RC beams were prepared for the test, three of which were strengthened with carbon fiber-reinforced polymers (CFRPs). A specific finite element model coupled with experimental results from the proposed RC beams made it possible to compare the theoretical and experimental fatigue behavior of RC beams with and without composite reinforcement. The developed numerical model was then extended to evaluate a higher number of fatigue load cycles, as recommended by bridge codes. This was carried out to monitor the performance of CFRP-retrofitted RC beams in terms of flexural stiffness deterioration and damage propagation. The relationships presented in this paper were calibrated to the tested specimens. Moreover, they were useful for the design of RC and CFRP-retrofitted RC beams and for predicting fatigue performance, including the damage behavior of constituent materials.

Characterization of Piezo Fiber-Based Sensors Responses in Multifunctional Composites

2011 ◽  
Vol 409 ◽  
pp. 633-638
Author(s):  
Mohammad Mehdizadeh ◽  
Sabu John ◽  
Chun H. Wang ◽  
Viktor Verijenko ◽  
Paul Callus
Keyword(s):  
Structural Damage ◽  
Structural Changes ◽  
Fibre Composite ◽  
Fatigue Loading ◽  
Civil Infrastructure ◽  
Sensor Failure ◽  
Multifunctional Composites ◽  
Wide Range ◽  
Health Monitoring Systems

Structural health monitoring systems (SHMS) are increasingly being considered for implementation in a wide range of industries, including transport, civil infrastructure, and energy production. As the application of SHM systems increase, it will be increasingly important to quantify the durability, reliability, and reparability of the SHM system. This paper investigates the electrical and electro-mechanical characteristics of piezoelectric sensors in an attempt to distinguish sensor failure from structural damage [10]. This study involved the measurements of pertinent electrical properties for MFC (Macro Fibre Composite) sensor under fatigue loading and comparison of the strain measurements to characterize the degradation of the structure as well as the MFC. Changes in the capacitance and inductance of this sensor have been recorded, highlighting deleterious structural changes in the sensor itself without any discernible change in the structure being monitored.

Numerical Evaluation of Splitting Performance of Prestressed Concrete Prisms With Larger Diameter Prestressing Wires

2019 ◽  
Author(s):  
Moochul Shin ◽  
Hailing Yu
Keyword(s):  
Prestressed Concrete ◽  
Structural Damage ◽  
Numerical Study ◽  
Experimental Studies ◽  
Concrete Cover ◽  
Small Scale ◽  
Slip Model ◽  
Cohesive Elements ◽  
Bond Slip ◽  
Pull Out

This numerical study focuses on evaluating the structural performance of prestressed concrete prisms with larger diameter (0.315 in) prestressing wires. More commonly used prestressing wires are the 0.209 in (5.32 mm) diameter wires for prestressed concrete crossties. However, there has been an interest to adopt larger diameter prestressing wires in order to provide higher prestress forces with the aim of mitigating the structural damage of prestressed concrete crossties. Previous experimental studies demonstrated that small-scale pretensioned concrete prisms had excellent correlation in bonding performance of concrete ties pretensioned with 0.209 in (5.32 mm) wires or three- or seven-wire strands. Using a finite element (FE) modeling approach, this study investigates the effects of 8 mm diameter prestressing wires on the splitting/bursting performance of prisms at the onset of de-tensioning of the wires. The studied parameters include geometrical/mechanical parameters such as thickness of the concrete cover, spacing between the wires, level of prestress forces, and concrete release strength in compression. Cohesive elements with a newly developed nonlinear bond-slip model are assigned to the interface between the prestressing wires and the surrounding concrete. The parameters for the bond-slip model are calibrated based on a simple pull-out test on concrete cylinders with the 0.315 in (8 mm) diameter wires. The simulation results are compared with the predicted splitting performance of prisms pretensioned with 0.209 in (5.32 mm) wires or seven-wire strands. Based on the FE analysis results, recommendations are made on the minimum concrete cover thickness and wire spacing required to achieve acceptable splitting/bursting performance in prestressed concrete prisms.

Differentiating Structural Damage From Piezo-Fibre-Based Sensor Damage in Multifunctional Composites

2011 ◽  
Author(s):  
Mohammad Mehdizadeh ◽  
Sabu John ◽  
Chun H. Wang ◽  
Viktor Verijenko ◽  
Wayne Rowe ◽  
...  
Keyword(s):  
Structural Damage ◽  
Energy Production ◽  
Structural Changes ◽  
Fatigue Loading ◽  
Piezoelectric Sensors ◽  
Civil Infrastructure ◽  
Sensor Failure ◽  
Multifunctional Composites ◽  
Wide Range ◽  
Health Monitoring Systems

Structural health monitoring systems (SHMS) are increasingly being considered for implementation in a wide range of industries, including transport, civil infrastructure, and energy production. As the application of SHM systems increase, it will be increasingly important to quantify the durability, reliability, and reparability of the SHM system. This paper investigates the electrical and electro-mechanical characteristics of piezoelectric sensors in an attempt to distinguish sensor failure from structural damage. This study involved the measurements of pertinent electrical properties for three various types of advanced piezoelectric sensors under fatigue loading. Changes in the capacitance and inductance of these sensors have been recorded, highlighting the deleterious structural changes in the sensor itself without any discernible change in the structure being monitored.

Mechanical Behaviour of ZrO2-Bioglass Dental Ceramics under Cyclic Fatigue Loading

2010 ◽  
Vol 636-637 ◽  
pp. 47-53 ◽  
Author(s):  
Luiz A. Bicalho ◽  
Claudinei dos Santos ◽  
R.C. Souza ◽  
M.R.J. Barboza ◽  
Carlos Antonio Reis Pereira Baptista
Keyword(s):  
Fatigue Life ◽  
Bending Strength ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
Sem Analysis ◽  
Modulus Of Rupture ◽  
Dental Ceramics ◽  
Four Point Bending ◽  
Number Of Cycles

The cyclic fatigue life of 3mol%Y2O3-stabilized ZrO2 (3Y-TZP) ceramics doped with bioactive glass has been investigated. Samples of 3Y-TZP containing 3 or 5wt% of bioglass were sintered at 1300oC for 120 minutes. Sintered samples were characterized by relative density, XRD and SEM analysis. Mechanical properties of hardness and fracture toughness were determined using Vickers indentation method and Modulus of Rupture was determined by four-point bending testing. Furthermore, the reliability of the samples was estimated using Weibull statistic analysis. The cyclic fatigue life was estimated using four-point bending testing under frequency of 25Hz and stress ratio, R, of 0.1. Highly dense tetragonal ZrO2 samples were obtained after sintering and presented hardness of 10.5 and 11GPa, KIC of 6 and 7MPam1/2, bending strength of 320 and 450MPa and Weibull’ modulus of 6 and 7 for samples containing 5 or 3% of bioglass respectively. The fatigue behavior indicates that the increasing of stress level leads to decreasing of the number of cycles and the number of run-out specimens. Fatigue behavior was similar for the two compositions tested. Samples containing 3% of bioglass are more resistant (near 10%) to fatigue presenting cyclic fatigue life near to 250MPa while samples with 5% presented fatigue limit near to 220MPa.

scholarly journals Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 421
Author(s):  
Dariusz Puchala ◽  
Kamil Stokfiszewski ◽  
Mykhaylo Yatsymirskyy
Keyword(s):  
Statistical Analysis ◽  
Image Encryption ◽  
Experimental Studies ◽  
Quality Measures ◽  
Input Image ◽  
Jpeg Compression ◽  
Image Statistics ◽  
Compression Stage ◽  
Wide Range ◽  
The Impact

In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.

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