Objective This paper proposes a method for improving the efficiency and accuracy of finding the worst-case positions of wheel patch loads on deck grillage.

Method The proposed method combines the domain knowledge of ship structural mechanics with the simplified model. According to the specified girder to be analyzed, the method first applies concentrated forces to different positions on the corresponding girder of the deck grillage in advance, then selects several suitable girders according to the response value to form a simplified intersecting beam system model. It then carries out the worst-case analysis using the genetic algorithm and domain knowledge. Keeping the order positions of worst-case loads in the simplified model unchanged, the loads are applied to deck grillage girders with similar modes to the simplified model for traversal or perturbation, and finally the dangerous positions are obtained.

Results The worst-case positions are calculated using three methods: the direct search method for the deck grillage, direct search method for the deck grillage with domain knowledge, and combined domain knowledge and simplified model method. The numerical results show that compared with the direct search method without any strategy, the maximum bending normal stress and shear stress of the girder obtained by the proposed method can be increased by 16.1% and 26.9% respectively. The computational resources are only about 1/64 of that obtained by the direct search method and 1/8 of that obtained by the direct search method with domain knowledge. Moreover, the difference between the three-run results obtained by the proposed method is small.

Conclusion The proposed method can quickly, effectively, and robustly identify the dangerous load positions of a deck girder under multiple wheel patch loads.