Abstract: Abstract： 【 Objective 】 To improve the efficiency and effectiveness of searching the worst position of wheel patch loads on deck grillage 【 Method 】 In this paper, the worst-case analysis of deck girder under wheel patch loads is regarded as a constraint optimization problem, and a method combining the domain knowledge of ship structure mechanics and simplified model for the analysis of worst-case of deck girder structure under wheel patch loads is proposed. According to the specified girder to be analyzed, the method firstly applies concentrated forces to different positions on the corresponding girder of the deck grillage in advance, and selects several suitable girders according to the response value to form a simplified intersecting beam system model, and carries out the analysis of the worst-case with genetic algorithm together with domain knowledge. Then, keeping the order positions of the loads in the worst-case on the simplified model unchanged, and the loads are applied to the girders of the deck grillage with similar modes to the simplified model or the specified girder of the deck grillage to traverse or perturb, and finally the positions of the dangerous wheel patch loads on the specified girder of the deck grillage is obtained.【 Results 】 The worst-case of the girder under different number of wheel patch loads and different minimum load spacings were calculated by using three methods: direct searching method for the deck grillage, direct searching method for deck grillage with domain knowledge and the method of the combined domain knowledge and simplified model. The numerical results show that compared with the direct searching method without any strategy, the maximum bending normal stress and shear stress of deck girder obtained by the proposed method can be increased by 15.9% and 30% respectively. The computational resources are only about 1/32 of that obtained by the direct searching method and 1/8 of that obtained by the direct searching method with domain knowledge. Moreover, the difference between the results of multiple solutions obtained by the proposed method is small.【 Conclusion 】 The proposed method can quickly and effectively and robustly search the dangerous load positions of deck girder under multiple wheel patch loads.