1,721,151 research outputs found
Combination of Stochastic Loads for a Reliability Evaluation of the Hull Girder in Extreme Conditions
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Comparison among simplified procedures for fatigue assessment recommended by classification societies rules
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Experimental modal analysis of a ship deck structure
No full textThe work focuses on a deck panel of a fast ferry and is aimed at
characterising its vibrational behaviour in terms of modal shapes and
frequencies.
Surveys are performed on a full scale physical model of about 3 x 2.5 m
tested in the DINAV structural lab.
Accelerations in the direction normal to the deck plate surface are
measured and frequency response functions are derived between the survey
locations and the position where an impulsive excitation is applied. Records are
post-processed in order to get modal characteristics (shape, frequency and
damping inherent to each mode). The work is propaedeutic to an investigation
on the influence of typical structural modifications (insertion of a reinforced
beams, change in stiffeners spacing) on the vibrational behaviour. The long
term target is to control noise transmission into the living areas placed above
the deck by intervention on the modal characteristics of the panel
Characterisation of noise counter-measures for cabin floors
No full textA growing attention has been devoted to acoustical problems on board of ships, particularly in
connection with the recent, extensive production of high standard cruise vessels.
Severe specifications on the maximum noise levels in the various areas of the ship and in
particular in the living and working areas are now common.
This brought the need, since the first steps of the design, for a careful acoustical planning,
based on a detailed analysis of the various elements of the “acoustic circuit”. This approach
implies in general to consider sources on board (power and location), transmission paths and
receiving positions.
The work concentrates on the final part of the transmission path and regards the anti-noise
measures that are utilised for the cabin walls (particularly on the floor) to reduce the noise
radiated inside the room.
Such measures have been applied since a long time by the shipyards, but mostly with
empirical methods, based on a trial-and-error procedure.
The aim of the present work is to summarise the physical concepts that are at the bases of the
noise counter-measures and to review the physical quantities that can be used to quantify their
effectiveness.
The case of the application of viscoelastic materials in a constrained layer arrangement to the
cabin floor is discussed in particular, with a description of the main material and geometrical
parameters and an evaluation of their influence on the performance of the treatment.
A description is included of a simplified procedure for a comparative testing of different
viscoelastic materials and of some results of this procedure
Reliability analysis of the primary strength of an oil tanker
No full textA procedure is presented to perform a second order reliability-based structural analysis of the mid ship
section of a vessel. The procedure accounts for the combination of the vertical and horizontal components of
the wave induced bending moment as well as of the still water bending moment, in order to determine the
actual angle gamma formed with the vertical plane by the total resultant bending moment.
The ultimate strength of the midship section is considered as a function of the same angle.
The proposed analysis is applied to a double hull tanker on a particular route (Persic Gulf - North Europe
and ballast return trip) and directional scatter diagrams are used for the description of the sea states
encountered during the voyage.
The results are compared to those obtained on the same test case with a simpler model, which takes into
account only the vertical components of loads and strength. The comparison shows that the introduction in
the load model of the horizontal component of the bending moment does not reduce the structural reliability
of the considered oil tanker ship. Such result is to be related to the shape of the curve of hull girder ultimate
strength as a function of gamma, which shows a local minimum for pure vertical bending moment: in the examined
case, the most dangerous condition is obtained in such situation
Vibrational Behaviour of a Deck Panel of a Fast Ferry
No full textThe present report deals with the characterisation of a ship structural panel in terms of vibrational behaviour.
An experimental modal analysis was carried out on a full scale model of deck panel of a fast ferry-boat. Results are
compared with a numerical analysis carried out by means of a FEM procedure and with simplified analytical models.
The comparison is performed in terms of resonance frequencies and of corresponding modal shapes.
An analysis of results of both investigation allows an interpretation of the dynamics of the panel in terms of an assembly of
elementary subpanels bounded by primary and ordinary stiffeners. The long term aim of the study is to investigate noise
radiation into the living spaces located on the deck
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