Rigid Body Ship Responses and Associated Periods for a Series of Liquid Natural Gas (LNG) Ships.

摘要

The purpose of this report is to develop the RMS ship responses required to determine LNG tank design (extreme) acceleration rules. The actual design rule work is presented in a separate paper. The Root mean square (RMS) data base presented is for a series of five LNG ships ranging in length from approximately 600 to 1000 feet and with capacities ranging from 29,000 to 200,000 cubic meters. Ships with both spherical and membrane tanks are included. The data base consists of six rigid body ship responses, i.e., heave, pitch and roll along with longitudinal, lateral and vertical accelerations at the center of the forward tank for each of nine ship/load cases. Periods associated with each response are also given. The data base covers a wide range of ship speeds, i.e., 0,5. . ., 20 knots, ship headings, i.e., 0, 15, . . ., 180 degrees and modal wave periods, i.e., 7, 9, ..., 21 seconds. The seaways are presented by short crested Bretchneider two-parameter spectra with one foot significant wave heights, so that the data can easily be scaled to any wave height. The effect of load variations is evaluated by determining ship responses when GM is varied.