Abstract: To analyze the structural damage characteristics of the semi-submersible platform column structure under ship impact loads and establish a safety assessment method for the column, impact experiments and numerical simulations are carried out based on structural shakedown behavior. The characteristics of the bearing capacity and indentation of the stiffened plate under the state of pseudo-shakedown are analyzed based on the quasi-static penetration test and the dynamic repeated impact test. The hardening model of the material and the damage model based on the B-W fracture criterion are developed by conducting the tensile tests, and the numerical simulations of the impact tests of the stiffened plate are carried out. The established numerical approach is applied to the impact response analysis of the column, and the critical elastic deformation energy of the column is obtained. The mass and velocity characteristics that the impact ship should meet to ensure the structural integrity of the column are given. A preliminary safety assessment guideline for the column subjected to ship impact loads is proposed, which can provide a reference for the analysis and assessment of the crashworthiness of the semi-submersible platform column structure.