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[Shuangxing Du]

Please see Aqwa Theory Manual, Section 10.2,

For an installed tether, between the vessel end of the tether and its corresponding vessel attachment point, three spring stiffnesses (, , and ) are defined as the inline stiffness and two rotational stiffnesses about the TEA y- and z-axes respectively. These are used to determine the relative translational displacement in the TEA x-direction and rotations about the TEA y- and z-axes between the vessel end of the tether and the vessel attachment point. The relative translational displacements in the TEA y- and z-axial directions are set to be zero at the vessel attachment point.

Similar to the vessel end of an installed tether, three spring stiffnesses ( , , and ), between the anchor end of the tether and the corresponding fixed point on the sea bed, are defined as the inline stiffness and two rotational stiffnesses about the TEA y- and z-axes. The relative translational displacements in the TEA y- and z-directions are set to be zero at the anchor point.

And Aqwa reference manual, Section 19.19.2.

For installed tethers, the spring stiffnesses are the inline/vertical stiffness and the two rotational stiffnesses (about the local tether Y- and Z-axes) at the ends of the tether. Default values of 1.0E15 are used, if this data record is omitted. A default value of 1.0E15 for the inline stiffness is used if the 1st field is left blank or a negative or zero values is input. For the rotational fields, any value may be entered (except negative values which will be set to zero).