Dynamic loading of shipboard cranes

Cranes, placed on board ships, experience dynamic loadings which generally do not exist for land based cranes. Equations of motion are derived for a simple model of a mass suspended by cable from a crane attached to a ship which has arbitrary prescribed motion. The response of the mass is determined, through numerical integration of the differential equations of motion, for a typical ship motion and for a range of cable lengths and rates of change of cable length. Large response angles of oscillation are seen to develop for certain critical lengths of cable. Reduction of response motion appears to be made possible through careful control of mass deployment or retrieval velocities.