AN EXACT SOLUTION FOR A SIMPLIFIED MODEL OF THE HEAVE AND PITCH MOTIONS OF A SHIP HULL DUE TO A MOVING LOAD AND A COMPARISON WITH SOME EXPERIMENTAL RESULTS

The coupled heave and pitch motions of a simplified non-uniform ship h ull floating on a still water surface and subjected to a moving load h ave been investigated. The ship hull was considered to be a rigid body supported by an elastic foundation with distributed springs and dampe rs. Based on the general equations of ship motions in waves, the gover ning equations of the ship hull were derived. For the case of a consta nt moving load speed, a closed form ''exact solution'' was obtained. F or the purpose of comparison and more general studies, a numerical app roach was also introduced. The influences on the dynamic responses of ship hull of some factors such as the moving load speed, direction of movement, landing position, initial velocity and acceleration, were st udied. To check the reliability of the numerical results, a simple mod el test was conducted and approximate agreement was obtained. The reas ons for the discrepancies between the experiments and theory are discu ssed. For simplicity, the damping effects due to ship-motion-induced w aves are replaced by the damping ratios in this study. (C) 1996 Academ ic Press Limited