A Laplace-domain method for motion response estimation of floating structures based on a combination of generalised transfer function and partial fraction

ABSTRACT

A Laplace-domain method is proposed to predict time-domain motion responses of floating structures. As a theoretical contribution, two techniques of generalising transfer functions of floating structures (GTFF) are developed, which are symbolic-based and Fourier transform-based techniques. Three cases are employed in this study: The first case involves a single degree-of-freedom system to demonstrate the correctness of the derived GTFF, which is assumed to have a purely analytical retardation function. The second case involves a truncated cylinder subjected to random waves that are defined by a Jonswap spectrum. Numerical results show that the symbolic approach simultaneously offers a perfect estimation of the transfer functions of a system, while the inverse Fourier-transform-based approach has some discrepancies at the first short parts of the phases. To further investigate potential applications, a floating platform is employed, and comparisons are drawn by using the commercial software SESAM, which found consistently estimated motion responses.

KEYWORDS:

• Laplace-domain response
• floating structure
• transfer function
• Fourier transform
• SESAM

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge the financial supports of the National Natural Science Foundation of China (grant no. U1806229), and the Taishan Scholars Program of Shandong Province.