The design domain for the topological optimization of ship structures is usually based on two-dimensional shell elements. However, the thickness difference of the design domain affects the setting of volume fraction constraints and the acquisition of stable topological configuration, restricting the practical application of the topology optimization method in the field of hull structure design. Thus, relevant research needs to be carried out to solve this problem.

This paper takes the transverse web frame in the cargo tank of a very large crude oil carrier (VLCC) as the optimization object, and puts forward a compromise method for setting the volume fraction constraint value of the complex hull structure, as well as a method for determining the minimum stable topological plate thickness of the transverse web frame via element statistics.

Through theoretical analysis and trial calculation, it is found that the volume fraction value and minimum stable topological plate thickness can be obtained more reliably using this method.

The proposed method possesses validity and feasibility, and is able to provide technical support for the optimization design of the transverse web frames of large oil tankers. It can also provide references for the topology optimization of other complex hull structures.