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*Friction

Purpose

To specify longitudinal and transverse seabed friction stiffnesses.

Theory

Refer to Seabed Modelling in Modal Analysis for further information on this feature.

Keyword Format

One line containing the friction stiffness values:

Longitudinal Stiffness, Transverse Stiffness

This keyword is only relevant where the initial static analysis has at least one non-zero seabed friction coefficient.

Table Input

Notes

(a)This table is only relevant for a modal analysis, where the initial static analysis has at least one non-zero seabed friction coefficient.

(b)You can model friction in a modal analysis using either a total restraint, or a partial restraint modelled using a spring stiffness. For more information, please refer to Motion in the Plane of the Seabed.

(c)By default, seabed friction continues to be modelled in the same way as in earlier program versions (the so-called Fully Restrained Model). This corresponds to the situation where both stiffness entries in this table are zero.

(d)To apply a partial restraint in either the longitudinal or transverse direction, you input a non-zero stiffness in this table in the appropriate direction.

(e)Note however that a non-zero value is immaterial and unused if the corresponding friction coefficient was zero in your initial static analysis. In that case, free motion in the appropriate direction is permitted.