scholarly journals Effect of Stirrup on Bond Strength Degradation in Concrete Cracked by Expansion Agent Filled Pipes

2021 ◽  
Vol 11 (19) ◽  
pp. 8874
Author(s):  
Amadou Sakhir Syll ◽  
Hiroki Shimokobe ◽  
Toshiyuki Kanakubo
Keyword(s):  
Bond Strength ◽  
Crack Width ◽  
Strength Degradation ◽  
Structural Safety ◽  
Volumetric Expansion ◽  
Pull Out ◽  
Proposed Model ◽  
Coefficients Of Variation ◽  
Bond Degradation ◽  
The Impact

The corrosion of rebars in reinforced concrete structures cracks the concrete, which leads to the degradation of the bond strength between the rebar and concrete. Since bond deterioration can menace structural safety, bond strength evaluation is essential for proper maintenance. In this study, the authors investigated bond strength degradation by conducting pull-out tests on concrete specimens, with induced crack width and stirrups ratio being the principal parameters. An expansion agent-filled pipe (EAFP) simulates cracks due to the volumetric expansion of the corroded rebar. One advantage of this method is that it allows one to focus on the single effect of an induced crack. The pull-out tests on 36 specimens show that stirrups’ confinement significantly influences the bond degradation due to induced cracks. The authors proposed an empirical model for the degradation of bond strength, considering the impact of induced crack width. The result shows that the induced crack by EAFP can quantify the exclusive consequence of corrosion on bonds. Furthermore, the coefficient of variation is 12% for specimens without stirrup from Law et al. For specimen without and with stirrup from Lin et al., the coefficients of variation are 14% and 17%. The proposed model can predict the corroded specimen from the literature with reasonable accuracy.

Bond behaviour of chemically prestressed textile reinforced concrete

2019 ◽  
Author(s):  
Katarzyna Zdanowicz ◽  
Boso Schmidt ◽  
Hubert Naraniecki ◽  
Steffen Marx
Keyword(s):  
Reinforced Concrete ◽  
Bond Strength ◽  
Crack Width ◽  
Research Programme ◽  
Textile Reinforced Concrete ◽  
Self Compacting Concrete ◽  
Bond Behaviour ◽  
Bond Slip ◽  
Laser Sensors ◽  
Pull Out

<p>The bond behaviour of concrete specimens with carbon textile reinforcement was investigated in the presented research programme. Pull-out specimens were cast from self-compacting concrete with expansive admixtures and in this way chemical prestress was introduced. The aim of the research was to compare bond behaviour between prestressed specimens and non-prestressed control specimens. During pull-out tests, the pull-out force and notch opening were measured with a load cell and laser sensors. Further, bond - slip and pull-out force - crack width relationships were drawn and compared for prestressed and non-prestressed specimens. Chemically prestressed specimens reached 24% higher bond strength than non-prestressed ones. It can be therefore concluded, that chemical prestressing positively influences the bond behaviour of concrete with textile reinforcement and thus better utilisation of its properties can be provided.</p>

Effects of Fatigue Damage on Bond Behavior between Corroded Rebar and Concrete

2019 ◽  
Author(s):  
Yunpeng Zhang ◽  
Weiping Zhang ◽  
You Hu
Keyword(s):  
Bond Strength ◽  
Fatigue Damage ◽  
Current Method ◽  
Fatigue Loading ◽  
Repeated Loading ◽  
Relative Slip ◽  
Pull Out ◽  
Bond Degradation ◽  
Impressed Current ◽  
Different Levels

Bond degradation due to rebar corrosion and fatigue loading may affect the serviceability and even safety of reinforced concrete (RC) bridges. 15 specimens confined with stirrups were cast for eccentric pull-out tests, and 12 of them were corroded with the target mass loss of 0.03 by the impressed current method. Monotonic pull-out tests were conducted on three corroded and three uncorroded specimens. Wavy descending branch was found in bond stress-slip test curves of uncorroded specimens attributed to stirrup confinement, however it disappeared in those curves of the corroded specimens due to the corrosion loss of rebar transverse ribs. Based on the tested monotonic bond strength, the other nine corroded specimens of different fatigue damages were obtained through repeated loading with different levels and cycles before undergoing monotonic pull-out tests. It is observed that the relative slip increases with a gradually decreasing rate as the loading cycles increase. The monotonic tests of specimens with fatigue damage show that the bond strength increases to a certain value and then decreases with the increase of fatigue loading cycles. Moreover, the higher the loading level is, the fewer cycles are needed to reach the maximum bond strength. In addition, the peak slip corresponding to bond strength decreases with the increase of fatigue loading cycles.

scholarly journals The influence of total reinforcement anchorage length on misinterpretation of the impact of hot-dip galvanised steel corrosion on its bond strength with concrete

2016 ◽  
Vol 60 (1) ◽  
pp. 13-20 ◽  
Author(s):  
P. Pokorný ◽  
J. Čech ◽  
P. Tej ◽  
M. Vokáč
Keyword(s):  
Bond Strength ◽  
Negative Impact ◽  
Steel Corrosion ◽  
Anchorage Length ◽  
Pull Out ◽  
Galvanised Steel ◽  
Strength Tests ◽  
Short Test ◽  
The Impact ◽  
Total Reinforcement

Abstract To begin with, the intorduction of this paper summarises literature sources that wrongly interpret results of the bond strength between hot-dip galvanised reinforcements and concrete. The influence of the total reinforcement anchorage length on the bond strength results assessment was studied in detail. The numeric analysis of beam models with various testing anchorage lengths (the analysis input data comprised the results of previous bond strength tests carried out in a laboratory) unambiguously confirmed that when the bond strength between concrete and hot-dip galvanised reinforcement with a sufficient test anchorage length is tested in a beam test, the negative impact of the coating corrosion on bond strength with concrete may be biased. It is more objective to test bond strength with concrete in a pull-out test where a very short test reinforcement anchorage length is set out as a standard.

scholarly journals Regression Analysis of Bond Parameters between Corroded Rebar and Concrete Based on Reported Test Data

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
H. J. Zhou ◽  
Y. F. Zhou ◽  
Y. N. Xu ◽  
Z. Y. Lin ◽  
F. Xing ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Bond Strength ◽  
Crack Width ◽  
Experimental Tests ◽  
Test Results ◽  
Bond Slip ◽  
Regression Effect ◽  
Pull Out ◽  
Maximum Crack ◽  
Best Fit

Reinforcement corrosion is a major cause of degradation in reinforced concrete structures. The fragile rust layer and cracking and spalling of the cover caused by splitting stress due to rust expansion can alter bond behaviors significantly. Despite extensive experimental tests, no stochastic model has yet incorporated randomness into the bond parameters model. This paper gathered published experimental data on the bond-slip parameters of pull-out specimens and beam-end specimens. Regression analysis was carried out to identify the best fit of bond strength and the corresponding slip value in the context of different corrosion levels from the recollected test results. An F-test confirmed the regression effect to be significant. Residual data were also analyzed and found to be well described by a normal distribution. Crack width data of the tested specimens were also collected. A regression analysis of the bond strength and maximum crack width was carried out given the comparative simplicity of measuring crack width versus rebar area loss. Results indicate that maximum crack width can also be used to predict bond strength degradation with similar variation magnitude.

scholarly journals Numerical Study of the Bond Strength Evolution of Corroded Reinforcement in Concrete in Pull-Out Tests

2022 ◽  
Vol 12 (2) ◽  
pp. 654
Author(s):  
Eliass El Alami ◽  
Fatima-Ezzahra Fekak ◽  
Luigi Garibaldi ◽  
Hassane Moustabchir ◽  
Ahmed Elkhalfi ◽  
...  
Keyword(s):  
Bond Strength ◽  
Numerical Study ◽  
Damage Model ◽  
Concrete Cover ◽  
Embedment Depth ◽  
Pull Out ◽  
Strength Evolution ◽  
Concrete Damage ◽  
The Impact ◽  
2D Numerical Model

The corrosion of rebars in reinforced concrete structures impacts their geometry (diameter and ribs) and mass, damages the concrete at the interface between the two materials, deteriorates the bond strength, and causes the cracking of the concrete cover. In the following study, a 2D numerical model of the pull-out test is presented in order to study the impact of corrosion on the bond strength. Several parameters are investigated: the embedment depth, the rebar’s diameter, and the width of the concrete cover. The model reproduces the slip of the rebar and the failure through the splitting of concrete. It integrates an interface between the two materials and a concrete damage model that simulate the deterioration of concrete in compression and tension. The results obtained are validated with experimental data from the literature. Moreover, a parametric study is carried out to determine the impact of the embedment depth, the diameter of the rebar, and the concrete cover on the bond strength. The present study confirms that a greater embedment depth increases the pulling load. The study also confirms that the rebar’s diameter impacts highly the loss of bond between the rebar and the concrete cover. Lastly, the final main result of this paper is that the width of the concrete cover slows the loss of bond strength between the two materials.

scholarly journals Photodynamic Therapy (PDT) in Prosthodontics: Disinfection of Human Teeth Exposed to Streptococcus mutans and the Effect on the Adhesion of Full Ceramic Veneers, Crowns, and Inlays: An In Vitro Study

Biomedicines ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 144
Author(s):  
Corina Elena Tisler ◽  
Radu Chifor ◽  
Mindra Eugenia Badea ◽  
Marioara Moldovan ◽  
Doina Prodan ◽  
...  
Keyword(s):  
Bond Strength ◽  
Streptococcus Mutans ◽  
In Vitro Study ◽  
Human Teeth ◽  
Pull Out ◽  
Tooth Surfaces ◽  
Adhesive Cementation ◽  
Ceramic Restorations ◽  
The Impact

The use of PDT in prosthodontics as a disinfection protocol can eradicate bacteria from tooth surfaces by causing the death of the microorganisms to which the photosensitizer binds, absorbing the energy of laser light during irradiation. The aim of the study was to investigate the capacity of PDT to increase the bond strength of full ceramic restorations. In this study, 45 extracted human teeth were prepared for veneers, crowns, and inlays and contaminated with Streptococcus mutans. Tooth surfaces decontamination was performed using a diode laser and methylene blue as a photosensitizer. The disinfection effect and the impact on tensile bond strength were evaluated by scanning electron microscopy (SEM) and pull-out tests of the cemented ceramic prosthesis. Results show that the number of bacteria was reduced from colonized prepared tooth surfaces, and the bond strength was increased when PDT was used. In conclusion, the present study indicates that using PDT as a protocol before the final adhesive cementation of ceramic restorations could be a promising approach, with outstanding advantages over conventional methods.

Local bond strength prediction of deformed reinforcing bars in concrete considering heterogeneity at interface regions

2021 ◽  
pp. 1-20
Author(s):  
Shutong Yang ◽  
Miao Yu ◽  
Kun Dong ◽  
Yushan Yang
Keyword(s):  
Bond Strength ◽  
Boundary Effect ◽  
Characteristic Parameter ◽  
Cementitious Materials ◽  
Reinforcing Bars ◽  
Pull Out ◽  
Proposed Model ◽  
Fibre Reinforced Polymer ◽  
Interfacial Characteristic ◽  
Average Bond

An analytical model is proposed to predict local bond strength (τf) by incorporating heterogeneity at interface regions for deformed reinforcing bars centrally anchored in concrete. The rib width on the bar surface is introduced as an interfacial characteristic parameter G in the proposed model; this accounts for the heterogeneity. Both τf and the local interfacial fracture energy (GIIf) of each specimen were found to be linked to G and can be determined analytically from the maximum pull-out loads (Fmax) from tests. It was found that the predicted τf was larger than the maximum average bond stress (τavg-max); the discrepancy between the two values reduced with an increase in L/G. Moreover, with an increase in L/G, the predicted τf showed a certain decrease, with the reduction decreasing with stronger interfacial homogeneity. The predicted GIIf was found to be significantly increased because of the weaker boundary effect. The validity of the proposed model was verified using comparisons of predicted Fmax (using the determined values of τf and GIIf) and the experimental Fmax, with the only failure mode being bar pull-out. Moreover, the model can be applied to steel or fibre-reinforced polymer bars and the concrete refers to all types of cementitious materials.

Test of Mediation and Moderation between Employee Empathy and Customers’ Advocacy

2020 ◽  
Author(s):  
Sajjad Ahmad Afridi ◽  
Asad Shahjehan ◽  
Maqsood Haider ◽  
Dr Uzma Munawar
Keyword(s):  
Factor Analysis ◽  
Customer Loyalty ◽  
Service Sector ◽  
Mediating Effect ◽  
First Line ◽  
Private Hospitals ◽  
Proposed Model ◽  
Confirmatory Factor ◽  
The Impact ◽  
Significant Moderator

This study examined the impact of employee empathy on customers’ advocacy directly and indirectly through customers’ loyalty. Moreover, the interacting effect of customers’ trust was verified between the association of customers’ loyalty and advocacy. The attributes of the proposed model were examined in the context of first line employee and patients’ interactions. A total of 220 responses were collected for analysis from the private hospitals of Peshawar. The model fitness was confirmed through confirmatory factor analysis and hypotheses were examined. Findings confirmed the positive and significant impact of employee empathy on customers’ advocacy. Further, the mediating effect was examined and found that loyalty partially mediates employee empathy and customers’ advocacy. Additionally, trust was found a significant moderator between the association of customer loyalty and advocacy. Furthermore, findings revealed that trust based loyalty significantly and positively mediates employee empathy and customers’ advocacy. Findings of the present study provide understanding for the service sector, particularly in healthcare, to enhance customers’ loyalty, advocacy, and trust through service employee’s empathic aptitude. Keywords: Employee empathy, Service Eco-system, Customers’ Loyalty, Customers’ Advocacy, Trust-Based Loyalty, Healthcare, S-D Logic

The impact of duration observations on precision of results GNSS measurements

2017 ◽  
Vol 921 (3) ◽  
pp. 7-13 ◽  
Author(s):  
S.V. Grishko
Keyword(s):  
Measurement Accuracy ◽  
Functional Dependence ◽  
Observation Time ◽  
Satellite Networks ◽  
Satellite Measurements ◽  
Proposed Model ◽  
Actual Error ◽  
Gnss Measurements ◽  
The Impact ◽  
Qualitative Characteristics

This paper shows that the accuracy of relative satellite measurements depend not only on the length of the baseline, as it is regulated by the rating formula of accuracy of GNSS equipment, but also on the duration of observations. As a result of the strict adjustment much redundant satellite networks with different duration of observations obtained covariance matrix of baselines, the most realistic reflecting the actual error of satellite observations. Research of forms of communication of these errors from length of the baseline and duration of its measurement is executed. A significant influence of solar activity on accuracy of satellite measurements, in general, leads to unequal similar series of measurements made at different periods, for example, in the production of monitoring activities. The model of approximation of the functional dependence of accuracy of the baseline from its length and duration of observations having good qualitative characteristics is offered. Based on the proposed model, we analyzed the dynamics of changes in measurement accuracy with an increase in observation time.

Sign in / Sign up

Export Citation Format

Share Document