Development of structural reliability analysis methodology for prismatic pressure vessel with internal lattice structure

Abstract

In this study, we propose a prismatic pressure vessel with internal lattice structure capable of storing high pressure and high-volume fluids with high volumetric efficiency. And structural reliability of the proposed pressure tank is determined using the structural reliability method, which is a stochastic analysis method. A prismatic pressure vessel has a rectangular cross section, unlike generally used cylinder or sphere pressure vessels, and have an internal lattice structure that can withstand the load. First, to verify the technical feasibility of the proposed prismatic pressure vessel with internal lattice structure, the prototype tank was designed, fabricated and hydrostatic pressure test according to ASME code. The design was conducted by DBA (design by analysis) method, and the linear elastic and nonlinear inelastic behaviors were investigated based on the materials. Hydrostatic pressure tests measured the amount of deformation in the prototype tank using a strain gauge and compared it with the FEM analysis. Through this experiment, it was confirmed that the prismatic pressure vessel with internal lattice structure can store fluid at high pressure and high volumetric efficiency, and can be technically manufactured. Second, based on the technical feasibility of prototype tanks, the possibility of tank enlargement and the use of fuel tanks in LNG propulsion vessels was analyzed. Through the analysis of ASME, IGC and IGF codes, a prismatic pressure vessel with internal lattice structure was designed according to the novel shape pressure vessel design procedure. A case study was conducted on LNG-fueled tankers. Design feasibility analysis was performed through strength analysis at design pressure and hydrostatic test pressure, and ultimate load, dynamic acceleration analysis, buckling and thermal deformation, and fatigue analysis were also performed. These analyzes confirmed the possibility of large-scale prismatic pressure vessel with internal lattice structure and the storage of high-pressure LNG in LNG-fueled vessels. Lastly, for more reliable design and analysis, we propose a time-dependent structural reliability analysis method that can be used in a prismatic pressure vessel with internal lattice structure. In the past, the design and analysis for pressure vessel were carried out using a deterministic method, and safety was checked using the safety factor, which is the ratio of the allowable stress of the material to the stress of the structure. However, the safety factor did not give information on the effect of each design variable on the safety, and when one variable with uncertainty was used as a representative value, the maximum load was overlooked. As a result, many structural reliability techniques have been used, in which design variables are used as random variables and structures are represented as limit state functions composed of random variables. In this study, the time-dependent method of structural reliability was used as an evaluation technique in the design of a prismatic pressure vessel with internal lattice structure.