Dynamic Response Analysis of Small-Scale Floating Structures under Level Ice Actions

The design and safety assessment of small floating structures in ice-covered seas has become an increasingly important and widely recognized topic in cold region engineering. Ice loads are the primary controlling loads for offshore structures in ice-covered regions, and the fracture processes and characteristics of level ice interacting with structures are closely related to the structural type. The dynamic response of small floating structures under level ice is particularly complex. Based on prototype tests of small floating structures, this study investigates the motion behavior, ice-load response, and sea ice fracture processes and characteristics of these structures. The results demonstrate that the interaction between sea ice and the floating structure exhibits pronounced periodicity. Under thin-ice conditions, the maximum inclination is approximately 18°, whereas under thick-ice conditions, the maximum inclination can reach up to 60°. Based on the relationship between inclination and ice force, the corresponding maximum vertical ice forces are estimated to be approximately 12 and 31 kN, respectively. The average ice-force cycle under thin-ice conditions is significantly shorter than that under thick-ice conditions. Based on the motion responses extracted from the prototype tests and video observations, the ice–structure interaction process is classified into three stages: ice-load application, ice-load release, and self-oscillation of the floating structure. In addition, a simplified dynamic ice-force model is established, and key parameters are obtained through statistical fitting. The breaking length coefficient is determined to be 4.0, while the self-oscillation coefficient (0.651) and the ice -force coefficient (0.184) are both found to be consistent with normal and log-normal distribution patterns. These findings provide practical guidance for the ice-resistant design and safety evaluation of small floating structures in ice-covered seas.