The impact of the shape of the spectral density of random wave disturbance on the vibrations of a fixed sea-based offshore platform

摘要

It was generally assumed earlier in the study of the impact of random wave disturbance on fixed sea-based offshore platforms (FSOP) that the spectral density of wind-driven gravitational waves has the shape described at the Second International Ship Structures Congress held in Delft, Netherlands, in 1964. Since that time, a number of analytical expressions for the description of the spectral density have been suggested. In this paper we study the amplitude of the FSOP vibrations as a function of the shape of the spectral density in the framework of a model with one degree of freedom. Four shapes of the spectral density are considered. We compare the levels of the FSOP vibrations caused by wave disturbance with these shapes of the spectral density with each other and with the level of vibrations caused by harmonic wave disturbance. It has been established that the off-resonance amplitude of the FSOP vibrations depends mostly on the average wavelength and wave height (or on related parameters such as the average frequency and the standard deviation). In the vicinity of resonance, the amplitude of vibrations was proved to noticeably depend on the shape of the spectral density.