1,720,962 research outputs found
Prediction of degree of bending in tubular X and DT joints
No full textAnalysis of the large scale fatigue testing results of offshore welded tubular joints showed that the fatigue life is not dependent on the hot spot stress alone, but is also significantly influenced by the through thickness stress distribution which can be characterised by degree of bending (DoB). Accurate prediction of DoB data in tubular joints is crucial for improving the accuracy of fatigue life prediction using stress-life (S-N) curve and particularly for predicting fatigue crack growth using the fracture mechanics method. However, there is no set of DoB parametric equations available for tubular X and DT joints. For this reason, comprehensive thin shell finite element (FE) analyses were carried out for 330 tubular X and DT joints typical of those used in offshore structures, under six different modes of loading. The results of these FE analyses were used to derive a set of parametric equations to predict the DoBs at the critical positions on both brace and chord toes in tubular X and DT-joints under each mode of loading. • 1999 Elsevier Science Ltd. All rights reserved
Prediction of stress distributions along the intersection of tubular Y and T-joints
No full textSeveral sets of stress parametric equations have been derived for fatigue strength assessment of tubular Y and T-joints. Among them, the Hellier, Connolly and Dover (HCD) set is the only one which can provide the whole two dimensional (2D) stress information. However, the HCD characteristic stress distribution equations were derived from the limited number of typical finite element (FE) results and thus may not be able to capture the effects of all joint geometric parameters. As part of a large study including X and DT-joints, comprehensive thin shell FE analyses were carried out for 330 different tubular Y and T-joints and the whole FE result database was used to derive a new set of equations as a function of joint geometric parameters. These equations can be used to predict stress distributions along the intersection and also provide an alternative method for the calculation of the hot spot stress concentration factor (SCF). Furthermore, an improved methodology has been suggested for assessment of stress parametric equations
Parametric equations to predict stress distributions along the intersection of tubular X and DT-joints
No full textAccurate information on stress distributions along the intersection is required for fatigue strength assessment of tubular joints. However, there is no parametric equation currently available in the open literature to predict this information for tubular X and DT-joints. Systematic thin shell finite element (FE) analyses have been conducted for 330 different tubular X and DT-joints, typical of those used in offshore structures, subjected to six different modes of loading. A novel two dimensional regression methodology was developed to curve-fit all of the FE results from this work. A set of parametric equations was derived to predict the stress distributions along both chord and brace toes in tubular X and DT-joints under each mode of loading. These equations were assessed by comparing the predictions with available experimental data. Validation results show that they can be used to predict stress concentration factor (SCF) distributions along the intersection but also provide an alternative method for calculation of hot spot SCF
Stress concentration factor parametric equations for tubular X and DT joints
No full textDuring the design stage, the peak stress is usually needed for estimating the fatigue life of offshore tubular welded joints by an S-N approach. However, for fracture mechanics calculations of remaining life, on cracked joints in service, information is required on the magnitude and distribution of the stress acting in the anticipated crack path, not just the peak stress at one location. Fatigue crack propagation rates are important to reliability-based inspection scheduling: hence the need for this information is becoming more pressing. Parametric equations are available for Y and T joints in terms of peak stress, stress distribution and bending-to-membrane ratio. However, for X and DT joints, there are no parametric equations for stress variation through the thickness and around the intersection. Even for stress concentration factor (SCF), so far there is no full set of parametric equations especially for single-brace loading. Thin-shell finite element analyses have been conducted for 330 X and DT joints typical of those used in offshore structures, subject to six modes of loading. The results from this work have been used to produce a new set of parametric equations as a function of non-dimensional joint geometric ratios α, β, γ, τ and θ by carrying out regression analysis. These equations can be used to predict SCFs at the crown toe, saddle, crown heel and hot-spot positions for each mode of loading, for both chord and brace, as well as the angular location of the hot-spot stress site around the intersection. This set of SCF parametric equations has been assessed by comparing the predicted values with results from steel and acrylic model tests and also with the predictions from existing parametric formulae given in the literature. The degree of bending data, and stress distribution data, will be reported in other publications
Decommissioning of large offshore structures – The role of an Independent Review Group (IRG)
No full textMost proposals for the construction or decommissioning of large offshore structures will need to address a range of issues including the use of innovative technologies, environmental impact, health and safety risks, regulatory requirements and public acceptability. Usually, several options will be examined and run through a Comparative Assessment before a final selection. There is also the need to keep stakeholders informed as the project proposals develop. Many of the issues require complex scientific or engineering studies and risk assessments frequently outsourced to contractors. The information in their reports feeds the Comparative Assessment. However, it may be difficult for stakeholders, or even the regulating agency, to judge the veracity of such technically complex issues and feel confident that the evidence for the final project proposal is soundly based. Failure to adequately exchange information has led to open confrontation in the past. An approach which can provide greater transparency and confidence in the outcome is to set up a review group of independent professionals with wide expertise at the outset of a project. This paper discusses the benefits of an Independent Review Group (IRG) to the Commissioning Organisation, regulating authorities, the industrial sector and stakeholder public interests, and describes the experience of the authors with such a body
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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