Fatigue life prediction of RTG steel structures based on FEA and stress online monitoring

Fatigue is one of the primary factors responsible for the failure of the steel structure of the rubber tire container gantry crane (RTG). A fatigue life prediction method was proposed based on the working conditions and dynamic properties of RTG. Firstly, finite element analysis (FEA) was adopted to compute stress of gravity, and the entire stress spectrum sample was approached through linear superposition with external load stress obtained from stress online monitoring. Then, rainflow counting method was employed to obtain S-N curve, and time-domain fatigue life prediction was performed based on Miner rules fatigue. Next, the stress spectrum samples were converted into frequency domain signals through the Welch function for fast Fourier transform, and then the fatigue life prediction in frequency domain was conducted based on Dirlik and ZB models. The analysis revealed that the relative errors associated with the three models were minimal. The time-domain approach necessitated the utilization of an extensive array of stress spectrum samples, whereas the frequency-domain technique offered a more computationally efficient alternative. The three models holds significant promise for widespread application in engineering practice.