The load-bearing capacity of cylindrical shells of a composite fiber material that are at risk of buckling is determined by deriving improved reduction factors for analytical calculation of the design load. A load distribution head applies an axially acting force to a cylinder shell. A dent actuator dents the surface of the cylinder shell in a predetermined dent direction with a predetermined dent depth. A dent force is determined when a steadily increasing, axially acting force is applied to the cylinder shell by the load distribution head until a complete failure of the cylinder shell is detected. An analysis unit determines a dent depth from a data memory at which a dent force at a complete failure of the cylinder shell is at a maximum compared to dent forces of other dent depths.