1,720,962 research outputs found
Performance characterization of joints in S355 grade steel and quenched and tempered steels for structural applications
No full textAlthough in recent years the applicable regulations for the structural design of metal carpentry have been profoundly renewed, there is still a strong rootedness in concepts derived from centuries-old experience that very often limits the potential offered by the technological innovations of high-performance materials, as in the case of tempered steels. After verifying in the scientific literature, in the commercial literature of manufacturers and in the material databases, the availability of the main data necessary for the characterization of tempered steels usable in large metal carpentry, a wide experimental campaign was undertaken aimed at obtaining a characterization updated and specific mechanics for some types of materials, which allows the overcoming of the stringent requirements of current regulations on the use of these materials both for the base material and for the welded joints, homogeneous and heterogeneous. This work presents the main results obtained
A design approach to reduce hull weight of naval ships
No full textHull weight is a design parameter affecting the whole performances of a ship, being related to building costs, operational costs, maintenance and durability, and not least to satisfaction of functional requirements. Naval ships are no exception and impact of hull weight is crucial to fulfil mission requirements. In the light of the above, weight reduction is one of the main design drivers and it should be duly accounted for since the concept design phase. In this paper, a design approach intended for pre-contractual design phases is presented. It takes advantage of recent developments and trends of construction rules as well as of nowadays-available computation potential to update and improve the traditional scantling design approach, applied since decades by designers. The complexity and computational burden is kept to a minimum to provide a user-friendly procedure applicable in everyday working practice. Designers’ experience and judgment continue to drive the whole process. A Visual Basic support software has been developed with worksheet interfaces to implement the proposed scantling design procedure. Test cases showed significant weight reductions with respect to as-built ships and to scantling obtained by applying traditional design procedures
Ship weight reduction by parametric design of hull scantling
No full textIn this paper, a semi-automatic design procedure for concept and preliminary phases of hull structural design is
described. It allows investigating the design of ship structures, consisting of a series of stiffened panels surrounded
by primary members, assembled to form the hull girder. The optimal configuration of the structural layout
and the best scantling of each structural component (i.e. platings, ordinary stiffeners and primary elements)
is provided, accounting for interactions among all structural components as well as integration of primary,
secondary and tertiary responses. The proposed method allows the minimization of the overall weight of hull
blocks intended as the sum of stiffened panels’ weight (shell and stiffeners) plus that of the surrounding primary
members. A dedicated application in VBA language (Visual Basic for Applications) has been developed in which
scantling checks have been implemented by applying a few rules formulations after a comprehensive analysis of
involved variables defining the state of the hull structural system. The proposed scantling design approach is very
practical, it follows well-known hull structural design principles and it takes advantage of the nowadays widely
available computation means to update the traditional sequence of the scantling checks in a more rational way
and to select the optimal lay-out scantling solutions among truly feasible ones
Caratterizzazione delle prestazioni di giunti in acciaio grado S355 e acciai bonificati per applicazioni strutturali
No full textNonostante negli ultimi anni le normative applicabili per la progettazione strutturale della carpenteria metallica siano state profondamente rinnovate, permane tuttavia un forte radicamento a concetti derivati da un’esperienza secolare che limita molto spesso le potenzialità offerte dalle innovazioni tecnologiche dei materiali ad alte prestazioni, come nel caso degli acciai bonificati.
Dopo aver verificato in letteratura scientifica, in quella commerciale dei produttori e nei database dei materiali la disponibilità dei principali dati necessari per la caratterizzazione di acciai bonificati utilizzabili nella carpenteria metallica di grandi dimensioni, è stata intrapresa un’ampia campagna sperimentale finalizzata ad ottenere una caratterizzazione meccanica aggiornata e specifica per alcune tipologie di materiali, che consenta il superamento delle stringenti prescrizioni delle attuali normative vigenti sull’utilizzo di questi materiali sia per il materiale base sia per le giunzioni saldate, omogenee ed eterogenee.
Questo lavoro presenta i principali risultati ottenuti
Analysis of the dimensions of the lightening holes in the deck beams of a hull
No full textThe proposed work describes a procedure for sizing primary structural elements in the initial phase of ship design, with the aim of determining the maximum dimensions of the lightening holes usually found in the webs of beams, which are also necessary for the passage of plant components. The objective is to simplify the process for a more effective and integrated result from the earliest stages of design. In particular, the dimensioning of a ship's hull, although a complex problem, is often governed by a few independent variables with often limited ranges of variation. The optimal choice is therefore obtained by systematically analyzing and comparing the solutions that are actually feasible in practice. The systematic analysis will provide designers with rational data for choosing the dimensions of the beams, with a view to finding the best solution in terms of weight-strength and maximum size of the lightening holes. The study combines analytical and numerical methods with design experience, integrating the results into the design process using a VBA code
A rational approach for the scantling design of GRP pleasure crafts
No full textIn various fields of industrial engineering, including naval architecture, structural design is considered one of the most challenging steps by designers as it shall accommodate all other design aspects, likely already defined in earlier steps. Moreover, structures need to comply with specific requirements, i.e. limit states, while also performing in accordance with user's demands in terms of mission profile. In a goal-based design perspective, limit state criteria have to be defined accounting for both, structural robustness, functional and operational demands. Construction feasibility is an issue as well, further constraining the scantling design. Balancing construction needs, ship performances and structural aspects is not always an easy task.
The environment in which a ship operates is indeed complex and verification of safety and robustness is usually carried out in accordance with classification societies and other rules, possibly applying direct calculations whenever applicable rules do not provide suitable solutions. At the same time, the asset needs to fulfill various attributes specified by the owner. As a matter of facts, the scantling design is mathematically a multivariate and over-constrained problem whose feasible solutions are in fact rather few. In the case of composite pleasure craft hull structures, while the number of design variables increases, feasibility constraints also largely reduce the design space.
To address these challenges, designers may nowadays exploit new procedures able to reduce structural weight, though ensuring that the asset performs safely and adequately meeting client's requirements. To achieve this, designers may combine a more rational design philosophy with currently available numerical problem-solving applications to obtain a rational trade-off among all actually feasible solutions, which are relatively few.
Thus, the objective of this study is to present a dependable numerical method for determining the scantling while reducing the weight of hull composite structures of pleasure crafts. This method aims to provide the most suitable, high-performing, and safe layout in the quickest and easiest possible manner. It turns out that counterintuitive, yet feasible and fit-for-purpose, structural lay-outs can be obtained
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
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