A Route Or Mission-Dependent Approach For The Calculation Of Rational Structural Dynamic Loads For High-Speed Multihulls

摘要

A two-phased integrated methodology to predict the route/mission-dependent rational structural dynamic loads for high-speed multihulls was developed. The project was funded by the Center for the Commercial Deployment of Transportation Technologies (CCDoTT). The specific program of work described in this paper represents the first phase of the two-phased effort to develop a ship motion and dynamic load calculation methodology that would be suitable for use by Designers, Classification Societies and the U.S. Navy. The method developed would be suitable for advanced hullforms, including slender monohulls, catamarans and trimarans, SES, and other advanced hullforms. In Phase I, an overall working model of a frequency-domain ship motion and loads model was developed, incorporating a route-based mission profile module to provide a description of the ships' overall lifetime loads. A commercial ship motions program that can accommodate multihulls, titled SHIPMO, was utilized to model the motion characteristics of advanced hullforms, including catamarans and trimarans. The results of the numerical predictions were compared with model and full-scale data, and analytical rationales were developed for the differences between the experimental and predicted data. Subsequently, modifications to the numerical modeling procedures were applied to overcome any such limitations to the greatest extent possible within the bounds of the Phase I effort, allowing the utilization of SHIPMO to compute short-term frequency-domain vessel motion and load statistics. A comparison of existing extreme value estimation methods was developed, in addition to a methodology to estimate extreme loads from the calculated frequency-domain statistics. Thereupon, a procedure and rationale was developed for determining the load for a probability-based structural design method. Phase I validation efforts were conducted using a notional east coast AutoFerry concept that was previously developed by the authors. This paper summarizes the contributions to the state-of-the-art on rational structural design methodology accomplished during Phase I of the project.