Flexible connector is the most important jointing component of a multiple-module floating platform, which determines the global behavior and safety of the platform by coupling or releasing some degree of freedoms between adjacent modules. Thus, applicable design and assessment techniques of flexible connectors need to be developed for design of a multiple-module platform that differs from design of typical offshore platforms. Focusing on the double-module semisubmersible platform, which will be firstly constructed and located near some island and reef in China, this paper gives the configuration of the hinge-type flexible connector actuated by the hydraulic cylinder. The equivalent structural stiffness of the connector is derived analytically treating the connector as a spring. Based on the three-dimensional hydroelasticity, more than ten modes of the platform from survival sea states are given and the directional loads of springs are obtained. Then the model test of the double-module platform is performed in wave basin with the scale ratio of 1:20. It can be found that numerical results of connector loads are basically more conservative than the experimental ones. Afterwards, the three-dimensional refined finite element model of the connector is established to evaluate the structural safety of the connector loaded by ultimate directional forces, in which the contact and friction between the shaft and the bearing is considered. Then the prototype loading test on the platform part including one complete connector is carried out. The experimental results agree well with numerical ones that validate the analysis methods for loads and structural safety of connectors. The design and assessment approach for connectors proposed in this paper have been used in practical design phases of the first double-module semi-submersible platform and will also provide useful technical tools for engineering development of further connectors used in multiple-module platforms.
To improve the comprehensive support capability of various ships and planes in deep and open sea, the very large floating structure (VLFS) with total length of one to three kilometers is always needed. Construction has to be carried out with modules made on land (e.g. 300m in length for every module) from a feasible view. And the multimodule conception could also be used in small or medium scale floating platform for scientific experiment and so on. Thus, the reliable connecting system is required, with which multiple modules are assembled at sea (Miguel, et al., 2015). From the angle of restricting relative motion of platform modules, the types of connectors are divided into two parts: one is rigid connector and the other is flexible one. When the rigid type of connector is used, the long platform is subjected to huge wave-induced loads that increase significantly the safety risk, and thus recent researches mainly focus on the flexible connector (Yu, et al., 2003).
