Restart Analyses |
 
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Restart Analyses |
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A given design condition will typically require a structure to withstand a combination of static and dynamic loads and displacements. In performing a Flexcom analysis for these inputs, it should be possible to apply all static and dynamic loads and displacements in a single dynamic run. However, this is frequently not possible, and is rarely desirable. A better option is to invoke the program Restart facility, whereby you can specify that a particular analysis is to be restarted from a previous run, to build up to the full dynamic solution in stages. In a restart, the structure configuration at the end of the preceding analysis becomes the starting configuration for the restart. New loads or displacements are combined with those in the preceding run, and the structure response to the combined loading is found in a static or dynamic solution.
The major application of this facility is in starting a dynamic analysis from a static configuration due to gravity, buoyancy, current and applied constant loads and displacements. The advantage of this procedure in the time domain is that it minimises the influence of initial transients associated with the application of the dynamic loads, with a consequent saving in CPU effort in the dynamic run. In terms of the frequency domain, a necessary prerequisite is that the dynamic analysis restarts from a converged static solution.
The use of restarts is also frequently mandatory in the analysis of flexible risers and mooring systems. Because of their low bending stiffnesses these systems depend largely on tension to resist applied loads. When static loads are applied in an initial step or steps, the system develops a resistance to lateral loads such as those due to waves and current, which are then applied in restart runs.
Further information on this topic is contained in the following sections:
•Restart Types outlines the two basic restart types, determined by changes in loads and boundary conditions.
•Data Specification in a Restart categorises the various program inputs in terms of which parameters can and cannot be altered in a restart.
•*RESTART is used to indicate that an analysis is to be restarted from a previous run.
If you would like to see an example of how this keyword is used in practice, refer to any of the standard Flexcom Examples.