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Dynamic loads components

The Dynamic Load tab defines a list of individual dynamic loads applied to any structural model components (such as Lines, Floaters; Rigid Bodies, Buoys, etc) that may be used to define combined environments from the Combination matrix tab.

Warning

Dynamic loads can only be accounted for within dynamic analyses in the time-domain. These dynamic loads are not accounted for within dynamic analyses in the frequency-domain.

The Dynamic Load tab includes the following items:

  • Number of dynamic loads: The number of Dynamic Loads components must be set with the spin box located in the upper right corner of the tab. You may either use the up/down arrows to setup the number of Dynamic Loads, or input any value using your keyboard and then pressing the ENTER key. Pressing the ENTER key confirms the number of individual components to be included and generates the main Dynamic Loads data table with appropriate number of rows.

  • Insert new loads: Pressing this button inserts a new row in the main Dynamic Loads data table.

  • Remove selected loads: Pressing this button deletes the selected rows from the main Dynamic Loads data table.

  • Dynamic Loads data table: This table is used to define the Dynamic Loads data. This table includes 5 columns, as follows:

    • Name: This assigns names that will be used to refer to the Dynamic Loads components in the Combination matrix tab.

    • Object: Used to select the structural model component to which the Dynamic Loads will apply. Each cell in this column contains a drop-down list filled in with the names of all structural components available in the model (including lines, floaters, rigid bodies, buoys, etc).

    • Location: Used to select the point on the structural component at which the Dynamic Loads will apply. Each cell in this column contains a drop-down list filled in with the list of points that is available with the selected structural model component (e.g. including the COG and all fairleads/hang-off points for Rigid bodies, Buoys and Floaters, and including all primary connection points for Lines).

      Warning

      Dynamic Loads would have no effect on the structural component in case this latter is assigned a boundary condition that would prevent it from moving under the action of the loads. The user interface does not raise any warning message in case the node to which the loads apply is assigned a boundary condition.

      Note

      Loads applied to fairlead/hang-off point are automatically transferred to the master node of the structural component, properly accounting for lever arm effects and resulting moments.

    • Axes: This selects whether loads sub-components refer to the global coordinates system or to the local coordinates system associated with the node on which the loads apply.

    • File: Path and name of the external data file providing the time-history of the dynamic loads along the 6 degrees of freedom. The path could either be defined by typing the text or by browsing to the file after clicking the button placed on the right hand side of the cells. See the *FLOAD and *FLOCLOAD keywords for details on the external file format.

    Note

    The format of external file is as follows :

    T0 FX FY FZ MX MY MZ
    T1 FX FY FZ MX MY MZ
    T2 FX FY FZ MX MY MZ

    Tn FX FY FZ MX MY MZ

    The number of lines is unlimited.

    FX FY FZ are the force components in N..
    MX MY MZ are the moment components in N.m.

Note

During the ramptime period of the dynamic analysis, the prescribed dynamic loads are multiplied by a factor t/RAMP in order to provide a progressive application of the prescribed loads (see *RAMPTIME keyword) at the start of the dynamic analysis.

An example of Dynamic Load tab is shown below: