One of the drivers for our software development
process is to keep pace with the ever changing portfolio of design
rules applicable to the wide range of vessels that are designed using
Maxsurf each year.
In the version 15 release our focus has been
on the new probabilistic methods for assessing damage stability. To
this end we have added a new version of Hydromax to our Maxsurf suite.
Hydromax Ultimate is the most capable version of that module and
includes all of the capabilities of Hydromax Pro, plus the new
probabilistic damage stability functions. Hydromax Ultimate is
available for purchase by existing Hydromax owners by paying the
difference in price between the two versions.
As well as
adding Hydromax Ultimate, we have also upgraded many of the Maxsurf
modules with new capabilities. The details of those changes follow
below. All members of the Maxsurf subscription program will be sent
Maxsurf version 15 over the coming weeks. Contact your local
distributor or FormSys directly for a price quotation to add Hydromax
Ultimate to your suite of software.
|Single and multiple zones of damage (Enlarge)|
Probabilistic Damage Stability
Hydromax Ultimate supports checking probabilistic damage requirements
as defined in IMO Resolution MSC.216(82) as well as the older
formulation of MSC.19(58). MSC.216(82) applies to all cargo ships of
80m or more in length and to all passenger ships regardless of length,
built from 1 January 2009 onwards.
The International Maritime Organisation (IMO) summarises the probabilistic approach to damage stability as follows:
probabilistic concept was originally developed in 1973 through study of
data relating to collisions collected by IMO and adopted by resolution
A.265 (VIII). This showed a pattern in accidents which could be used in
improving the design of ships.
Most damage, for example, is
sustained in the forward part of ships and it seemed logical,
therefore, to improve the standard of subdivision there rather than
towards the stern. The probabilistic concept is based on statistical
evidence concerning what actually happens when ships collide, in terms
of sea state and weather conditions; extent and location of damage;
speed and course of ship; and whether the ship survived or sank.
the probabilistic concept is believed to be far more realistic than the
earlier “deterministic” method, in which ships’ subdivision is based on
The probabilistic concept was
introduced into SOLAS regulations for passenger ships in 1978 in the
1978 SOLAS Protocol. The probabilistic concept was introduced into
SOLAS for cargo ships in 1990, applicable to cargo ships of 100 metres
or more in length built on or after 1 February 1992; and in 1996 to
cargo ships between 80 metres and 100 metres.”
The fundamental approach of the probabilistic damage analysis is to
first assume that the vessel has been damaged, then to assign a
probability (p) that the damage will occur in a certain area of the
ship. Given that the damage has occurred, a probability that the vessel
will survive (s) is then calculated from certain parameters of the GZ
curve calculated for the vessel in that damage condition. The
conditional probability that the vessel will sustain certain damage and
survive is then given by the product p.s; by summing this probability
for a range of different damage scenarios, the total probability of the
vessel surviving a damage incident is calculated – this is the attained
index (A). The attained index can then be compared with a required
index (R) to determine if the vessel is sufficiently safe.
Probabilistic damage workflow in Hydromax
It is useful to illustrate how it is envisaged that a user would use Hydromax to perform a probabilistic damage analysis:
1. The vessel is modelled in Maxsurf and tank and compartment definition is performed in Hydromax as usual.
The user defines other ship data required for the probabilistic damage
analysis. This data includes the vessel type, which load cases to
consider, and the number of adjacent damage zones to consider.
3. The user defines the boundaries of the damage zones
4. Longitudinal bulkhead and deck locations are defined for each zone and groups of adjacent zones.
Once steps 2 and 3 have been completed, the p-factors are automatically
calculated and displayed as the zone data is modified. With the
bulkheads and decks defined in step 4, the r- and v-factors are also
6. When the zones have been defined the user can then
define which tanks are damaged in each zone and sub-zone. A first pass
at this can be automatically generated using the Extent of Damage
command which automatically detects which compartments would be
breached by the corresponding damage (sub) zone.
7. The user can
then perform a probabilistic damage analysis. Hydromax runs a large
angle stability analysis for each combination of loadcase and damage
and collates the results to calculate the attained index. This index
(A) is then compared with the required index R to determine a pass or
|Logitudinal, transverse and vertical zone definitions (Enlarge)|
Main parameters, subdivision and calculation of required subdivision index
Hydromax Ultimate is able to perform probabilistic damage analysis
according to MSC.216(82) and MSC.19(58). Several new sheets have been
added to the Damage window where the user can specify the relevant
parameters required for the analysis. This includes: global hull
parameters; loadcases that define the different loading conditions;
longitudinal, transverse and vertical subdivision to be used; etc. Once
these main parameters have been specified, the required index and
probability factors (p, r and v) are automatically calculated. At this
stage the user can decide whether further subdivision might be
appropriate: a finer subdivision will potentially increase the attained
index but at the cost of longer analysis time.
|Attained index vs number of damage conditions (Enlarge)|
Zone and Sub-Zone Damage Specification
The damage for each zone and sub-zone is defined in a similar way to
damage cases - that is by the selection of tanks and compartments. This
defines which tanks and compartments are damaged for each zone or sub
zone; from this Hydromax can work out the damage for each of the damage
cases to be computed. The damage can be automatically generated and/or
in the Probabilistic Damage analysis mode the damaged compartments for
the currently selected zone or sub-zone are displayed in the design
view. Again this facilitates verification of the input data.
|Zones graphically highlight when selected (Enlarge)|
The calculation of the s-factors is done from the GZ curve calculated
for each combination of loadcase and damage condition. The parameters
for the GZ curve analysis may be set up in the same way as for a Large
Angle Stability analysis and the parameters for calculation of the
s-factors are defined in stability criteria (these same criteria are
also available in Large Angle Stability analysis mode should manual
verification of any of the individual Probabilistic Damage conditions
Once all the parameters have been specified, the analysis may then be
run. Large angle stability analyses are computed for each combination
of loadcase and zone damage up to either the specified maximum number
of adjacent zones or minimum specified p-factor. As this analysis can
be time consuming, Hydromax Ultimate adds support for calculations on
multi-core processors. This can speed up analysis on a quad-core
machine by 50%.
completion, basic data pertinent to calculation of the s-factor is
presented as well as a total attained subdivision index at the bottom
of the table.
The library of stability critieria in Hydromax continues to grow. The
latest addition is IMO resolution MSC.267(85) “Adoption of the
international code on intact stability”.
Simplifying Design Management
As our Maxsurf users use more surfaces, more trimming and larger
numbers of tanks and compartments, managing the objects in the design
becomes more of an issue. Two new capabilities help with this process.
In Maxsurf, a new command to automatically show all of the surfaces
which intersect the selected surface is very useful when managing
Hydromax, the extension of the assembly tree to this program helps both
with the management of surface visibility and also with managing tanks
In addition Hydromax adds a new property
sheet for tanks and compartments. This sheet is similar to the property
sheet for control points and markers in Maxsurf and allows quick
modification of tank properties from a graphical selection.
|Automatically showing all intersecting surfaces (Enlarge)|
|New assembly tree, tank selection & tank property sheets (Enlarge)|
|Blount & Fox style fishing boat hull (Enlarge)|
Hullspeed - Blount & Fox for Planing Craft
A new resistance prediction method based on the paper “Small–Craft
Power Prediction” by Donald Blount and David Fox has been included into
Hullspeed. This method is used for estimating the resistance of planing
hulls when in the planing speed regime. The algorithm is based on the
Savitsky planing method with improvements to the algorithm at “hump
speed” - the speed at which the vessel just begins to plane. The
method is considered superior to the Savitsky planning method (which is
based on prismatic hullforms) for vessels with variable deadrise and/or
beam in the afterbody.
|Suezmax tanker similar to that being built by EAS (Enlarge)|
Project Profile - EAS Brazil
After many decades of up and down economic growth, Brazil is emerging
as a real powerhouse in the world economy. Much of the current growth
is being driven by a massive expansion in offshore oil exploration and
production. Estaleiro Atlântico Sul (EAS) Brazil is a new shipyard
which is beginning to produce many of the vessels required for this
of the EAS Shipyard on Brazil’s east coast began in mid-2007 and on
completion it will be the largest shipyard in the southern hemisphere.
It will have a drydock measuring 400 metres long and 73 metres wide and
have a ship production capacity of 160,000 tons. The shipyard is
nearing completion but EAS has already received orders to design and
build ten Suezmax tankers.
|Suezmax modelled in Maxsurf and ShipConstructor (Enlarge)|
The Suezmax vessels are part of a batch of 26 ships to be built in the
first phase of the Program of Modernization and expansion the
Transpetro fleet. Transpetro is a subsidiary of Petrobras, the national
oil company of Brazil.
The use of Maxsurf and ShipConstructor by
EAS is being supported by our new Brazilian partner, Sincronia.
Developers of the IFM engineering document management system, Sincronia
are specialists in enterprise IT systems for offshore and shipbuilding
EAS are using Maxsurf, Rhino, Hydromax, Hullspeed and Seakeeper for their design work.
Maxsurf Subscription Program
The Maxsurf subscription program has been adopted by the majority of
our users to ensure that they automatically receive any updates to
Maxsurf as soon as they become available. The subscription program also
makes you eligible to receive an unlimited amount of technical support
via email, telephone or fax. When renewal time comes around, the
subscription lets you pay one annual fee for all of the programs you
own and will normally give you a major upgrade as well as any minor
updates during the year. Upgrades are delivered online and minor
updates are are also occasionally available for download.
|Docking Assembly and Properties Windows (Enlarge)|
Tips and Tricks
When dragging the Assembly or Properties views, if you drag and drop
them on to the centre blue icon, then both views are displayed in the
same location with a tab at the bottom to switch between views. This
maximises the screen space to display your assembly tree.