THE MOTIONS OF A MOORED CONSTRUCTION-TYPE BARGE IN IRREGULAR WAVES AND THEIR INFLUENCE ON CONSTRUCTION OPERATION

Results and methods are given for a theoretical study of the behavior of a moored construction type barge and that of a load, lowered by means of a line from the barge, in irregular seas in deep water. The mooring system considered is a conventional line-and-anchor type, with both bow and stern moorings. Load-lowering through the hull as well as by means of a boom having variable azimuth angle is considered. Equations of motion of the system for sinusoidal waves of arbitrary length and direction are formulated for six degrees of freedom, and take into account both hydrostatic and hydrodynamic effects. Following the evaluation of the excitation functions and the coefficients in the equations (based on the particular barge under study), sinusoidal solutions of these equations are obtained for each of the six barge motions (surge, heave, pitch, sway, roll, and yaw), as well as for the three rectangular components of the load displacement vector, the vertical component of the load acceleration and the added dynamic tension in the lowering line. In addition, solutions are obtained for the forces in the mooring cables and the horizontal components of the force and the yawing moment induced by the mooring system on the barge.