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The researches of the anti-collision characters of a semi-submersible column and its capability of surviving in severe sea state after collision accident are completed.Three collision cases are designed.A 5000-ton vessel hits the semi-submersible column in transversal,longitudinal and oblique directions.Numerical simulation technique is used to finish the analysis,and anti-collision characters of the semi-submersible column are summarized through the summary of the results,including curve of collision force vs.penetration,curve of energy absorption proportion and the structural damages.It is pointed out that the column show a distinctive character when the contact area is large at the beginning of the collision.Although the column structures suffer obvious distortion,there is no rupture of outer shell,which means the column can sustain such kind of collision.Taking advantage of the direct calculation method with finite element technique,the global strength of the semi-submersible is verified to assess the influence of structure damage by the collision on the semis survival capability in severe sea state.The structure damage caused by the collision is taken into consideration in the FE models.The code SESAM is used to do the calculation through the design wave method.Several assumptions are made to realize the comparison between collision cases.It is found that the collision influence is restricted within the bound of structural components around the collision zone.The collision damage caused by the striking of the 5000-ton vessel will not bring a serious threat to the global strength capability of the semi-submersible.