1,720,967 research outputs found
Direct and semi-direct ultrasonic testing for quality control of FRC-concrete adhesion
Full text linkExternally bonded Fiber Reinforced Composite (FRC) materials, such as Fiber Reinforced Polymers (FRP) and Fiber Reinforced Cementitious Matrix (FRCM), have been increasingly used over the last decades for retrofitting existing structural elements due to their excellent mechanical and physical properties. However, the effectiveness of the reinforcement depends on the quality of the adhesion between the reinforcement and its substrate. The present paper reports the results of an experimental campaign in which the Ultrasonic Pulse Velocity (UPV) testing has been applied to detect the presence of adhesion defects at the interface FRC-concrete. UPV has been carried out on concrete specimens strengthened with different types of FRC. Some inclusions have been specifically placed at the interface between the reinforcement and the concrete to simulate adhesion defects. UPV has been applied both in the direct and in the semi-direct mode, to simulate different realistic on-site situations, including the possible inaccessibility of some parts of the element to check. Results show that UPV, applied by means of both direct and semi-direct modes, allows to identify the presence of adhesion defects, and evoke the possibility of discriminating between different defects
Concrete Defects Sizing by Means of Ultrasonic Velocity Maps
Full text linkThe paper illustrates the results of an experimental test which intends to check the efficacy of ultrasonic testing (UT) in detecting anomalies inside concrete elements. For this purpose, UT has been carried out on a small concrete wall having different defects deliberately settled inside the wall during casting. A grid of several measurements points has been arranged on the wall surfaces and for each point the ultrasonic signal has been acquired after passing through the thickness of the wall and the propagation velocity V has been extracted and analyzed. A graphic representation of V distribution has been implemented by a map where each pixel identifies one measurement point and is representative of its neighborhood. This map highlights areas with different velocity values, and allows to visually detect areas having particularly low velocity. The matching between the low-velocity areas and the artificial defects has been analyzed, and the level of accuracy of the V map in detecting and sizing the concrete inner defects has been discussed with reference to different spacing of the grid points. Finally, some considerations regarding the choice of the most suitable measurements grid have been addressed
Grading of low quality wood for use in structural elements
No full textTimber is a sustainable resource, environmentally friendly and aesthetically pleasing. Using locally grown timber as building material leads to economic, social and environmental benefits. Being an organic material, timber is not homogeneous; hence, it is crucial to predict the base material quality. International codes require the use of wood previously graded according to the current regulations in order to verify its reliability when used as structural material. An exhaustive analysis of the state of art of different methodologies and code requirements for structural timber grading is presented herein. Structural timber grading methods and their applicability to low-strength timber is analysed and discussed with reference to Maritime Pine locally grown in Sardinia (Italy). Several physical and morphological parameters such as density, the presence of knots, clusters of knots, grain deviation, warping, annual ring width and moisture content had to be measured. Moreover, mechanical parameters (tensile strength and modulus of elasticity in tension) were measured and analysed in order to identify the strength class of Sardinian Maritime Pine. The operational issues related to the application of the different methodologies and code requirements for structural grading of low-quality wood are also discussed and analysed
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
Strength class prediction of Sardinia grown timber by means of non destructive parameters
No full textIn Italy timber and wood products are becoming increasingly used for building
constructions due to their excellent physics and mechanical properties. International Codes require
the use of wood previously graded according to the current regulation. This paper reports the preliminary results of an experimental campaign aimed at verifying the reliability of the use of
Sardinian timber as structural material. For this purpose Maritime Pine boards from two different Sardinian areas have been analyzed and visual strength graded. Physical and morphological
properties (density, knots, clusters knot, resin pockets, deviation of the grain, annual ring width position of board respect to the pith, humidity, etc.) along with mechanical and non destructive
properties (elastic modulus, tensile strength, sonic pulse velocity) have been checked. Timber properties have been statistically evaluated in order to identify the performance of the base material. Regression analyses have been carried out by studying the correlation between non destructive
parameters and mechanical properties in order to define a criterion for predicting the strength class of the base material
Comparison between calculated and measured performances of impact sound insulation for Cross Laminated Timber building elements
No full textThe use of simplified prediction models described in the EN 12354 series standard is largely diffused and suggested or adopted in many building codes. The aim of this work is to evaluate the reliability of calculation methods of impact sound insulation by comparison with in situ measurements. A case study about buildings made with Cross Laminated Timber (CLT) elements is presented
Comparison between calculated and measured performances of impact sound insulation for Cross Laminated Timber building elements
No full textThe use of simplified prediction models described in the EN 12354 series standard is largely
diffused and suggested or adopted in many building codes. The aim of this work is to evaluate the
reliability of calculation methods of impact sound insulation by comparison with in situ
measurements. A case study about buildings made with Cross Laminated Timber (CLT) elements
is presented
- …
