Stochastic response of a two DOF articulated tower

In a previous paper [P. Bar-Avi and H. Benaroya, Journal of Sound Vibration 190, 77-103 (1996)], the response of an articulated tower in the ocean subjected to deterministic and random wave loading was investigated. The tower was 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 this paper, which is an extension of the previous one, the tower is modeled as a spherical pendulum having two angular degrees of freedom. The tower is subjected to wave, current, and vortex shedding loads. Geometrical non-linearities as well as non-linearities due to wave drag force, which is assumed to be proportional to the square of the relative velocity between the tower and the waves, were considered. The governing coupled differential equations of motion are highly non-linear, and have time-dependent coefficients. The tower's average response is evaluated for uniformly distributed random fluid constants C-D, C-M, C-L, friction coefficient mu and current direction alpha. This is accomplished computationally via Monte-Carlo simulations with the use of 'ACSL' software. The influence on the tower's response of different parameter values is investigated. (C) 1997 Elsevier Science Ltd.