FREQUENCY DOMAIN ANALYSIS OF TIME-VARIANT TENSILE AXIAL LOADING CYLINDERS UNDER RANDOM WAVE FORCES

摘要

A cylinder is modeled as a Bernoulli-Euler beam subjected to a time-variant axial loading at top end and both ends are assumed as hinged. The axial tension consists of a constant static part and a harmonic dynamic part. The wave force is formed using a semi-empirical Morrison equation. Waves are assumed to be random and their heights comply with the JONSWANP spectrum. A frequency domain method is developed for such linear systems with periodical time-varying parameters based on the pseudoexcitation method. The standard deviations of structural displacement responses are calculated,and the influence of time-variant tension frequency,i. e. the parametric excitation frequency,on such responses is discussed.