170,339 research outputs found
Verifica del dimensionamento della sezione maestra di yacht da 55’ con i regolamenti RINA, ISO, DNV e ABS (nuova valutazione delle caratteristiche meccaniche – nuovi spessori laminati)
No full textRapporto interno contratto DINAV-AZIMU
Evaluation of Classification Societies Rules for GRP Motor Yachts
No full textIn this paper the scantling procedures contained in the “Design and Construction of Pleasure Boats” Rules of the Italian Classification Society RINA, relatively to GRP vessels, are assessed in detail. This work represents the continuation of a joint research performed in cooperation by AZIMUT Shipyards in Avigliana (Italy) and the Dipartimento di Ingegneria Navale of the University of Genova.
Scantling procedures contained in Classification Societies Rules are based mainly on minimum requirement formulas, corrected by semi-empirical coefficients and safety factors, which take into account possible uncertainties about material behavior, stiffener sections and geometric imperfections.
In order to check the efficiency of these safety factors, a specific study has been started up within the joint research.
In the first phase of the investigation a statistical analysis of dimensional and geometric characteristics of a number of medium size motor yachts have been performed, aiming at expressing the main scantling formulas as a function of minimum number of variables.
In the second phase several versions of the same part of a 55’ motor yacht, chosen as reference vessel, have been obtained by parametrically varying the main scantling variables
In the third phase, for each of the obtained structures, the correspondent finite element model has been created by the FEM code NASTRAN. Finally the safety factors of RINA scantling formulas have been evaluated by studying the stress levels of all models and comparing them with the RINA equivalent stress level
Pesata delle Sezioni Maestre di yacht da 55’ realizzate con le Schede di Laminazione derivanti dai Regolamenti RINA – ISO – DNV
No full textRapporto interno contratto DINAV-AZIMU
Verifica del dimensionamento della sezione maestra di uno yacht da 55’ con i regolamenti RINA, ISO, DNV e ABS
No full textRapporto Interno contratto DINAV-AZIMU
Analisi delle normative sulle unità da diporto in vetroresina con metodi numerici e sperimentali
No full textIn this paper the scantling procedures contained in the “Rules for the Construction and Classification of Pleasure Vessels” of the Italian Classification Society RINA, relatively to GRP vessels, are assessed in detail. This work represents the continuation of a joint research performed in cooperation by AZIMUT Shipyards in Avigliana (Italy) and the Dipartimento di Ingegneria Navale of the University of Genova. In the first phase of the investigation a statistical analysis of dimensional and geometric characteristics of a number of medium size motor yachts have been performed, aiming at expressing the main scantling formulas as a function of minimum number of variables. In the second phase several versions of the same part of a 55’ motor yacht, chosen as reference vessel, have been obtained by parametrically varying the main scantling variables: for each of them the correspondent finite element model has been created by the FEM code NASTRAN. Finally the safety factors of RINA scantling formulas have been evaluated by studying the stress levels of all models and comparing them with the RINA equivalent stress level
On "Literature Reviews of, and for, Educational Research": A Response to the Critique by Joseph Maxwell
No full textWe thank Joseph Maxwell (this issue of Educational Researcher, pp. 28–31) for accepting our invitation to examine the roles and expectations of dissertation literature reviews. We agree that most are inadequate but disagree why. Maxwell argues that dissertations should emulate research articles and include a conceptual framework that only discusses relevant literature. Candidates need not present a thorough analysis and synthesis of the scholarship and research, Maxwell argues, or justify claims made about the literature. Finally, he asserts that we misunderstand the relationship between literature and research, leading to an accusation of “foundationalism.” However, these specific disagreements ignore fundamental differences about the purposes of the doctoral dissertation and the relationship between those purposes and doctoral program goals. In this rejoinder, we briefly explore these conceptual and normative differences
Parametric investigation on stress concentrations of bulk carrier hatch corners
No full textOwing to the hull structure complexity and severe load conditions, bulk carrier ships are the subject of an in-tense research activity by Classification Societies and research centres. Many problems affecting this kind of vessel derive from loading and unloading operations, corrosion and fatigue phenomena and, sometimes, the age of the ship.
For what the structural strength is concerned, one of the typical failure causes for bulk carriers is represented by high stress concentrations occurring in deck plating close to hatch corners in way of coaming stay.
The aim of this work, performed in cooperation by the Registro Italiano Navale (RINA) and the Department of Naval Architecture and Ship Construction of the University of Genova, is to investigate the stress distribu-tion close to hatch corners in a systematic way, in order to determine and quantify the influence of the select-ed parameters on this phenomeno
Structural design of a medium size passenger vessel with low wake wash
No full textThe main features are presented related to the development of an innovative passenger ship, starting from the concept design up to the final realization of the real scale prototype. The vessel herein enlightened is represented by a very unconventional solution for the employment in the short range passenger traffic with a low environmental impact. The proposed solution has been inspired by both hydrofoil and SWATH technol-ogies with the aim of matching relatively high transfer speeds, low environmental impact and reduced wave washing phenomena.
The Department of Naval Architecture of the University of Genova cooperated with Rodriquez Cantieri Navali to develop the complete design of this new vessel. In this paper the structural design is described, starting from a first, preliminary approach by HSC Rules. Preliminary studies, on simplified numerical models, have also been performed to evaluate the mutual interaction between the hull and the submerged structure.
The main information have been collected in order to setup a finite element model suitable to simulate the behaviour of the structure as a whole. Starting from this model subsequent implementations have been car-ried out improving the investigation of stress and strain distributions
Stress Analysis of Bulk Carrier Hatch Corners
No full textOne of the most frequent damage cause for bulk carrier ships is represented by high stress
concentrations occurring in deck plating close to hatch corners in way of coaming stay. In this
area many fractures are found during surveys which are generated mainly by three types of
problems:
• stress concentration in correspondence of deck large openings;
• bad design of stays;
• different thickness between transversal and external deck plates.
The typical approach followed by IACS classification societies consists in a wide range of
qualitative suggestion (transversal stiffening for transversal deck strip, elliptical hatch corner
etc.) and a very simple formula providing the extra thickness of the hatch corner compulsory
insert.
This solution seems to be inadequate to face this phenomenon and a better knowledge is
mandatory to understand which parameters are more influent on stress distribution and
concentration.
The purpose of the analysis herein presented is to identify most important parameters and to
study their influence, in order to develop a more sophisticate procedure to be used in
preliminary design stage.
The investigation has been developed starting from the analysis of five different bulk carriers,
selected on the basis of their geometric and structural properties, and modeled with FEM
software Leonardo hull 3D v. 2.4.1.
The analysis has been divided into two sub-problems:
• study of b/B ratio influence (hatch breadth versus ship breadth);
• study of lw/b ratio influence (cross deck length versus hatch breadt)..
Two different series of FEM models have been realized:
Global models of the hull extended to a portion of three cargo holds;
Simplified models with increasing refinement degree.
All global models have a relatively coarse mesh and are loaded with a wide number of
loading condition (homogeneous, heavy and light ballast, alternate ore) corresponding to
relevant RINA load cases in order to maximize the effects. For what simplified models are concerned four different types of models have been analysed:
a) The first model consists in a simple plate with a rectangular opening and two longitudinal
box structures simulating the wing tanks. All the parts of the model have a constant thickness.
b) A second series of models has then been created, similar to the first one, adding a coaming
around the hatch opening. As in the first case the thickness has been maintained constant.
c) The third series is similar to the first one but the thicknesses of the lateral deck strip and of
the cross deck have different values, according to the real case.
d) The fourth series is similar to the second one. Again deck plates have different thicknesses. For all the models the results have been processed to calculate stress concentration factors “k”
(defined as longitudinal stress close to hatch corner versus theoretical hull girder stress) for all
selected loading conditions.
From the “k” coefficients obtained for every model, a “stress concentration surface”, as a
function of b/B and w/b, has been drawn and expressed by a simplified formula
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