1,721,011 research outputs found
FE modelling and updating of unique fink truss footbridge
No full textRecent improvement of mechanical characteristics of structural materials and fast development of the
finite element (FE) based computational structural analysis are resulting in innovative solutions in
footbridge design. When doing research into dynamic analysis of these structures, their dynamic
properties are required and are usually obtained from an FE model. However, because of structural
complexity, the FE modelling of footbridges is often prone to errors due to modelling uncertainty. The
best and quite often the only way to evaluate the reliability of the FE modelling is to involve modal testing
and FE model updating of footbridge structure with the aim to match test results. Using this approach, a
complex and rather unique Fink truss structure of Royal Victoria Dock Bridge in London was analysed.
Eleven measured modes of vibration were identified via an ambient vibration survey and then compared
with their counterparts from an initial FE model developed by best engineering judgment. In this initial FE
model the maximum difference between two paired natural frequencies was 29%. In a subsequent
updating exercise it was found that uncertainties in main beam and crosshead geometry, as well as the
inherent simplicity of the fully symmetric FE model, were the main source of the modelling error
Vibration performance of a lightweight FRP footbridge under human dynamic excitation
No full textFibre-reinforced polymer (FRP) composites are increasingly used as main load bearing materials in design of pedestrian bridges. The FRP footbridges are typically characterised by high strength, and relatively low mass and stiffness. These properties could lead to excessive vibration response under human-induced dynamic loading. This paper studies dynamic performance of a 19.8 m long, simply supported, FRP footbridge exposed to walking and jogging. Moreover, the vibration response of this bridge is compared and critically evaluated against the response of an equivalent, in terms of natural frequency and span length, composite steel-concrete structure. The main factors that drive the vibration performance of the FRP structure are discussed and some recommendations for vibration serviceability checks are made
Effect of group walking traffic on dynamic properties of pedestrian structures
Full text linkThe increasing number of reported vibration serviceability problems in newly built pedestrian structures, such as footbridges and floors, under walking load has attracted considerable attention in the civil engineering community over the past two decades. The key design challenges are: the inter- and intra-subject variability of walking people, the unknown mechanisms of their interaction with the vibrating walking surfaces and the synchronisation between individuals in a group. Ignoring all or some of these factors makes the current design methods an inconsistent approximation of reality. This often leads to considerable over- or under-estimation of the structural response, yielding an unreliable assessment of vibration performance
Statistical characterisation of parameters defining human walking as observed on an indoor passerelle
No full textIncreased slenderness of footbridge structures in the last few decades has led to an
increasing number of vibration serviceability problems under human induced dynamic load,
such as walking. These problems are typically related to increased discomfort of footbridge users
due to perceptible vibrations during footbridge crossing. The current codes of practice dealing
with the vibration serviceability of footbridges often fail to assess reliably the vibration level
induced by humans. This is because they model the load induced by pedestrians by considering
only an ‘average’ walker. However, because of natural diversity in human population, so called
inter-subject variability, it is necessary to model the walking force in a probabilistic way taking
into account this type of variability. To do this, a large database of parameters (such as walking
frequency, step length and weight) describing walking force induced by different individuals is
required. Currently, only limited amount of data to populate this database is available. To generate
more data of this kind, pedestrian traffic on an indoor passerelle inside a University campus
in Sheffield was monitored using video cameras for 6.5 hours. The data that characterise
human walking (such as walking frequency, step length and arrival time) were collected and
analysed statistically. Based on this, the probability density functions for the parameters analysed
were constructed. The results of this study could be used when defining a badly needed
probabilistic force models for vibration serviceability assessment of indoor passerelles of this
kind
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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