Non Linear Effect on Wave-Induced Loads for Hull Structural Design: Bulk Carrier, Container Carrier, Vehicles Carrier

Abstract

Abstract The structural rules of classification societies typically specify various loads corresponding to the most severe sea states which are expected to be encountered by a ship throughout her service life in order to ensure ship structural safety, and these rules also usually define a variety of simplified formulae to aid in the calculation of such loads. In most cases, such formulae have been developed using linear seakeeping codes and linear statistical predictions; such methods, however, do not typically take into account some complex phenomena due to theoretical and methodological limitations. For this reason, the use of values obtained through linear theory alone is often not sufficient to properly evaluate structural strength, and it is, therefore, necessary to consider other things such as non-linear effects and operational effects. Although the structural rules of classification societies normally take into account such effects, most of them generally treat such things simply as either a constant coefficient or as an implicit condition because of the difficulty of expressing such effects mathematically (i.e. as specific formulae) as well as a general lack of prior research related to such effects. In this paper, the authors present the results of tank tests and numerical calculations carried out in regular and irregular waves using a bulk carrier, a container carrier and a vehicles carrier, and discuss possible ways of improving the non-linear coefficients specified in the IACS Common Structural Rules (CSR) [1]. Load states, including their non-linear effects, were investigated by examining the behavior of ship motions and hydrodynamic pressure. In order to investigate the behavior of pressure in detail, the pressure acting upon the hull surfaces of the target ships was measured at over 300 locations using a FBG sensor, the latest in optical fiber sensor technology [2].