Makers of MOSES - The Final Answer in Marine Simulation
What Is New In Rev. 5.03

General Changes:

REV 5.03 began as a minor release, but somewhere along the development process became something quite a bit more substantial. The major new feature is the addition of a capability to extract structural modes of vibration, and (an extra price option) to use these modes as generalized co-ordinates in traditional MOSES analyses. With the modes as generalized co-ordinates, the deformation and deformation inertia are automatically included in any MOSES analysis.

Generalized Coordinates:

A side benefit of generalized co-ordinates is that virtually all of the algorithms have been sharpened. There is always a trade off between more "sophisticated" algorithms which require more computation per step and "cruder" ones. In many cases, the "crude" algorithm will yield as good a solution quite a bit faster. As the number of degrees of freedom increase, however, the more sophisticated normally wins. This is why you can now get better answers with the same time steps or model refinement, or get as good an answer with a larger time step or less refined model. As an example, the Newmark method is now the default for time domain simulation, and now iterates within a time step to a specified tolerance. Added mass and damping matrices are computed more accurately, and environmental force derivatives are now added to the stiffness matrix.

Compartments:

Another major change is the way in which compartments are treated. The software can now deal with compartments containing fluids of two different specific gravities. This is particularly useful when simulating a compartment that gets filled at different times at different locations. Perhaps the first time a compartment is partially filled is at an inland harbor location, using fresh water. The second time could be at an offshore site, using salt water. Also, compartments can now be drained or filled according to valve location and internal pressure in the compartment. As a result, the -INT_PRE option has moved from &DESCRIBE COMPARTMENT to &COMPARTMENT. The -CONTENTS option has also been removed from &DESCRIBE COMPARTMENT. The specific gravity of contents is now stated with the -PERCENT, -FRACTION or -AMOUNT options of the &COMPARTMENT command. The &COMPARTMENT command has been enhanced to include the new flags -INITIAL, -ADDITIONAL, -SIMPLE, and -OPEN_VALVE, and a new option, -COMPRESSOR has been added to account for a compressor attached to the compartment. As a result of this work with compartments, the "weight" of a body has changed. In the past, the weight included the ballast in the compartments. It now is only the "dry" weight. A new concept, apparent weight, means what weight used to mean. As a result, the string functions &PART and &BODY with action types of CG, WEIGHT and RADII now return only the "dry" values of a system, excluding the effects of compartment contents. New action types of A_CG, A_WEIGHT, A_RADII have been added to &BODY, which return the "apparent" system values including the effects of compartment contents.

Panel Mapping:

Experience with several engineering analyses showed quite quickly that the "automatic" mapping from panels to nodes was not always adequate. As a result, two new commands have been added to give the user quite a bit of control over the mapping.

Environment:

Another basic change was with the environment. In the past, one had a single sea spectrum and a single current profile. This proved limiting. As a result, one can now have up to 5 of each. For current, this results in being able to specify the velocity and direction completely as a function of depth. For seas, we have a much generalized Ochi Hubbel type of definition where each spectrum can have its own direction, and a GAMMA.

Mooring Line Fatigue:

The ability to assess fatigue of mooring lines is now available. This caused quite a bit of re-thinking on what we report and on how SN curves are used. To begin with, we included the API WIRE and CHAIN "SN" curves. But since a single mooring line can be composed of both, some way of defining the curve to use for each segment was needed. Second, these curves are not SN curves but T/TB curves. Again, a way to define the breaking strength of each segment was needed. Finally, a mechanism was needed to allow the user to define this new type of "SN" curve. The result of all of this is the new options -B_TENSION and -C_SN on the connector class definition. Also, the &REP_SELECT command now has a way of defining and later using SN curves of both the traditional type and the tension type. The concept of cycle counting is closely related to fatigue, and two new commands have been added to allow one to count cycles of mooring line tension and beam moments and shears. Also, since we now have the breaking tension, all connector force reports contain the critical ratio of tension to breaking tension.

Joint Crushing:

The software can now perform joint crushing checks. This is done with a type of CRUSH on the JOINT command in the post-structural menu. Finally, the title and subtitle are now remembered from one program execution to the next.