Objectives Against the backdrop of global warming, maritime activities in the Arctic region are increasing, and polar vessels inevitably encounter ice loads during navigation. A precise understanding of the deformation characteristics and failure mechanisms of hull plate structures under ice loads is crucial for ensuring the safe navigation of polar vessels. However, significant gaps remain in existing research, particularly regarding initial hull damage and the mechanisms of repeated ice loads. Based on this, this study aims to deeply explore the mechanical response characteristics of hull plate structures under ice loads, focusing on key scientific issues such as initial damage effect assessment and repeated ice load mechanisms, providing theoretical and technical support for the design of anti-ice structures and the safety assessment of polar vessels.
Methods A repeated compression test on steel hull plates and ice was conducted using a simplified plate model based on the actual bow shoulder structure, with some specimens pre-fabricated with initial defects to simulate real service damage. During the test, triangular pyramid ice models were prepared using the filling-freezing method. A total of 12 test cases were designed to systematically examine the effects of variables such as plate thickness, stiffener arrangement, defect direction, and position offset. The plate was pressed vertically at a constant speed of 6 mm/min to repeatedly compress the ice. High-precision sensors were used to measure displacement, force, and strain in real time, while the plastic deformation of the structure was recorded after each loading cycle to fully characterize the structural response under ice loads.
Results The results show that plate thickness has a significant impact on structural strength. As plate thickness increases, the slope of the compression force-displacement curve increases, while the loading displacement at ice failure significantly decreases. Although the arrangement of stiffeners can effectively enhance anti-ice compression strength, their ability to compensate for strength reduction caused by longitudinal defects is limited. Notably, when the defect location aligns with the ice load area, especially for longitudinal defects, significant stress concentration occurs at the root, leading to defect propagation. A comparative analysis showed that under the same load conditions, transverse defects exhibit higher load-bearing capacity than longitudinal defects. Additionally, offsetting defects significantly alters stress distribution: a 200 mm longitudinal offset of a longitudinal defect can reduce root stress by about 74%, while a 75 mm transverse offset of a transverse defect can increase root stress to 202 MPa at one end while reducing it to 66 MPa at the other end. After the first loading, plastic deformation generally occurred in the plates, with plates of lower initial strength exhibiting greater strength improvement during the second loading, even potentially surpassing those with higher initial strength.
Conclusions The study reveals the structural response characteristics of plate structures with initial damage under repeated ship-ice compression scenarios, providing valuable references for the design and evaluation of ice-resistant structures polar vessel structures.
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