Experimental study and analysis on residual strength of ice strengthening structure in heavy icebreaker

Objectives Heavy icebreaker will experience a certain degree of permanent deformation of the ice strengthening structure after encountering over-designed ice loads. It is necessary to assess the residual strength of the ice strengthening structure after permanent deformation in order to ensure traveling safety. Methods A heavy icebreaker amidships side part of the ice strengthening structure is selected for model test, EH500 steel is used to make the plate frame model. High strength gypsum powder is used as the main raw material to make the non-refrigerated breakable model ice by mixing and pouring. The weak and strong members of the plate frame model are dynamically impacted by the free fall of the model ice, so as to make the test plate frame permanently deformed, and then the quasi-static loading test is carried out at the weak members of the plate frame model with permanent deformation until the plate frame model is plastically collapsed to obtain the residual strength of the plate frame model. Finally, the whole test process is simulated by finite element software, and the residual strength of the ice strengthening structure is calculated by explicit dynamic nonlinear analysis method and compared with the test results. Results The error between model tests and numerical simulations is within 20%, and the maximum permanent deformation of the ice load at the weak member of the ice strengthening structure is larger than that at the strong member, which in turn leads to lower residual strength of the ice strengthening structure. Conclusions The research results reveal the effects of permanent deformation on the residual strength of the strong/weak members of the ice strengthening structure of the heavy icebreaker and the damage form of the limit state, which can provide reference for the structural design and strength assessment of heavy icebreakers.