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.

The transverse stress of the bottom grillage becomes a rising concern with the increase of the width of the super large container ships. It analyzes the stress response of the bottom grillage in the cargo tank region of a container ship by considering the various asymmetric transverse load types, load conditions and dynamic load conditions based on the numerical simulation of the cabin. It also discusses the influence of the asymmetric transverse load types on the distribution of the local strength and the stress of the bottom grillage, and the influence of the different dynamic load conditions on the bottom grillage under the asymmetric transverse load. The results show that the distribution of the high stress points under the asymmetric transverse load is similar and the stress level of the asymmetric transverse load is higher than that of the original symmetric load. The influence of the possible asymmetric transverse load types is recommended to be considered in the check of the strength of the container ships.

It focuses on the assessment of the overall strength of container ships. The basic theory of the method is to determine the local loads based on a single Equivalent Design Wave(EDW), and adjust the hull girder loads to reach the envelope values of multiple EDWs, in order to represent the calculation results of multiple EDWs at one time. It is proved that the most dangerous load case in the multiple EDWs, which may be omitted by traditional rules, able to be covered by this method. The calculation workload is able to be greatly reduced because there is no need for a large number of design wave calculations. It is applicable to the strength check and the determination of the structural design scheme in the early design stage.