This study presents an upper bound plastic limit analysis for predicting draganchor trajectory and load capacity. The shank and fluke of the anchor are idealized assimple plates. The failure mechanism involves the motion of the anchor about a centerof rotation, the coordinates of which are systematically optimized to determine theminimum load at the shackle. For a given anchor orientation, the direction of theshackle force is varied to establish a relationship between the magnitude and direction ofthe shackle load. Coupling this relationship to the Neubecker-Randolph anchor linesolution produces a unique solution for the magnitude and orientation of the shackleforce. The anchor is then advanced a small increment about the optimum center ofrotation and the process is repeated. The upper bound method (UBM) provides apractical means to determine the trajectory of the anchor and the anchor load capacity atany point in the trajectory. To better understand of the anchor behavior, extensiveparameter studies were carried out varying the properties of the anchor, anchor line, andsoil. The UBM show good agreement with six full-scale tests covering several differentanchor types and centrifuge model tests.
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