The Experts below are selected from a list of 27510 Experts worldwide ranked by ideXlab platform
Joaquim A. O. Barros - One of the best experts on this subject based on the ideXlab platform.
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experimental study on bond performance of gfrp bars in self compacting steel fiber reinforced concrete
Composite Structures, 2013Co-Authors: Hadi Mazaheripour, Jose Senacruz, Marco Pepe, Joaquim A. O. Barros, Enzo MartinelliAbstract:Abstract Reinforcing bars made of Glass-Fiber-Reinforced Polymers (GFRPs) are more and more common as internal reinforcement of concrete structures and infrastructures. Since the design of GFRP reinforced concrete members is often controlled by serviceability limit state criteria (i.e. deflection or crack width control), an accurate knowledge of the GFRP-concrete bond behavior is needed to formulate sound design equations. Furthermore, bond laws currently available and widely accepted for conventional steel rebars cannot be straightforwardly applied for GFRP ones. Hence, an experimental program consisting of 36 pullout bending tests was carried out to evaluate the bond performance between GFRP bars and steel fiber reinforced self-compacting concrete (SFRSCC) by analyzing the influence of the following parameters: GFRP bar diameter, surface characteristics of the GFRP bars, bond length, and SFRSCC Cover Thickness. Based on the results obtained in this study, pullout failure was occurred for almost all the specimens. SFRSCC Cover Thickness and bond length plaid important role on the ultimate value of bond stress of GFRP bars. Moreover, the GFRP bars with ribbed and sand-coated surface treatment showed different interfacial bond behaviors.
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flexural and shear strengthening of rc beams with composite materials the influence of cutting steel stirrups to install cfrp strips
Cement & Concrete Composites, 2010Co-Authors: Ines Costa, Joaquim A. O. BarrosAbstract:Abstract Experimental, numerical and analytical investigations have revealed that Carbon Fibre Reinforced Polymer (CFRP) strips with larger cross section height improve the effectiveness of the Near Surface Mounted (NSM) technique for the flexural strengthening of existing reinforced concrete (RC) beams. However, this height is limited to the concrete Cover Thickness of the longitudinal steel bars, since the application of strips of cross section height larger than the Cover Thickness requires that the bottom arm of the steel stirrups be cut. This work aims to assess the influence, in terms of shear resistance, of cutting the bottom arm of steel stirrups to install NSM strips for the flexural strengthening of RC beams. The obtained results showed that, for monotonic loading, cutting the bottom arm of steel stirrups led to a decrease of the beam’s load carrying capacity of less than 10%. Due to the high effectiveness of the adopted NSM flexural strengthening systems, shear can be a predominant failure mode for these beams. To avoid this type of failure mode, strips of wet lay-up CFRP sheets with U configuration were used, resulting in effective strengthening solutions for RC beams. In the present paper the experimental program is described, and the obtained results are presented and discussed.
Leila Cristina Meneghetti - One of the best experts on this subject based on the ideXlab platform.
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chloride accelerated test influence of silica fume water binder ratio and concrete Cover Thickness
Revista IBRACON de Estruturas e Materiais, 2013Co-Authors: Elias Pereira, A Resende, M H F De Medeiros, Leila Cristina MeneghettiAbstract:In developed countries like the UK, France, Italy and Germany, it is estimated that spending on maintenance and repair is practically the same as investment in new constructions. Therefore, this paper aims to study different ways of interfering in the corrosion kinetic using an accelerated corrosion test - CAIM, that simulates the chloride attack. The three variables are: concrete Cover Thickness, use of silica fume and the water/binder ratio. It was found, by analysis of variance of the weight loss of the steel bars and chloride content in the concrete Cover Thickness, there is significant influence of the three variables. Also, the results indicate that the addition of silica fume is the path to improve the corrosion protection of low water/binder ratio concretes (like 0.4) and elevation of the concrete Cover Thickness is the most effective solution to increase protection of high water/binder ratio concrete (above 0.5).
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chloride accelerated test influence of silica fume water binder ratio and concrete Cover Thickness ensaio acelerado por cloretos efeito da silica ativa relacao agua aglomerante e espessura de cobrimento do concreto
2013Co-Authors: Elias Pereira, A Resende, M H F De Medeiros, Leila Cristina MeneghettiAbstract:In developed countries like the UK, France, Italy and Germany, it is estimated that spending on maintenance and repair is practically the same as investment in new constructions. Therefore, this paper aims to study different ways of interfering in the corrosion kinetic using an accelerated corrosion test – CAIM, that simulates the chloride attack. The three variables are: concrete Cover Thickness, use of silica fume and the water/ binder ratio. It was found, by analysis of variance of the weight loss of the steel bars and chloride content in the concrete Cover Thickness, there is significant influence of the three variables. Also, the results indicate that the addition of silica fume is the path to improve the corrosion protection of low water/binder ratio concretes (like 0.4) and elevation of the concrete Cover Thickness is the most effective solution to increase protection of high water/binder ratio concrete (above 0.5).
Stephen F Ackley - One of the best experts on this subject based on the ideXlab platform.
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Thickness distribution of antarctic sea ice
Journal of Geophysical Research, 2008Co-Authors: A P Worby, Cathleen A Geiger, Matthew J Paget, Michael Van Woert, Stephen F Ackley, Tracy L DelibertyAbstract:[1] Ship-based observations are used to describe regional and seasonal changes in the Thickness distribution and characteristics of sea ice and snow Cover Thickness around Antarctica. The data set comprises 23,373 observations collected over more than 2 decades of activity and has been compiled as part of the Scientific Committee on Antarctic Research (SCAR) Antarctic Sea Ice Processes and Climate (ASPeCt) program. The results show the seasonal progression of the ice Thickness distribution for six regions around the continent together with statistics on the mean Thickness, surface ridging, snow Cover, and local variability for each region and season. A simple ridge model is used to calculate the total ice Thickness from the observations of level ice and surface topography, to provide a best estimate of the total ice mass, including the ridged component. The long-term mean and standard deviation of total sea ice Thickness (including ridges) is reported as 0.87 ± 0.91 m, which is 40% greater than the mean level ice Thickness of 0.62 m. Analysis of the structure function along north/south and east/west transects revealed lag distances over which sea ice Thickness decorrelates to be of the order of 100–300 km, which we use as a basis for presenting near-continuous maps of sea ice and snow Cover Thickness plotted on a 2.5 � 5.0 grid.
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wave rafting and the equilibrium pancake ice Cover Thickness
Journal of Geophysical Research, 2004Co-Authors: Mingrui Dai, Hayley H Shen, Mark A Hopkins, Stephen F AckleyAbstract:[1] Pancake ice, the circular floes formed during ice growth in a wave field, forms in many polar and subpolar seas. Vertical thin sections of cores taken from the ice Cover in these regions show distinct layering structure. These observations suggest wave rafting could play a significant role in defining the ice Cover Thickness, much more so than thermodynamic growth. Although wave rafting is intuitively apparent, no previous study relating the resulting ice Cover to wave characteristics has been conducted. In this study we utilize both laboratory experiments and numerical simulations to determine the rafting process. We propose a theory that predicts a final equilibrium Thickness, provided that the incoming wave is kept constant. The equilibrium Thickness from the theory is proportional to the square of the wave amplitude and the square of the floe diameter and is inversely proportional to the cube of the wavelength. This theory relates the final ice Cover Thickness to the wave characteristics and the size and surface properties of the pancake ice floes. This theory also provides a way to calculate the speed with which the boundary between the single-layer pancake ice floes and the equilibrium rafted ice Cover propagates. We conduct laboratory experiments with plastic model pancake ice to create rafting. We perform computer simulations with a three-dimensional discrete element model that simulates the movement of disc-shaped floes in the wave field. We compare the theoretical result with the laboratory experiments and a numerically simulated rafting process. Both the laboratory and the computer simulation results compare favorably with the theory.
Enzo Martinelli - One of the best experts on this subject based on the ideXlab platform.
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experimental study on bond performance of gfrp bars in self compacting steel fiber reinforced concrete
Composite Structures, 2013Co-Authors: Hadi Mazaheripour, Jose Senacruz, Marco Pepe, Joaquim A. O. Barros, Enzo MartinelliAbstract:Abstract Reinforcing bars made of Glass-Fiber-Reinforced Polymers (GFRPs) are more and more common as internal reinforcement of concrete structures and infrastructures. Since the design of GFRP reinforced concrete members is often controlled by serviceability limit state criteria (i.e. deflection or crack width control), an accurate knowledge of the GFRP-concrete bond behavior is needed to formulate sound design equations. Furthermore, bond laws currently available and widely accepted for conventional steel rebars cannot be straightforwardly applied for GFRP ones. Hence, an experimental program consisting of 36 pullout bending tests was carried out to evaluate the bond performance between GFRP bars and steel fiber reinforced self-compacting concrete (SFRSCC) by analyzing the influence of the following parameters: GFRP bar diameter, surface characteristics of the GFRP bars, bond length, and SFRSCC Cover Thickness. Based on the results obtained in this study, pullout failure was occurred for almost all the specimens. SFRSCC Cover Thickness and bond length plaid important role on the ultimate value of bond stress of GFRP bars. Moreover, the GFRP bars with ribbed and sand-coated surface treatment showed different interfacial bond behaviors.
Shiyin Liu - One of the best experts on this subject based on the ideXlab platform.
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impact of varying debris Cover Thickness on ablation a case study for koxkar glacier in the tien shan
The Cryosphere, 2014Co-Authors: M Juen, Christoph Mayer, A Lambrecht, H Han, Shiyin LiuAbstract:To quantify the ablation processes on a debris Covered glacier, a simple distributed ablation model has been developed and applied to a selected glacier. For this purpose, a set of field measurements was carried out to collect empirical data. A morphometric analysis of the glacier surface enables us to capture statistically the areal distribution of topographic features that influence debris Thickness and consequently ablation. Remote-sensing techniques, using high-resolution satellite imagery, were used to extrapolate the in situ point measurements to the whole ablation area and to map and classify melt-relevant surface types. As a result, a practically applicable method is presented that allows the estimation of ablation on a debris Covered glacier by combining field data and remote-sensing information. The sub-debris ice ablation accounts for about 24% of the entire ice ablation, while the percentage of the moraine Covered area accounts for approximately 32% of the entire glacierized area. Although the ice cliffs occupy only 1.7% of the debris Covered area, the melt amount accounts for approximately 12% of the total sub-debris ablation and 2.5% of the total ablation respectively. Our study highlights the influence of debris Cover on the response of the glacier terminus in a particular climate setting. Due to the fact that melt rates beyond 0.1 m of moraine Cover are highly restricted, the shielding effect of the debris Cover dominates over the temperature and elevation dependence of the ablation in the bare ice case.
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impact of varying debris Cover Thickness on ablation a case study for koxkar glacier in the tien shan sci
2014Co-Authors: M Juen, Christoph Mayer, A Lambrecht, H Han, Shiyin LiuAbstract:To quantify the ablation processes on a debris Covered glacier, a simple distributed ablation model has been developed and applied to a selected glacier. For this purpose, a set of field measurements was carried out to collect empirical data. A morphometric analysis of the glacier surface enables us to capture statistically the areal distribution of topographic features that influence debris Thickness and consequently ablation. Remote-sensing techniques, using high-resolution satellite imagery, were used to extrapolate the in situ point measurements to the whole ablation area and to map and classify melt-relevant surface types. As a result, a practically applicable method is presented that allows the estimation of ablation on a debris Covered glacier by combining field data and remote-sensing information. The sub-debris ice ablation accounts for about 24% of the entire ice ablation, while the percentage of the moraine Covered area accounts for approximately 32% of the entire glacierized area. Although the ice cliffs occupy only 1.7% of the debris Covered area, the melt amount accounts for approximately 12% of the total sub-debris ablation and 2.5% of the total ablation respectively. Our study highlights the influence of debris Cover on the response of the glacier terminus in a particular climate setting. Due to the fact that melt rates beyond 0.1m of moraine Cover are highly restricted, the shielding effect of the debris Cover dominates over the temperature and elevation dependence of the ablation in the bare ice case.
