Stochastic Nonlinear Dynamics of Floating Structures
Abstract
This paper presents studies on the response of an articulated tower in the ocean subjected to deterministic and random wave loading. The tower is modeled as an upright rigid pendulum with a concentrated mass at the top and having one angular degree of freedom about a hinge with coulomb damping. In the derivation of the differential equation of motion, nonlinear terms due to geometric (large angle) and fluid forces (drag and inertia) are included. The wave loading is derived using Morison's equation in which the velocity and acceleration of the fluid are determined along the instantaneous position of the tower, causing the equation of motion to be highly nonlinear. Furthermore, since the differential equation's coefficients are time-dependent (periodic), parametric instability can occur depending on system parameters such as wave height and frequency, buoyancy, and drag coefficient. The nonlinear differential equation is then solved numerically using 'ACSL' software. The response of the tower to deterministic wave loading is investigated and a stability analysis is performed (resonance and parametric instability). To solve the equation for random loading, the Pierson-Moskowitz power spectrum, describing the wave height, is first transformed into an approximate time history using Borgman's method with slight modification. The equation of motion is then solved, and the influence on the tower response of different parameter values such as buoyancy, initial conditions and wave height and frequency, is investigated.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 03, 1994
- Accession Number
- ADA284331
Entities
People
- Haym Benaroya
- Patrick Bar-avi
Organizations
- Rutgers University Department of Mechanical and Aerospace Engineering