The influence of a quadratic viscous drag nonlinearity in multi-point
mooring systems is examined in this paper. These systems are character
ized by a nonlinear restoring force and a coupled wave-structure excit
ing force. Stability analysis of system response and its corresponding
Poincare map define domains of primary and subharmonic resonances and
reveal the existence of coexisting nonlinear solutions. Local and glo
bal tangent and period doubling bifurcations identify possible routes
to chaotic motion and their controlling parameters. Thus, complex dyna
mics are obtained semi-analytically resulting in identification and co
ntrol of the drag-induced instabilities which are not attainable by eq
uivalently linearizing the hydrodynamic drag force.