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Quasi-static loads components

The QS Load tab defines a list of individual quasi-static 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.

The QS Load tab includes 2 sheets labeled Loads List and Quasi-static Evolution.

Loads list data sheet

The Loads List sheet includes the following items:

  • Number of quasi-static loads: The number of QS 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 QS 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 QS loads data table with appropriate number of rows.

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

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

  • QS loads data table: This table is used to define the QS loads data. This table includes 12 columns, as follows:

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

    • Object: Used to select the structural model component to which the QS 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 QS motion 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

    Quasi-static 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.

    • Evolution: This option sets the quasi-static evolution that is to be associated with each QS loads component. The following items are available:

    • Default: Selecting this option instructs the software that the quasi-static evolution which is defined in the Quasi-static evolution tab shall be used.

    • Linear: Selecting this option supersedes the quasi-static evolution that is defined in the Quasi-static evolution tab. "Linear" means that the QS loads is applied progressively with a linear ramp between the first quasi-static step (i.e. no load at step 0)and the last quasi-static step (i.e. complete load at the last quasi-static step).

    • User defined: Selecting this option supersedes the quasi-static evolution that is defined in the Quasi-static evolution tab. "User defined" allows selecting the rate of QS load amplitude that is considered as a function of the quasi-static step.

    • Edit button: This button is only enabled in case the user-defined QS evolution is set as "User-defined". Pressing the button raises a window allowing to set the data related to the user-defined evolution.

    • 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.

    • FX (N): Defines the quasi-static force along the global or local X-axis.

    • FY (N): Defines the quasi-static force along the global or local Y-axis.

    • FZ (N): Defines the quasi-static force along the global or local Z-axis.

    • MX (N.m): Defines the quasi-static moment about the global or local X-axis.

    • MY (N.m): Defines the quasi-static moment about the global or local Y-axis.

    • MZ (N.m): Defines the quasi-static moment about the global or local Z-axis.

Quasi-static evolution data sheet

The Quasi-static Evolution tab is used to set an evolution law (i.e. the ratio of load applied as a function of the quasi-static load step) that will be common to all QS loads components.

  • Linear means that the QS load is applied progressively with a linear ramp between the first quasi-static step (i.e. no load at step 0) and the last quasi-static step (i.e. complete load at the last quasi-static step).

  • User defined allows selecting the rate of QS load amplitude that is considered as a function of the quasi-static step.

An example of QS Load tab is shown below: