1,720,968 research outputs found
Effect of steel-FRP ratio and FRP wrapping layers on tensile properties of glass FRP-wrapped ribbed steel reinforcing bars
No full textOne of the many alternative methods developed to address the corrosion problem of steel reinforcements is the use of hybrid reinforcement composed of a fiber-reinforced polymer (FRP)-wrapped ribbed steel reinforcing bars. However, the number of layers and thickness of the FRP wraps on the ribbed steel core affect the mechanical properties of the glass FRP (GFRP)-steel hybrid reinforcement. In this study, in order to increase the ductility of the hybrid reinforcements, 27 types of hybrid bars were produced by wrapping E-glass fibers at an angle around the steel reinforcement using the filament winding method. The effects of steel reinforcement diameter (8, 10 and 12 mm), steel-FRP ratio and number of glass fiber layers (one, two and three layers) on the tensile properties of hybrid reinforcement were investigated. The experimental results on hybrid bars were compared to the respective values of the plain GFRP and carbon FRP (CFRP) reinforcing bars as well as the results on hybrid bars in the literature. In addition, a theoretical stress-strain model was proposed for the GFRP-wrapped steel reinforcing bar. The study showed that increasing the FRP ratio in the hybrid reinforcement increased the ductility of the reinforcement, although the yielding stress was reduced. The strain of glass-wrapped ribbed steel reinforcements under maximum stress varied between 4.14 and 6.22%. The energy absorption capacity of the GFRP-wrapped reinforcement was observed to be higher than that of the plain GFRP, CFRP and the other hybrid bars. In addition, the developed theoretical model was found to be compatible with the experimental results
Development length and bond strength equations for FRP bars embedded in concrete
No full textKalkan, Ilker/0000-0002-5987-631XThe present study pertains to the linear multiple regression analyses on a database of 185 hinged-beam experiments on FRP bars. The database was compiled from 51 tests conducted within the scope of the present study and 134 tests conducted by previous researchers. Bond strength and development length equations, taking different types of FRP bars and surface finishes into account, were developed and the estimates from the proposed equations were compared to the estimates from the respective equations of various international FRP-reinforced concrete codes. The proposed equations, addressing all kinds of FRP bars and surface finishes, were shown to be in much closer agreement with the experimental results compared to all previous equations according to different statistical evaluation criteria, i.e. the Coefficient of Determination, Root Mean Square Error and Mean Absolute Percentage Error. The code equations were established to yield to exteremely over-conservative and non-economical results in all types of FRP bars with different surface textures.Scientific Research Unit of Kirikkale UniversityKirikkale University [2018/014]The present paper is a summary of a portion of the Ph.D. dissertation conducted by Dr. Bogachan Basaran under the supervision of Assoc. Prof. Dr. Ilker Kalkan at the Department of Civil Engineering, Kirikkale University. The tests within the scope of the study were conducted at the Structural Mechanics Laboratory of the Vocational School of Technical Sciences of Amasya University. The financial support provided by the Scientific Research Unit of Kirikkale University through the project number 2018/014 is gratefully acknowledged. The authors also express gratitude to Prof. Dr. Sabahattin Aykac at the Department of Civil Engineering, Gazi University for his valuable comments and contribution throughout the course of study
Investigation on variables affecting bond strength between FRP reinforcing bar and concrete by modified hinged beam tests
No full textKalkan, Ilker/0000-0002-5987-631XAbstract
The bond strength between FRP reinforcement and concrete significantly affects the load bearing capacity and deformation ability of an FRP reinforced concrete member subjected to bending. There are numerous parameters affecting this bond. In the past, however, studies of FRP rebar-concrete bond strength have considered only one or more of the basalt, glass and carbon FRP reinforcement types, and generally only one or a limited number of surface properties. Since all variables affecting this bond were not set forth, experiments were not conducted on the basis of keeping other test variables constant to examine the effect of a single parameter. In this study, in order to conduct a proper experimental study on concrete-FRP bond by isolating a single parameter in the related tests, 90 hinged beam tests were carried out under transverse loading. The effects of reinforcement fiber type (basalt, glass, carbon), reinforcement surface property (ribbed, wrapped, wounded, sand coated), distance between rebars, bottom and side concrete cover, reinforcement diameter, reinforcement embedment length, presence of stirrups, concrete compressive strength on FRP -concrete bond strength were investigated. Experiments conducted within the scope of this study showed that the effects of concrete compressive strength and concrete cover (bottom and side) on this bond are limited. Moreover, the bond strength values of rebars with mechanical interlocking load-bearing mechanism were found to be higher than the respective values of the ones with friction mechanism. Finally, an increase in the modulus of elasticity of FRP resulted in an increase in bond strength and the presence of stirrups in the beams reduced the bond strength.Kirikkale UniversityKirikkale University [2018/014]The present paper is a condensation of a portion of the Ph.D. thesis of Dr. Bogachan Basaran under the supervision of Dr. Ilker Kalkan. The study was supported by Kirikkale University Scientific Research Project Coordination Unit under the project number 2018/014. This support is gratefully acknowledged. The experiments were conducted in the Structural Mechanics Laboratory of the Technical Sciences Vocational School, Amasya University
FRP donatı-beton aderansı deney yöntemlerinin aderansı etkileyen değişkenlere göre karşılaştırılması
No full textThere are many test methods in the international testing standards for the evaluation of FRP reinforcement-concrete bond. However, differences in test conditions of these methods affect FRP reinforcement-concrete bond. Therefore, even in the tests with identical test parameters, different bond strength values are attained due to experimental differences. In this study, the factors affecting FRP reinforcement-concrete bond were determined individually for four different test methods (hinged beam, beam-end, spliced beam and pullout tests) by using the gauss process regression (GPR) method. Accordingly, eight parameters affecting the bond strength, namely the diameter, fiber type, surface texture, embedment length, location in concrete and clear cover of reinforcement, the concrete compressive strength and the presence and degree of confining by means of transverse reinforcement were adopted as test parameters. In this way, the effects of each variable on bond strength were investigated for each test method and the methods were compared in terms of each parameter. The analyses on the four methods for identical test parameters depicted that there were differences in bond strength values as great as four times from one test method to another. The average bond strength values from the hinged beam tests were about 31, 3 and 146 % higher than the respective values from the pullout tests, beam-end tests and spliced beam tests, respectively. The degree of influence of each parameter on bond strength was established to depend on the test method and the same parameter was found to even have opposite effects on bond strength in different test methods
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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