DESIGN PROBLEMS AND OPERATIONAL RISKS OF CRANE VESSELS

Operational aspects of crane vessels at sea are identified by examining the following three motion categories: harmonic motions occurring in the smaller natural periods of the non-elastic system; transient motions occurring in the larger natural periods of the non-elastic system; and transient motions occuring in the relatively small natural periods of the elastic system. Operational problems associated with the first category can generally be avoided by setting operating limits and those in the second category by extensive theoretical evaluation. Structural loadings which may reach critical levels during operating conditions are described in the third category.