scholarly journals Nondestructive Evaluation of FRP-Concrete Interface Bond due to Surface Defects

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Nur Yazdani ◽  
Eyosias Beneberu ◽  
Mina Riad
Keyword(s):  
Nondestructive Evaluation ◽  
Surface Defects ◽  
Sample Surface ◽  
Small Scale ◽  
Bond Quality ◽  
Related Factors ◽  
Cfrp Laminates ◽  
Surface Wetness ◽  
Externally Bonded ◽  
Ground Penetrating

Carbon fiber-reinforced polymer (CFRP) laminates have been successfully used as externally bonded reinforcements for retrofitting, strengthening, and confinement of concrete structures. The adequacy of the CFRP-concrete bonding largely depends on the bond quality and integrity. The bond quality may be compromised during the CFRP installation process due to various factors. In this study, the effect of four such construction-related factors was assessed through nondestructive evaluation (NDE) methods, and quantification of the levels of CFRP debonding was achieved. The factors were surface cleanliness, surface wetness, upward vs. downward application, and surface voids. A common unidirectional CFRP was applied to small-scale concrete samples with factorial combinations. Ground-penetrating radar and thermography NDE methods were applied to detect possible disbonds at CFRP-concrete interfaces. Thermography was found to clearly detect all four factors, while the GPR was only effective for detecting the surface voids only. The thermal images overpredicted the amount of debonded CFRP areas by about 25%, possibly due to scaling errors between the thermograph and the sample surface. The maximum debonded CFRP area in any sample was about two percent of the total CFRP area. This is a negligible amount of debonding, showing that the factors considered are unlikely to significantly affect the laminate performance or any CFRP contribution to the concrete member strength or confinement.

scholarly journals Small-scale spatio-temporal characteristics of accumulation rates in western Dronning Maud Land, Antarctica

2008 ◽  
Vol 54 (185) ◽  
pp. 315-323 ◽  
Author(s):  
Helgard Anschütz ◽  
Daniel Steinhage ◽  
Olaf Eisen ◽  
Hans Oerter ◽  
Martin Horwath ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Temporal Variations ◽  
Spatial Variations ◽  
Small Scale ◽  
Accumulation Rates ◽  
Order Of Magnitude ◽  
Dronning Maud Land ◽  
Spatio Temporal ◽  
Ground Penetrating ◽  
Firn Core

AbstractSpatio-temporal variations of the recently determined accumulation rate are investigated using ground-penetrating radar (GPR) measurements and firn-core studies. The study area is located on Ritscherflya in western Dronning Maud Land, Antarctica, at an elevation range 1400–1560 m. Accumulation rates are derived from internal reflection horizons (IRHs), tracked with GPR, which are connected to a dated firn core. GPR-derived internal layer depths show small relief along a 22 km profile on an ice flowline. Average accumulation rates are about 190 kg m−2 a−1 (1980–2005) with spatial variability (1σ) of 5% along the GPR profile. The interannual variability obtained from four dated firn cores is one order of magnitude higher, showing 1σ standard deviations around 30%. Mean temporal variations of GPRderived accumulation rates are of the same magnitude or even higher than spatial variations. Temporal differences between 1980–90 and 1990–2005, obtained from two dated IRHs along the GPR profile, indicate temporally non-stationary processes, linked to spatial variations. Comparison with similarly obtained accumulation data from another coastal area in central Dronning Maud Land confirms this observation. Our results contribute to understanding spatio-temporal variations of the accumulation processes, necessary for the validation of satellite data (e.g. altimetry studies and gravity missions such as Gravity Recovery and Climate Experiment (GRACE)).

Study of external factors to minimize segregation of granular particles

2020 ◽  
Vol 31 (10) ◽  
pp. 2050147
Author(s):  
Saleema Panda ◽  
Danielle S Tan
Keyword(s):  
Food Processing ◽  
External Factors ◽  
Small Scale ◽  
Pharmaceutical Chemical ◽  
Wall Roughness ◽  
Related Factors ◽  
End Products ◽  
Granular Particles ◽  
Scale Experiment

Segregation of granular particles affects the quality of end products in the pharmaceutical, chemical and food processing industries. Many researchers have worked on controlling the mechanical properties of granular particles to minimize segregation. In this paper, we studied different chute-related factors — inclination angle, friction, fill, channel geometry and base profile — and their effects on segregation. We conducted a small-scale experiment with chute inclined at different angles, and also numerical simulations performed using an open-source discrete element method (DEM) code — LIGGGHTS. We found the optimal condition for minimum segregation of a binary granular mixture. We concluded that segregation is minimized if the stream-wise velocity is low, for example, by keeping the chute at a low inclination [Formula: see text] and increasing the wall roughness to 0.14.

Diffraction imaging of ground-penetrating radar data

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. H1-H12 ◽  
Author(s):  
Hemin Yuan ◽  
Mahboubeh Montazeri ◽  
Majken C. Looms ◽  
Lars Nielsen
Keyword(s):  
Ground Penetrating Radar ◽  
Field Data ◽  
Velocity Structure ◽  
Velocity Estimation ◽  
Small Scale ◽  
Imaging Method ◽  
Surface Reflection ◽  
Diffraction Imaging ◽  
Saturated Media ◽  
Ground Penetrating

Diffractions caused by, e.g., faults, fractures, and small-scale heterogeneity localized near the surface are often used in ground-penetrating radar (GPR) reflection studies to constrain the subsurface velocity distribution using simple hyperbola fitting. Interference with reflected energy makes the identification of diffractions difficult. We have tailored and applied a diffraction imaging method to improve imaging for surface reflection GPR data. Based on a plane-wave destruction algorithm, the method can separate reflections from diffractions. Thereby, a better identification of diffractions facilitates an improved determination of GPR wave velocities and an optimized migration result. We determined the potential of this approach using synthetic and field data, and, for the field study, we also compare the estimated velocity structure with crosshole GPR results. For the field data example, we find that the velocity structure estimated using the diffraction-based process correlates well with results from crosshole GPR velocity estimation. Such improved velocity estimation may have important implications for using surface reflection GPR to map, e.g., porosity for fully saturated media or soil moisture changes in partially saturated media because these physical properties depend on the dielectric permittivity and thereby also the GPR wave velocity.

scholarly journals On the Use of Microwave Holography to Detect Surface Defects of Rails and Measure the Rail Profile

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1376 ◽  
Author(s):  
Andrey Zhuravlev ◽  
Vladimir Razevig ◽  
Sergey Ivashov ◽  
Aleksey Skrebkov ◽  
Viktor Alekseev
Keyword(s):  
Experimental Data ◽  
Electromagnetic Waves ◽  
Surface Defects ◽  
Back Propagation ◽  
Surface Profile ◽  
Small Scale ◽  
Radar Images ◽  
Comparable Accuracy ◽  
Radar Measurements ◽  
Object Of Study

The use of microwave holography for detecting rail surface defects is considered in this paper. A brief review of available sources on radar methods for detecting defects on metal surfaces and rails is given. An experimental setup consisting of a two-coordinate electromechanical scanner and a radar with stepped frequency signal in the range from 22.2 to 26.2 GHz is described, with the help of which experimental data were obtained. Fragments of R24 rails with surface defects in their heads were used as the object of study. The radar images of rail defects were obtained by the described method based on back propagation of a wavefront. It is shown that polarization properties of electromagnetic waves can be used to increase the contrast of small-scale surface defects. A method of estimating rail surface profile by radar measurements is given and applied to the experimental data. Comparison of the longitudinal rail head profiles obtained by radar and by direct contact measurements showed that the radar method gives comparable accuracy.

scholarly journals Strengthening of steel member using unbonded CFRP laminates

2020 ◽  
Vol 156 ◽  
pp. 05025
Author(s):  
Fengky Satria Yoresta ◽  
Ryotaro Maruta ◽  
Genki Mieda ◽  
Yukihiro Matsumoto
Keyword(s):  
Steel Structures ◽  
Small Scale ◽  
Great Success ◽  
Adhesively Bonded ◽  
Engineering Structures ◽  
Rc Structures ◽  
Cfrp Laminates ◽  
Cfrp Composites ◽  
Steel Members ◽  
Load Carrying

Excellent mechanical and physical properties make carbon fiber reinforced polymer (CFRP) the best options for repair, retrofit, and rehabilitation of civil engineering structures. A great success on application of this material in reinforced concrete (RC) structures has attracted much attention from many researchers to develop it in combination with steel. The number of studies on the use of CFRP composites for strengthening steel structures has still been limited and needs to be more explored. To date, the research in this field has mainly focused on CFRP strengthening with adhesively-bonded technique. This paper reports an experimental study to investigate the performance of slender axial compression steel members partially strengthened with unbonded CFRP composites. The requirements for stiffener to prevent buckling occurred in stiffening region are derived from structural equilibrium conditions. Vacuum-assisted Resin Transfer Molding (VaRTM) method is adopted to form CFRP laminates in the strengthened specimens. Totally eight small scale specimens are tested, and it is clear from the test that improvement in load-carrying capacity can be achieved by using CFRP.

Test Analysis for RC Beams Strengthened with Externally Bonded Prestressed CFRP Laminates

2008 ◽  
Vol 385-387 ◽  
pp. 41-44 ◽  
Author(s):  
Shi Qi Cui ◽  
Jin Shan Wang ◽  
Zhao Zhen Pei ◽  
Zhi Liu
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Test Results ◽  
Test Analysis ◽  
Cfrp Laminates ◽  
Cfrp Sheet ◽  
Externally Bonded

Reinforced concrete beams strengthened with externally bonded CFRP sheet and prestressed CFRP are analyzed in this paper. Crack developments and displacements with curvatures for different beams are analyzed. Test results show that prestressed CFRP are able to control the development of macro cracks in concrete and prestressed CFRP is an effective method to improve the toughness of concrete, reduce strengthening cost and meanwhile enhance bearing capacity of concrete beams.

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