Motion of Freely Suspended Loads Due to Horizontal Ship Motion in Random Head Seas.

A theory is developed for the swinging motion induced in a wire suspended load due to the horizontal motion of a ship. An explicit formula is obtained for the significant amplitude of horizontal load motion when the ship is exposed to random head seas. Numerical results are presented for two typical cargo ships in a sea state three. It is found that very large motions are suffered by the load. For critical line lengths, resonance effects magnify the ship motion by several orders of magnitude. These results will be used to assist in the development on-loading and off-loading devices for cargo vessels in open beach operations.