1,721,072 research outputs found
Micro-mechanical FE numerical model for masonry curved pillars reinforced with FRP strips subjected to single lap shear tests
Full text linkThe present paper discusses the results obtained by using a micro-mechanical FE numerical model for the study the bond behavior of some curved specimens strengthened by Fiber Reinforced Polymer (FRP) composite materials. The numerical model, implemented into the FE code Abaqus, is a sophisticated micro-modelling (heterogeneous) approach, where bricks and mortar are meshed separately by means of 4-noded plane strain elements exhibiting distinct damage in tension and compression, FRP is assumed elastic and an elastic uncoupled cohesive layer is interposed between FRP reinforcement and masonry pillar. The experimental investigation considered to benchmark the numerical approach is aimed at characterizing the influence of normal stresses induced by curved supports on the stress-transfer mechanism of FRP materials. To this scope some single lap shear tests performed at the University of Florence on FRP reinforced curved pillars with two different curvature radii (1500 and 3000 mm) are here considered. The obtained numerical results show a promising match with experimental evidences, in terms of elastic stiffness, peak loads and post-peak behavior. Indeed, the proposed approach allows to correctly account for important local effects, such as the effect of FRP-masonry interfacial normal stresses on the global delamination strength and the distribution of damage in the pillar volume. By using the proposed modelling approach, comprehensive numerical sensitivity analyses to investigate the role played by the curvature on the ultimate delamination strength, are also presented in the paper
The influence of the joint thickness on the adhesion between CFRP reinforcements and masonry arches
No full textThe effectiveness of Carbon Fiber Reinforced Polymers (CFRP) reinforcements bonded to masonry structures is demonstrated by the several interventions made on existing buildings as well as by the numerous studies presented in the scientific literature. In practical strengthening interventions, CFRP sheets are being used to reinforce both plane and curved structural elements. Contrariwise, research in the scientific literature are mainly devoted to the analysis of the effectiveness of such reinforcements bonded on plane surfaces. For this reason, the experimental program described in this paper concerns the analysis of the mechanical behavior of portion of masonry arches reinforced by CFRP sheets. The experimental results allowed to analyze the effectiveness of such reinforcements applied at intrados or extrados, loaded by actions tangent to an end of the reinforcement itself. The influence of the mortar joints thickness on the performance of such reinforcements has been also analyzed in the experimental program
Coupled interface-based modelling approach for the numerical analysis of curved masonry specimens strengthened by CFRP
Full text linkAim of the present paper is to numerically study the bond behavior of curved masonry specimens externally strengthened by Carbon Fiber Reinforced Polymer systems (CFRP). A simple 1D-modeling approach is presented to this aim, where the coupled behavior between shear and normal stresses developing at the reinforcement/masonry interface level is specifically introduced to properly account for the role played by the curvature radius. The model is indeed enriched by the introduction of shear stress-slip laws able to account for the beneficial friction effect, when compression normal stresses develop at the interface level and the reduction of the slip strength corresponding to the de-cohesion in presence of normal stresses in tension. Considering some case studies derived from the current literature, consisting of shear-lap bond tests of curved masonry specimens characterized by different curvatures of the bonded surface and different strengthening configurations, the validation of the proposed approach is carried out. In particular, two modeling strategies are considered and critically compared: the first one, denoted as approach (A), where the presence of the mortar joints is neglected, and the second one, denoted as approach (B), where mortar joints are specifically introduced in the model. Finally, the results obtained by using the proposed simple approach are compared with those obtained from both sophisticated FE numerical models and theoretical formulas deduced from the current literature
Delamination of FRP reinforced curved masonry pillars: Experimentation and advanced numerical analyses
No full textThe present paper discusses the experimental results obtained testing some curved specimens strengthened using Fiber Reinforced Polymer (FRP) composite materials. The experimental investigation has been aimed at characterizing the influence of normal stresses induced by curved supports on the stress-transfer mechanism of FRP composites. To this scope some single lap shear tests performed at the University of Florence on FRP strengthened curved prisms with two different curvature radii (1500 and 3000 mm) have been analyzed. The numerical model, implemented in the FE code Abaqus, is a sophisticated micro-modeling (heterogeneous) approach, where bricks and mortar are simulated separately with 4-noded plane strain elements with damage in tension and compression, FRP is assumed elastic and an elastic uncoupled cohesive layer is placed between FRP reinforcement and the masonry support. Numerical results obtained are in satisfactory agreement with the experimental ones in terms of peak loads, collapse mechanisms and damage patterns at collapse. A detailed investigation of the effect of FRP-masonry normal stresses is also present in the proposed paper
Weathering action on thermo-viscoelastic properties of polymer interlayers for laminated glass
Full text linkMechanical properties of interlayer polymers are recognized to be essential for a correct design of lam-
inated glass structures. Although several researches have been carried out on the consequences of weath-
ering actions on a laminated glass, few quantitative data on the properties of polymers are available. The
response of structures to a long duration load is therefore evaluated taking into account the effects of vis-
cosity of the interlayer, but in the hypothesis that the interlayer material does not degrade over time. In
this paper the results are reported of an experimental analysis of the thermo-viscoelastic properties of
polyvinyl butyral used as interlayer of laminated glass, subjected to weathering actions (humidity, ther-
mal cycles and UV radiation). The results were interpreted in the light of the connection between
microstructure and rheology of polymers, and highlight two different damage mechanisms, promoted
in different extents by the different weathering actions
Test Methods for the Determination of Interlayer Properties in Laminated Glass
Full text linkCurrent standards introduce different test methods to be used for the determination of the dynamic properties of polymers. Some
of these have been applied in the last years for the evaluation of the thermoviscoelastic properties of interlayer in laminated glass. Even the
latest draft standards, which provide test methods for the determination of mechanical properties of laminated glass interlayers, hesitate
in providing a definite test procedure and thus allow the use of three different test methods depending on the kind of interlayer. Here,
a short review of the test methods collected from the literature is proposed and some considerations are made regarding their strengths
and weaknesses. The scope of studies surveyed does not claim to be exhaustive, but simply to be representative of the variety of procedures
employed in research. The necessity is stressed to converge to as limited a number of test methods as possible that are also adequately simple
and can therefore be applied in most research laboratorie
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
Single lap shear tests of masonry curved pillars externally strengthened by CFRP strips
Full text linkThe paper presents an experimental study concerning the bond behaviour of Carbon Fiber Reinforced Polymers (CFRP) sheet reinforcements applied to curved masonry surfaces. Such strengthening technique is more and more used in structural rehabilitation and retrofitting of existing buildings. Its effectiveness has been demonstrated by several studies published in the literature, mostly devoted to flat bonded surfaces. Observing that CFRPs are extensively applied on arches and vaults but only few research activities concern curved bonded surfaces, the experimental study described in this paper is aimed to contribute to fill this gap. The experimental program was carried out on portions of masonry arches, reinforced by CFRP sheets bonded at extrados or intrados, tested by a single lap shear test. The experimental results allowed to analyse the effectiveness of such reinforcements, loaded by actions tangent to an end of the reinforcement itself, with respect to its position (intrados or extrados) and to the curvature of the bonding surface. As expected, the results highlight that the bond behaviour strongly depend on the position of the reinforcement. In particular, the capacity of reinforcements bonded at the extrados increases with the curvature, while decreases with the curvature for those bonded at intrados
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