Sensitivity analysis and optimization of design parameters were carried out for the key region of hopper knuckle connections in a very large crude carrier (VLCC), aiming to seek the optimal layout of hopper knuckle structures that meets the requirements of the common structural rules. A workflow for yield and fatigue assessment at hopper knuckle connections was first established. The effects of hopper knuckle plate angle, arc radius at the knuckle, and plate thickness on the stress level and fatigue life at the knuckle were studied using Latin hypercube design and orthogonal arrays. On this basis, an intelligent optimization algorithm was adopted to optimize the rounded lower knuckle connection, and the optimal design scheme was obtained. The sensitivity analysis results show that for the rounded lower knuckle connection, the thickness of the inner bottom plate is the most critical factor affecting the stress level, and the arc radius is the most critical factor affecting the fatigue life. The above analysis approach and optimization strategy can provide an empirical reference for the structural optimization design of hopper knuckle connections in similar vessels.

Lightweight technology is an important development trend of ships. Lightweight hull structure design may lead to novel designs that break through existing standards, including new structures or new materials. Based on an overview of the existing safety assessment system for ship structures, it focuses on the safety assessment process and methods for the lightweight structural design, including alternative design process, novelty evaluation indicators and approaches, and methods for determining structural safety assessment criteria based on limit states. The proposed novelty evaluation and safety assessment methods for the lightweight structural design are then applied for practical analysis of the typical cases of the lightweight structural design for oil tankers, bulk carriers, and container ships from literatures published at home. The proposed novelty evaluation and safety assessment methods for lightweight structural design can provide approaches and methods for the structural safety assessment of the corresponding new or alternative designs.

Aluminum sandwich panels are primarily used on luxury cruise liners and speedboats. The lightweight alterative design for the local structure of the superstructure of a common civilian ship is carried out to expand the application scope of aluminum sandwich panels. The structural configuration and the corresponding type of the connection structure are then determined according to the structural characteristics of the sandwich panel. And the mechanical properties of the superstructure before and after the alternative design are compared and analyzed by using the finite element software ABAQUS. The results show that the superstructure of aluminum sandwich panel have better mechanical properties with the reduced structure weight. It can provide reference for the promotion and application of aluminum sandwich panels in the future.