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Structural design of prestressed concrete continuous double tee beam bridges
No full textOne of the applications of prestressed concrete is in continuous bridges. These can be
either double tee or box girders. The longitudinal shape can be prismatic, semi-prismatic or non- prismatic. The design of these bridges otTer a considerable challenge to the design engineer due to the presence of secondary moments which are induced due to the prestressing forces. These introduce a considerable complexity to the design process. In this research, an attempt is made to develop a design method that would minimize the complexity associated with the design of prismatic prestressed concrete double tee bridges.
In concrete bridges, generally the minimization of self weight is important. This is used as the criterion to start the design process. The governing criteria for the various
components of the cross section is used to determine the smallest section that is practically possible. The methods to take account of short term and long term effects such as creep and shrinkage are also included for the cross section selected. Once the cross section is available, it is necessary to find appropriate cable forces. Design methods for both constant and variable cable forces are presented based on the line of thrust. It is shown that the use of variable cable forces could reduce the total cable forces thus leading to a saving in tendons.
For the selected cable forces, it is necessary to ensure that cable profile will be available within the selected section. The line of thrust can be transformed to fit within the section by selecting a suitable set of secondary moments. Thus, the secondary moment can be selected in a straightforward manner for both constant and variable cable forces.
Thus the cable profile selected should ensure that it fits within the limits of cable profile zone and also generate the selected secondary moments. This is not a trivial task. In order to simplify this task, a design method was introduced for both constant and variable cable forces. In the case of variable cable forces, there is a possibility to
have point moments and forces acting at the cable force change points. A method to deal with such forces is also introduced.
Therefore, it is possible to consider that this thesis presents a complete design method for the preliminary design of prismatic double tee prestressed concrete beam bridges either with constant or variable cable forces. It has also shown that it is possible to minimize the complexity of difficult design tasks by approaching the problem in modular fashion.
Keywords - Prestressed Concrete, Double Tee bridge
A design method for prismatic prestressed continuous box girder bridges
No full textPrestressed concrete is one of the most difficult building materials to design due to many reasons such as number of different solutions available for the same problem and the time dependent changes that take place. When used for continuous box girder bridges, there are added problems associated with secondary moments. In this paper, a straight forward design method has been presented that localises the iterations involved in the design process as much as possible so that the calculations involved can be minimised. The guidelines to determine the cross sectional dimensions has also been discussed. A complete design example has been presented for a three span continuous bridge. A simple method for modelling a box girder as a grillage of beams also has been presented
Design of continuous prismatic prestressed concrete spine beams with variable prestressing forces
No full textDesign of continuous prismatic prestressed concrete continuous spine beams is a complex task, primarily due to the secondary moments that occur as a result of the prestressing effects. In prestressed concrete members, it is useful to select the smallest possible section while satisfying the criteria like the use of a particular construction technique, constructability and stress limits. The methods that can be employed for selecting the smallest section dimensions by considering the global and local bending, constructability, restrictions on depth etc. are highlighted. It is advantageous to minimise the total cable force (∫Pds) used for a continuous prestressed concrete prismatic spine beam with respect to economy and constructability. It is shown in this paper that the total cable force cannot be minimised by using a constant cable force throughout the length. For that, different cable forces could be used in span and support regions. It is also shown that for any given section, there is a maximum cable force that should not be exceeded over the supports. The selection of secondary moments to ensure that the cable profile zone resulting from the minimum cable forces will lie within the section is also highlighted. When the cable force changes, there will be point moments and point forces that will act at those sections. A straight forward method is presented for dealing with these when finding the cable profile that will satisfy the stress limits and also generate the secondary moment distribution already selected at the beginning of the design
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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