On Safe Offshore Operation of Crane Barges

Abstract

For crane barges operating in the seaway the failure mode “eigenmotions” must be considered to be most important. Eigenmotions become excessive if the crane barge is excited by waves with periods equal to the natural periods of the barge. In a working condition, i.e. if the crane is lifting a load, the natural periods of the system depend on the weight of the load, on the length of the hoisting rope between the load and the boom point as well as on the hydrodynamics of the barge itself. Thus, the qualities of two crane barges can be compared only with respect to a specified task under given sea conditions: The barge with the lower probability (risk) of eigenmotions may then be considered more effective, i.e. it can be operated more safely and more economically than the other one. Therefore, to be able to understand such qualities of different designs for any specified purpose, it is of fundamental importance to determine the risk of eigenmotions of crane barges already in the design stage, i.e. theoretically.