**With
regard to the section numbering and spacing for printing the summed
vertical loads, shear forces and bending moments, could you please
clarify whether the station position (i.e. xmin for the first internal)
is at the aft end or the center of the interval for the purpose
of calculating longitudinal centers.**
The
station spacing is provided in ITEM 5 of the structure parameters
group of the Data Preparation manual. The beginning location is
provided in ITEM 8 and 9 of the structure parameters group of the
data preparation manual. From this information MAESTRO generates
the sum of forces in y- and z- directions as well as shear force
and bending moments. The values are reported at the location indicated
by the station locations. Station 0 is at the x-location indicated
in ITEM 8 and 9, station 1 at the previous station plus the station
spacing in ITEM 5, and so on. In case the x-location of a node falls
between two stations then the nodal force will be allocated to the
two surrounding stations weighted with respect to the distances
to the stations.
**EXTERNAL BEND MOMENT
AND SHEAR FORCES : APPLICATION WITHOUT CHANGING HYDROSTATICS.**
**I am attempting to apply design
hogging and sagging bending moments to a model of a complete ship
in MAESTRO version 7.1.1. In order to do this I initially applied
the following load sets to the model, **
i |
**Group XIX(
c) immersion and wave load data for a hogging wave** |
ii |
**Group XIX(
c) immersion and wave load data for a sagging wave** |
iii |
**Group XIX(
h) weight distribution** |
And combined (i) and (ii), and (iii), to produce hogging and sagging
load cases respectively.
**I then interactively modified the
draught and trim in the immersion data to close the two resultant
bending moment diagrams at the forward end and achieve a balanced
model.**
**In order to obtain the required
design bending moments, which include a factor for probability of
exceedance, I then included a partial safety factor for each load
case in Group XX (b).**
**Is there a valid method for applying
design bending moments, and that increasing both the buoyancy and
weight distribution does not result in a deeper draught and hence
hydrostatic loads on different panels? Does the PSF just factor
the total load due to buoyancy and weight?**
**How are the partial safety factors
applied to each load case?**
The above approach is considered appropriate
for a full-length model where there are no applied cut section loads
introduced. In this case the closure of the bending moment at the
opposite end is a consequence of the full model being balanced.
Note that the forces due to the restraint, if any, are not included
in the table provided in the output file. The partial safety factor
is simply applied to the loads and does not influence any parameters
such as immersion, roll, pitch, etc.
**MASS : APPLICATION TO 3.D NODES.**
**Can Maestro apply mass to a set
of 3-D nodes so that these nodes will receive forces due to accelerations
being applied to the model? Can the user get access to these forces?**
Yes, Maestro allows the user to specify
an amount of mass to be allocated to a set of nodes defined across
the modules in the model. This data can be specified in Maestro
Modeler under the group dialog called 'Nodes'. The nodes are selected
interactively by graphically picking any number of nodes. The mass
value entered will be distributed evenly to the nodes. The mass
will impact the selected nodes according to the inertia forces reacting
as a result of the accelerations defined in the particular load
case. The total load vector is inclusive of all forces including
inertia forces.
Should the user wish to print only
the resulting inertia forces due to a particular mass affecting
a set of nodes it can be done by creating a separate load case using
this mass as the only mass in the model. With an output level 4
Maestro will then print the forces in the load case. The user can
also plot these forces in the Maestro Graphics and inquire on their
values.
Alternatively, the user can select
the more advanced group feature called BAY&SETS. Here the mass
is given a CG and a set of nodes which can selectively acts as tension
only, or pressure only. In addition mass can be distributed to the
nodes in ratios defined by the user. The forces due to BAY&SET
can be selectively inquired on whether in a separate load case or
as part of a load case involving other loads.
**PRINTING : SUMMED LOADS, SHEAR,
BENDING MOMENT.**
**With regard to the section numbering
and spacing for printing the summed vertical loads, shear forces
and bending moments, could you please clarify whether the station
position (i.e. xmin for the first internal) is at the aft end or
the center of the interval for the purpose of calculating longitudinal
centers.**
The station spacing is provided in
ITEM 5 of the structure parameters group of the Data Preparation
manual. The beginning location is provided in ITEM 8 and 9 of the
structure parameters group of the data preparation manual. From
this information MAESTRO generates the sum of forces in y- and z-
directions as well as shear force and bending moments. The values
are reported at the location indicated by the station locations.
Station 0 is at the x-location indicated in ITEM 8 and 9, station
1 at the previous station plus the station spacing in ITEM 5, and
so on. In case the x-location of a node falls between two stations
then the nodal force will be allocated to the two surrounding stations
weighted with respect to the distances to the stations. |