Ropes are critical components for mooring ships and offshore floating structures under periodic axial loads. To investigate the tensile properties and stiffness characteristics of deep-sea mooring polyester ropes, they are categorized into three stages: preloading, initial installation, and aging. Initially, the tensile properties of the ropes under static loads are examined, quantifying strain and reversible elongation rates at each stage and comparing mechanical properties of polyester ropes with those of nylon ropes. Subsequently, creep coefficient solution tests under varying tensions are designed, establishing a quasi-static stiffness empirical equation with consideration of the rope creep coefficients. Experiments have shown that the mooring ropes still undergo reversible elongation after unloading, and sufficient break-in period of the ropes can reduce their inherent deformation and increase their structural stability. Static stiffness of the ropes increases with loading time and force until it reaches a constant value. Polyester ropes have greater stiffness, smaller deformation and more stable structure than nylon ropes, making them more suitable for deep-sea mooring. The findings enable comprehensive analysis of rope stiffness evolution throughout its service life, thereby offering references for reasonable design of deep-sea taut-line mooring systems.

Polar heavy icebreaker is the key supporting equipment for polar merchant shipping, rescue support, scientific investigation and resource exploitation. The polar heavy breaker deserves special consideration in the application of high-strength steel and other special materials, the structural safety assessment under ice load and the hull structural layout, due to the high ice load compared with the medium and low ice class polar ships/icebreakers. The previous structural design experience for medium and low ice class polar ships cannot be arbitrarily applied to the polar heavy icebreaker. The structural design and evaluating experience of a PC2 polar heavy icebreaker that was developed by Marine Design & Research Institute of China (MARIC) are summarized. It focuses on the application of high strength steel for the ice belt structure, the application requirements and characteristics of composite steel plate for the ice belt outer plate, the impact of the non-linear evaluation technology on the ice belt scantlings, and the distribution of the ice-induced shear/bending moment and its influence on the structure in non-ice-belt regions, such as the inner platform of the main ship and the side hull of the bridge. It presents the structural design characteristics of the polar heavy icebreaker and the main differences between the polar heavy icebreaker and the medium and low ice class polar ships/icebreakers in terms of the overall structural layout and the design and evaluation of the ice belt structure. With the increase of the ice class, it is believed that the ice load not only affects the outer plate and its attached components in the ice belt region, but also has significant impact on the material selection of the ice belt structure and the overall structural layout and design of the whole ship.