The mode response of a steel truss bridge was analyzed by ANSYS and its seismic responses under transverse and longitudinalexcitation were calculated using time-history analysis function.
In the present paper, the resonant response of a vertical mooring-line in case of neutrally buoyancy, for a given harmonic longitudinalexcitation, is discussed. The law of stress-strain is nonlinear.
A nonlinear parametric excitation equation is obtained for ships in longitudinal waves, and the dynamic stability is analyzed when the natural frequency of heave and roll are approximately equal.