A first principle approach for the strength analysis of a semi-swath vessel

Abstract

Structural strength is an important factor for a Semi-Small Water-plane Area Twin Hull (Semi-SWATH). A Semi-SWATH ship is a combination of the Small Water-plane Area Twin Hull (SWATH) ship in the forward half and conventional catamaran in the stern half. Due to the twin hull design, strength analysis is most important, especially in transverse direction to prevent structural failure in the cross deck between two hulls. In this research, a First Principle approach using modified formula for strength analysis of a semi-SWATH structure was developed. The approach focussed on evaluations of the longitudinal and transverse strengths of the Semi-SWATH bulkhead. Predictions using this First Principle approach are mostly catered for failures and high stress concentrations especially at the transverse structures that connect the twin hulls. To verify the results, a 1:10th scale model of the Semi-SWATH was tested in the National Hydraulic Research Institute of Malaysia (NAHRIM) tank facilities. Data Acquisition System (DAS) was also developed to capture the strength data of semi-SWATH vessel structure by using strain gauges. Data collected from DAS were customized by using LabView software through SCXI signal conditioning. The experiment results were used to verify the results of static and wave impact in head seas on the compartment’s beam structures. It was found for the case of plating failure, the First Principle approach predicted stress values of 52.6% and 15.34% higher as compared to experiment and Finite Element Method (FEM) respectively. The results are significant on ship structure analysis as reported by Ship Structure Committee SSC, which was in the range of capacity design value of the bulkhead compartment structure.