VSH Turòa nad Bodvou - Nemetschek Scia

Introduction
The aim of this project was to prove that the internal structure of a
luxury yacht would be strong enough to support the cradle forces
exerted on the yacht as it was transported out of the production
hall and onto the ship lift.
The main concern in this case was that usually the cradles are placed
directly under the transverse bulkheads of the vessel; in this case
however the forward cradles would have to be placed between
the bulkheads to facilitate access to the ship lift. This resulted in a
large force being introduced into the vessel on a very local scale if
compared to the normal situation of the vessel in water.
Method of analysis
This project determined the resulting stresses in the vessel due to
the cradle being positioned between the bulkheads 65 and 80.
The calculation covers all stresses occurring in the structure due to
the introduced cradle load. The fore part of the ship was built up of
mainly plates without additional stiffening. The reason for this was
if could be shown that the main plate fields without the additional
stiffening could support the introduced load. It can be concluded
that the stiffened structure will meet the requirements. This results
in the shell being modelled excluding the stiffeners. This approach
has been chosen in order to ensure that the stress levels remain
within the allowable limits.
SCIA•ESA PT allows the modelling of accurate models of curved
plates. They are created in order to determine deformations and
internal stresses. This delivers accurate results since the interaction
between the various plating and beams is taken into
consideration.
The modelled section of the vessel, from frames 65 to 80, was
supported by fixed line supports along the entire edge of the bulkheads.
Thus basically the section was pinned between the bulkheads
and then forced to bend under the introduced load. This is
a very conservative approach since the section is not actually fixed
between the bulkheads. However this approach was taken to
ensure that the calculated stresses would also be on the conservative
side.
Only one side, namely the starboard side, of the forward section
was modelled. Since the vessel is symmetrical, it was sufficient to
model only one side.
Rules and Regulations
The following rules and regulations were used to complete the
check of the internal structures of the vessel:
• Lloyd’s Register Rules and Regulations
• Rules and Regulations for the Classification of Special Service
Craft, July 2003, incorporating Notices No. 1 and 2
• Part 6 Hull Construction in Steel
Yacht on transport cradles - Analyisis of internal structure
Loads
The load exerted onto the vessel was determined by using the
maximum capacity of the Mammoet load liners used to transport
the vessel. These load liners would be lifting the large cradles on
which the entire weight of the vessel would be resting.
Basically the entire vessel would be supported on 4 cradles, with
2 supports points each, one on the port side and one on the starboard
side. Between the steel of the cradle and the steel hull, a
layer of wood was used to attempt to reduce the “hard point” of
the load.
A load of 176 tons had to be introduced into the vessel between
frames 65 and 80. The support area was 3,0m by 1,8m, resulting in
a surface area of roughly 290kN/m2 .
Results
The results proved that the vessel would be able to support the
introduced cradle loads between the bulkheads without any modifications
to the vessel. The conservative approach ensured that the
actual deflections and stresses that occurred during the transport
did not have any adverse effect on the yacht.
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