| The articulated tower platform(ATP) is the a kind of compliant platform designed for water depths of 100 to 500 m, it is used as single point mooring or as loading terminals, control towers, seabed installation facilities. The ATP suffers from nonlinear ocean environment loads, the study of swing motion and motion stability of ATP is very important for safety of the platform. In this paper, the theory and method of nonlinear dynamics are adopted to study the nonlinear dynamic behavior and motion stability of the ATP under complicated environment loads. In addition, the motion behavior of single point mooring articulated tower and the impact property of mooring force are studied. The main work and the conclusions obtained are as following:(1) The research development and current state of the nonlinear dynamics of ATP at abroad and home is summarized synthetically. The study direction and key problems of the thesis are presented.(2) The dynamics model of rigid body of ATP is put forward considering non-elastic tower, the hydrodynamic force is evaluated for the ATP by using Morison formula, the highly nonlinear motion equation is established according to Lagrange principle. Sup-harmonic resonance, sub-harmonic resonance, combination-harmonic resonance and chaos motion of ATP were investigated using numerical method with considering wave loads and combined wave-current loads respectively. The results show that the sup-harmonic resonance of orders 2,3,5…and 2 v m +vn combination-harmonic resonance will occur under wave loads; sup-harmonic resonance of orders 2,3,4,5…, v m + vn and 2 v m +vn combination-harmonic resonance will occur under combined wave-current loads; sub-harmonic resonance of order 1/2 was found in certain case under wave loads; Chaotic motion was found under high frequency wave excitation.(3) Considering elastic deformation of the tower, the hydrodynamic force is evaluated at the instantaneous position of ATP using Morison formula, the partial differential equation of swing motion is established. The nonlinear response of ATP is calculated by Galerkin's method. The results show that the second mode of ATP arises sup-harmonic resonance of orders 2,3,4 , and the unsymmetry of the motion of ATP is found under wave excitation. The dynamical response of ATP and the moment variety of tower are analyzed under different environmental loads by the finite element method, and the simplified model is validated in this paper.(4) The calculation methods using incremental harmonic balance method, Floquet theory and incremental arc length method are presented for nonlinear dynamical response of ATP-Tanker considering piecewise linear restoring force and square damping. Sup-harmonic, sub-harmonic, harmonic, combination harmonic response, amplitude frequency characteristic and the behaviors of bifurcation and chaos are studied. Three kinds of chaotic motion caused by period doubling bifurcation in this system are verified by the max Lyapunov exponent diagram. The coexistence of chaos and stable period motion, and the sensibility of system motion depending on the initial value are explained by the interpolated cell mapping method.(5) Based on the response of ATP-Tanker system, the varying characteristic of mooring force is studied. It is found that there are many different mooring force responses for the same set of system parameters, the abrupt change occurs easily in the motion of the system when it is perturbed and the mooring force response jumps among the several different values. This can primarily explain the mechanism of the abrupt change of the mooring force for the ATP-Tanker system.
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