1,720,957 research outputs found
Compressive Behavior of Masonry Columns Confined with Multi-layer SRG Composite
No full textSteel-reinforced grout (SRG) is a type of composite used for structural strengthening applications. SRG is comprised of high-strength steel cords embedded in an inorganic matrix. In this paper, the results of an experimental study carried out to understand the compressive behavior of masonry columns confined by multi-layer SRG jackets are presented. Twenty-four confined and seven unconfined solid fired-clay brick masonry columns with a square cross-section were tested to failure under a concentric compressive load. Test parameters included the column corner condition, number of fiber sheet layers, and number of column faces the fiber sheets were overlapped (in the wrap direction), referred to herein as the number of fiber overlapping faces. SRG confinement was found to improve the compressive strength, ultimate axial strain, and energy absorption of the masonry columns. Results showed that the confined compressive strength, ultimate strain, and absorbed energy increased with the number of fiber sheet layers, however the increase in confined strength was not proportional to the number of fiber sheet layers. Rounding the column corners slightly increased the confined compressive strength. Increasing the number of fiber overlapping faces also increased the confined compressive strength, ultimate strain, and absorbed energy
A Discussion of Differences Between Single-Lap Tests and Full-Scale Beam Tests in Terms of FRCM-Concrete Debonding
No full textFiber-reinforced cementitious matrix (FRCM) composites are a recent addition to the family of fiber-reinforced composites employed as externally-bonded reinforcement to strengthen reinforced concrete members. FRCM composites use a cementitious matrix rather than epoxy, which is typically used for the well-known fiber-reinforced polymer (FRP) composites. For both FRCM and FRP, the weakness of the technology is the premature debonding of the composites, which in most cases is a brittle phenomenon. The study of the debonding is often carried out at the small-scale level by employing small blocks of concrete with a strip of composite applied to one face. Different set-ups exist to study the phenomenon at the small scale. The most common set-up is the pull-push single-lap direct-shear test, in which the composite strip is pulled while the concrete block is restrained in such a way that the interfaces between the composite and the block is subjected mainly to shear stresses. The set-up is designed to represent the shear stress-transfer that occurs at the composite-concrete interface in full-scale strengthened beams.Single-lap direct-shear tests are commonly used to study the debonding phenomenon because the specimens are easy to construct and handle, especially compared to full-scale beams. Nevertheless, the open question in the scientific community is whether the results of single-lap direct-shear tests can provide useful information on the debonding phenomenon in strengthened beams. This paper aims at providing an insight into this open question. The paper focuses on single-lap shear tests and full scale beam tests that employ a polyparaphenylene benzo-bisoxazole (PBO) FRCM composite
A Comparative Study of Bond Test Methods for Externally Bonded FRCM and SRG Composites
No full textThe bond behavior of externally-bonded fiber reinforced composites has been studied experimentally using different types of test methods. In this study the bond behavior of composite strips externally bonded to fired-clay brick masonry was tested using single-lap direct shear tests and hinged beam tests. The results obtained from the two test types were compared to investigate the effect of the test set-up on the load-carrying capacity of the matrix-fiber interface. Two different composite systems were considered: a fiber-reinforced cementitious matrix (FRCM) composite with a balanced bidirectional mesh of basalt fibers embedded in a hydraulic lime-based mortar, and a steel reinforced grout (SRG) with a sheet of ultra-high-strength unidirectional steel fiber cords embedded in the same mortar. The results are discussed and compared in terms of failure modes and applied load versus slip of the fibers response. An estimate of the matrix-fiber interfacial fracture energy of SRG-masonry joints is proposed using a global energy balance approach that does not require measurement of the strain in the fibers
Analytical Bond-Slip Model for Fiber-Reinforced Cementitious Matrix-Concrete Joints Based on Strain Measurements
No full textAn accurate bond-slip model is of fundamental importance to analyze the response of fiber-reinforced cementitious matrix (FRCM) composite-strengthened structures. This study proposes a method to determine the bond-slip model of FRCM-concrete joints based on longitudinal fiber strains. First, discrete strain profiles measured with strain gauges were fitted by a continuous function ε(y), where y is the coordinate along the bonded length. Then the slip s(y) and shear stress τ (y) along the composite bonded length were obtained by integration and derivation of ε(y), respectively. The debonding load and peak load from single-lap direct shear specimens were predicted by the fitted function ε(y) and showed good agreement with test results. From the plot of the τ(s) relationship obtained from ε(y), an alternative, closed- form, continuous bond-slip relationship was obtained based on the maximum shear stress τm and the corresponding slip sm. The fracture energy was compared for both relationships and was in reasonable agreement with values reported in previous studies
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
Three-Dimensional Numerical Modeling of Single-Lap Direct Shear Tests of FRCM-Concrete Joints Using a Cohesive Damaged Contact Approach
No full textThe bond behavior of fiber-reinforced cementitious matrix (FRCM) composites applied as externally bonded reinforcement is the most critical concern in this type of application. FRCM-concrete joints are generally reported to fail because of debonding (slippage) of the fibers from the embedding matrix. However, depending on the characteristics of the composite and substrate used, failure may also occur as a result of detachment of the composite strip at the FRCM-support interface, interlaminar failure (delamination) of the matrix, or tensile failure of the fibers. In this paper, a three-dimensional (3D) numerical model is developed to reproduce the behavior of polyparaphenylene benzo-bisoxazole (PBO) FRCM-concrete joints. The numerical model accounts for the fracture mechanics mixed Mode-I and Mode-II loading condition observed in single-lap direct shear tests by means of nonlinear damaged contact law associated with different interfaces considered in the analysis. The numerical results obtained are compared with those obtained by experimental tests of PBO FRCM-concrete joints. The model is capable of predicting the different failure modes, and it correctly reproduces the experimental load responses including the contribution of friction to the applied stress
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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