Help with SACS Transportation Inertia Load analysis

Dear Colleagues,

Hi I am new with SACS, and am working on inertia loading generation with SACS tow module. I have some confusion with the notation system that SACS tow adopt.

Let's say we have conventional seakeeping coordinate system (X-surge, Y-sway, Z-Heave, with their corresponding rotation). For roll motion (+), the body inertia translation force will be in the opposite direction of the motion translation components. Hence, the inertia force should be in sway (+) and heave (+). However, the result from SACS tow suggests for such motion, the translation forces in sway (-) and heave (+) (see figure below). Anybody can help me to understand this? I could be wrong or lack of understanding in this case. Thank you for taking your time to read this problem, any help will be much appreciated.

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  • I didn't have you towinp file, but lst file shows you defined 5 load cases with roll+-, pitch +- and heave+. I suppose the first 4 have only roll/pitch angle and heav+ have only Z acceleration?

    The roll/pitch data specified in "Motion" command is the roll/pitch angle with heave acceleration.  Roll and pitch angle can be positive or negative, a positive roll angle means jacket and barge placed at location below, and hence it cause an acceleration in +Y direction with inertia load in -Y. You have question about heave force from load case "ROL+'" or load case "HAV+"?

    For a transportation analysis, both max and min roll/pitch angle (positive and negative value)should be considered together with a heave acceleration.

Reply
  • I didn't have you towinp file, but lst file shows you defined 5 load cases with roll+-, pitch +- and heave+. I suppose the first 4 have only roll/pitch angle and heav+ have only Z acceleration?

    The roll/pitch data specified in "Motion" command is the roll/pitch angle with heave acceleration.  Roll and pitch angle can be positive or negative, a positive roll angle means jacket and barge placed at location below, and hence it cause an acceleration in +Y direction with inertia load in -Y. You have question about heave force from load case "ROL+'" or load case "HAV+"?

    For a transportation analysis, both max and min roll/pitch angle (positive and negative value)should be considered together with a heave acceleration.

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