Plastic design methods are applied to determine the load carrying capacity of the shell structure of an ice-going ship. The main object is the behaviour of the ice-strengthened frame, when the yield stress level is reached and exceeded. In the first part of this report quite simple analytical methods are used to study the various collapse mechanisms of the frame. The ultimate strength of the individual parts of the frame is determined and the total load carrying capacity is then calculated. The possibility of the lateral collapse of the frame is studied, too. A non-linear three-dimensional finite element analysis is also carried out to study more exactly the behaviour of the frame and to check the validity of the simple analytical formulas. In the last part of this report, the results of structural model tests are compared with those of the analytical study and the finite element analysis.