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Structural analysis does not consider weld seam. Research on welding seldom pays attention to structural strength analysis. The working conditions of super large structure are complex, and the design requirements are very high. The coupled relationship between the structure of weld toe and frame stiffness in actual working conditions is analyzed to improve the accuracy of finite element model. Using the finite element method as basis, this study establishes the finite element model for the frame. The fillet joint models for the different forms of weld toe are established on the basis of thermo-elastic/plastic theory. Weld toe optimization scheme is applied to analyze frame strength. The accuracy of the model is verified by experiments. Results show that high stress appears at the connection position of the left-right longitudinal beam and rear torsion tube and the middle of rear torsion tube due to the interaction of torsion and braking. Stress between the frontal longitudinal beam and portal-type girder assembly does not significantly vary. The weld height and toe of the fillet joint are 20 mm, and the stress peak value is small. The stress distribution of the frame is analyzed by optimizing the weld toe. The stress peak value is reduced from 453.8 MPa to 340.6 MPa. Through the repair welding of the weld toe position for the optimization scheme, the welding seam surface forms a concave arc and reduces the stress concentration effectively. Failure time of the frame increases by no more than 5000 hours and does not exhibit fatigue failure. Research results are crucial for establishing coupled relationship with weld toe and frame strength and optimizing welding.

To explore the influence of mesh size on the accuracy of welding simulation, the weld seam and heat affected zone are treated with different mesh sizes. The finite element models are established to obtain the welding deformation and residual stress distribution of the lap joint. The results are verified by the test. The results show that, from the trend of deformation and residual stress distribution, results from different weld mesh sizes coincide with the distribution trend of test results, which proves the validity of the finite element models. Welding deformation of the starting arc position is less than that of the ending arc welding position, and the maximum deformation position occurs on the free side along the longitudinal end of weld seam. The change of mesh size has a certain effect on the residual stress distribution. By comparing with the test results, the errors of mesh size of 0.5mm, 1mm, 2mm and 3mm are 2.4%, 5.1%, 16.6% and 12% respectively. The research results have important guiding significance for the pre-processing of welding simulation.

For roll-over protective structures (ROPS) in a mechanical driving dump truck cab, it simulates the lateral, vertical and longitudinal loads of ROPS. It obtains stress and deformation of the cab that occurs to roll. For the relative weak position of ROPS in the cab, the structure of the cab is improved and verified according to the ISO 3164: 1995. The results show that the established finite element model can effectively predict the deformation and stress distribution of ROPS, and optimize the weak structure of the cab, which has important guiding significance for structural design of the cab and ROPS optimization of the mechanical driving dump truck cab.