1,004 research outputs found
Parametric Evaluation of the Effective Breadth for GRP Beams with FEM Calculation
No full textThe direct scantling of reinforced plates can be performed by simplified grillage theory or
by FEM codes. The first approach gives satisfactory results and better matches
Classification Society Rules. The only problem is represented by the determination of
beam geometry which implies the determination of the shell portion cooperating with the
reinforcement. The width of this strip, called “Effective Breadth Be”, depends on several
geometric characteristics like the shell thickness t, the beam span L, the beam distance B
and the dimensions of the beam transverse section. In the case of steel plates the
relationships between the above parameters and Be is well known and several procedures
are available in literature and provided by the Classification Societies rules for determining
the effective breadth.
More uncertainties exists for what GRP structures are concerned. In this case the only
references are represented by semi empirical Classification Societies formulas which give
Be just as a function of the shell thickness. For this reason, and in cooperation with the
Italian Classification Society, an investigation on this matter has been started by the author
considering both single skin and sandwich shells. The analysis has been performed by
FEM calculations on a number of numerical models each of them obtained by a different
combination of the values of the considered parameters that are: the shell thickness t, the
L/B ratio and the transverse section dimensions of the beam.
The results have been presented on diagrams with Be/B ratio versus L/B ratio with different
combination of the evaluated parameters. A comparison of the curves with the values
provided by Classification Societies has been performed as well. Finally all the results
have been utilised to obtain a regression curve by which it is possible to evaluate the
Effective Breadth by considering all the considered geometric characteristics
A method to assess the seakeeping behaviour of a merchant ship in its early stage of design
No full textIn the early stage of ship design a first choice of the main dimensions can be
performed utilizing several methodologies available in literature. A further
optimization process is then necessary and, in doing so, useful tools are
furnished by standard series and data bases for the prediction of performances
in calm sea. Such a philosophy may also be applied to seakeeping responses in
order to predict the behaviour and the relative merit of a series of
different design solutions all verifying the same contractual requirements and
constraints.
In this paper a procedure is presented to compare different ship designs in
their early stage from the seakeeping point of view. The first phase of the
proposed procedure consists in the computation of the seakeeping quantities of
interest, utilizing a matrix of seakeeping data calculated for a standard series
of merchant ships. In the second phase the responses are weighted on the base of
the environment in which the ship will operate and a merit index, similar to that
proposed by Bales, is determined. As an illustrative example, the procedure has
been applied to four different classes of Ro-Ro ships.
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