ABSTRACT

Very large floating structures are of great interest in the development of marine space and resources. In order to verify the key technologies in the research and development of very large floating structures, we deployed a double module articulated semi-submersible platform, and carried out long-term monitoring with a wave environment monitoring system and a mooring force monitoring system. Observed wave data were used as input for hydrodynamic analysis, the estimated mooring force was compared to the equivalent statistical measured value, and the impact of wind load, current load, and mooring pretension was investigated. Results demonstrate the reliability of our numerical model and suggest that, when wind and current loads are low, the pretension can be decreased to lessen the mooring force. The pretension adjustment has little impact on the level of the mooring force when wind and current load are high.

INTRODUCTION

Very large floating structures can be built as floating harbor ponds, tourist platforms, maritime airport runways, and offshore pastures by combining various functional modules. These structures are of tremendous relevance in marine space utilization and the development of marine resources. Due to their size, they are sometimes broken up into several modules and combined with connectors (Wu et al., 2021). As for the articulated multi-module platforms, their motion characteristics are somewhat different from the traditional single-module ones because the connectors release the relative rotation between modules. For the design of the mooring system, additional consideration needs to be given to the limitation of the relative rotation amplitude to prevent collision of the modules. The impact of the mooring system on the connector load should also be considered.

Scholars and engineers domestically and internationally have paid close attention to the research of the hydrodynamic performance of such multi-module floating platforms because of their great significance. Miao et al. (2021) and Sun et al. (2020) studied wave drift and slamming forces of a two-module platform using potential flow theory. Li et al. (2018) and Ding et al. (2020) analyzed the motion and inter-module connection load of a multi-module platform based on a three-dimensional hydroelastic method. Yu et al. (2019) carried out mooring design for a three-module semi-submersible platform. Ni et al. (2020) investigated multi-module platform's motion and mooring tension by hydrodynamic model tests and numerical simulations. A 2000m-long, eight-module platform that is anchored by a catenary was the subject of a hydrodynamic analysis by Ni et al. (2020) using a time-frequency domain computation method.

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