Crane Ship Response to Wave Groups

Abstract

The motion response of a shear-leg crane ship lifting a heavy load in wave groups was investigated. The 9-DOF dynamic model incorporated hull motions coupled with nonlinear large-angle load swing and elastic stretch of the hoisting rope assembly. Hydrodynamic response forces and wave excitation forces were taken to be frequency dependent, and nonlinear mooring system restoring forces were allowed for. Closed-form linearized results about the system equilibrium state verified our nonlinear simulation algorithm; simulation results in comparison with scale model test measurements, our mathematical model. Wave groups were idealized in two different ways: 1) as continuous wave groups produced by pairs of beating waves of equal amplitude and slightly different periods, and 2) as isolated wave packets generated by superimposing a large number of regular wave components derived from a Gauss-modulated amplitude spectrum. Simulations show that hook load response, strongly coupled with ship motions, was mainly influenced by first-order wave-exciting forces. Low-frequency horizontal ship motions caused by second-order wave (drift) forces did not generally affect hook load response, i.e., first-order and second-order responses were independent.

Nonlinear hydrodynamic responses of submerged moving payload in vicinity of a crane barge in waves

“…A similar problem has also been investigated by Schellin et al in a later study [14], where using idealized wave groups they have shown that hook load response, when strongly coupled with ship motions, is mainly influenced by first-order wave-exciting forces. Jiang and Schellin [15] have developed another model to study the influence of nonlinearities arising from the mooring system and fluid viscosity.…”

Determination of Reaction Forces of a Deck Crane in Wave Motion Using Screw Theory

“…The dynamic coupling between crane load and vessel motion was studied in Ref. [1] for a floating crane barge. The response of the barge was found when the barge and the crane are modeled as one rigid body.…”

Dynamic Analysis of Topside Module in Lifting Installation Phase

“…The hook load consists of the weight of the deck structure, the weight of the rigging, external wind forces and dynamic loads caused by the dynamic motions of the crane vessel and transportation barge (Choo, et al 1993). The loads experienced by the transportation barge are wave-induced loads, the loss of structure weight by the lifting, and an impact load if the vertical motion of the barge relative to the deck structure is greater than the transient air gap between them (Cveticanin, 1995;Schellin, et al 1993).…”