MAESTRO FAQ

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.

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