1,720,985 research outputs found
Experimental Characterization of Fabric-Reinforced Cementitious Matrix (FRCM) Systems Applied on Calcarenite Stone: Adoption of Non-Standard Setup for Double-Shear Bond Tests
Full text linkThe use of Fabric-Reinforced Cementitious Matrix (FRCM) systems is an innovative method
for strengthening structures, particularly masonry, while addressing environmental and economic
concerns. Despite their widespread use, characterizing FRCM composites poses challenges due to
their complex mechanical behavior and considerable variability in properties. The available standardized
testing methods exhibit some inconsistencies, underscoring the need for reliable characterization
procedures. This paper presents an experimental study on the bond behavior between FRCM materials
and calcarenite stone using a non-standard setup for double shear bond tests. Different FRCM
systems are considered, varying the matrix composition and fabric nature. The experimental results
are evaluated in terms of maximum stress, slip and data dispersion, alongside comparisons with
double shear tests on larger samples and single-lap shear. These findings provide insights into how
the mortar nature influences the stress-slip curves, strength, ductility and failure modes. The experimental
study demonstrates the repeatability and robustness, particularly in terms of peak strength,
of the non-standard setup configuration utilized in the study. The study highlights the importance of
reliable characterization procedures for FRCM materials, especially in bond behavior assessments,
emphasizing the need for further research to enhance our understanding of their application in
structural reinforcement
Integrating Plastic Waste into Concrete: Sustainable Solutions for the Environment
Full text linkPlastic waste management has received significant attention in recent decades due to the urgent global environmental crisis caused by plastic pollution. The versatile and durable nature of plastic has led to its widespread usage across various sectors. However, its nonbiodegradable nature contributes to unsustainable production practices, leading to extensive landfill usage and posing threats to marine ecosystems and the food chain. To address these environmental concerns, numerous challenges have been recently addressed through investigating alternative approaches for disposing of plastic waste, with the construction sector emerging as a promising option. Incorporating plastic waste materials into concrete not only offers economic benefits but also provides a valid alternative to conventional disposal methods. This paper presents the results of different experimental studies, some of them available in the literature and others new, discussing the feasibility of integrating plastic waste into concrete and its impact on mechanical properties. The influence of different sizes, natures, treatments, and percentages of plastic waste in the concrete mixtures is dealt with in order to provide further data for helping to understand the nonunivocal results in the literature, under the conviction that only further observations can help to understand the mechanics of concrete with plastic aggregates. The experimental investigation highlighted that one parameter that is better than others and can be considered to compare different experimental investigations is the variation in weight (due to the effective volume of plastics in the mix), determining a sort of increasing of porosity that degrades the mechanical characteristics. However, this seems inconsistent in some cases. Therefore, the need for further research is highlighted to refine production methods and optimize mix designs
Monte Carlo analysis of masonry structures under tsunami action: Reliability of lognormal fragility curves and overall uncertainty prediction
Full text linkTsunami vulnerability of coastal buildings has gained more and more interest in recent years, in the consciousness of what losses may be caused. The improvement of the available approaches for the quantitative estimation of the probability of building damage and for defining possible strategies for risk mitigation is an actual goal. In this framework, several authors have provided empirical fragility curves based on field surveys after tsunamis. Nevertheless, a predictive approach based on analytical fragility curves, which can be extended to many classes of buildings, is essential for the scopes of civil protection and risk mitigation. In this paper, an approach for the construction of fragility curves, proposed for masonry structures under tsunami waves, is discussed and refined in the part regarding the assignment of the uncertainties. Further, an assessment of the reliability of the lognormal fragility distribution is carried out based on a Monte Carlo simulation applied to 4 classes of buildings. Here, it is shown that Monte Carlo analysis allows a direct evaluation of the uncertainties without the need to resort to ambiguous regression analyses and rules of combination of the uncertainties of demand and capacity based on the regression analysis results or other uncertainty estimation approaches
Assessment of the Structural Health Monitoring of a Historic Reinforced Concrete Water Tower
No full textDegradation of Reinforced Concrete structures exposed to aggressive environment is of major concern in the construction industry. The work presented refers to the thorough assessment of a structure, the Water Tower at the Malta Civil Abattoir, exposed to an aggressive marine environment and its restoration using advanced materials, restoration technologies and monitoring systems. This Water Tower was constructed in the 1930s and is located in the Grand Harbour, close to the coast. It suffered severe degradation due to a coastal exposure. The restoration required a comprehensive approach covering different critical and important stages. The restoration of the structure and use as a Water Tank required an appreciation of the historic structure and relies also on the use of advanced materials which can address the requirements of the structure. The project included the following stages:
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Advanced appraisal of an industrial heritage structural for conservation, through materials testing, numerical structural modelling and scenario testing to optimise repair and strengthening interventions.
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Development and then the application of advanced ultra-high performance materials applied for the first time, including ultra-high performance self-healing nano-additive based concrete and carbon textile reinforced high performance concrete for the strengthening of the structure.
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Development of new techniques for restoration of concrete heritage structures including electro-chemical chloride extraction, re-alkalisation of reinforced concrete, epoxy injection and polymer concrete patch repair with corrosion inhibitors, re-integration of the structure, and an advanced sensor network system for monitoring over time.
New materials and technologies were developed to address the challenging conservation process. The innovative materials and technologies promote the long-term behaviour in the structure. These materials were developed for their use in the strengthening of the different elements in the structure; they consist primarily in the following high performance concrete systems:
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Ultra high performance – high durability fibre reinforced concrete with ultra-high strength self-healing and self-compacting propertied, applied to the columns
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Textile reinforced concrete with carbon textile / resin reinforcement with high strength and self-healing properties, applied to the tank.
The long-term monitoring approach is based on an advanced structural health and Durability monitoring system together with environmental monitoring. The system is based on 150 sensors embedded in the structure, the data collection and processing in real time, to monitor
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the long-term performance of the structure and also its performance during normal operation whilst in service for the storage of water. The advanced Sensor Network System included a Durability Monitoring system based on Galvanic, Resistivity and Embedded Reference Electrode sensors; Structural Health Monitoring based on strain gauges and accelerometers; Environmental Monitoring with a weather station which captures data on weather conditions including solar radiation, temperature and precipitation. The sensors are located in different structural elements and parts of the structure for overall monitoring. In addition, a microtremor ambient noise investigation was carried out before, during and after restoration, with monitoring of the tank also when empty and when full of water.
Data from the sensors related to monitoring is collected through the installation of a Data Acquisition System. Although the number of channels on this DAQ is limited, a number of multiplexers were used to expand this number of channels. Typically, these take readings once every few minutes for the durability and strain gauges, while continuous readings are taken for the accelerometers. The data gathered from the structural health and durability sensors is intended to understand the performance of the restored water tower over time with respect to different environmental conditions and actions during operation. The monitoring system was used during the validation process when the tank, having a capacity of 400 cubic m of water was filled in with water gradually and then emptied. The performance of the structure during a seismic event was also assessed with reference to the structural health monitoring sensor system. In addition, the performance of different sensors in different parts of the structure and different orientations was analysed.
The analysing of the data generated through the structural health monitoring system (strain gauges and accelerometers) indicated that the systems is capable of assessing the performance as anticipated at the design stage of the monitoring system. In addition, the sensor monitoring system indicated that the structure performs as per structural design considerations, when considering its behaviour at different stages, before and during filing in, with the tank full of water and on emptying the tank. The water tower’s performance over time is monitored through the durability sensor system intended to monitor degradation and assess the effectiveness of the restoration and the durability of the restoration and strengthening methods employed. The monitoring of the Reinforced Concrete Water Tower, allows for real time assessment of performance of the structure, supporting the conservation strategy
EVALUATION OF FRAGILITY OF INFILLED FRAME STRUCTURES SUBJECT AFTERSHOCKS BY MEANS OF DOUBLE INCREMENTAL DYNAMIC ANALYSIS APPROACH
No full textThe paper investigates the role of masonry infill walls on the seismic fragility of reinforced concrete structures
subject to mainshock/aftershock sequences. An assessment framework aimed at determining aftershock fragility
curves of bare frames and infilled frames is presented. The framework is based on a Double Incremental
Dynamic Analysis (D-IDA) approach, which provides the adoption of ground motions defined by combining a
fixed intensity mainshock with a set of variable intensity aftershocks. Mainshock (MS) intensity is scaled several
times and combined with the same set of aftershocks (AS). Chord-rotation and shear limit states are specifically
defined to consider the influence of masonry infills within frames. The OpenSees software platform is used to
carry out simulations by means of a fully fiber-section model of a reinforced concrete (RC) prototype structure.
Fragility curves and residual capacity diagrams obtained show that masonry infills can provide significant
additional capacity seismic to resist further shakings in comparison with bare frames, if reinforced concrete
members have sufficient shear resistance
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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