Stochastic Service Life Prediction of Existing Steel Structure Loaded by Overhead Cranes

The article deals with the fatigue damage analysis of aging steel structures. The structure was built in 1920 and is used to operate an outdoor storage of steel rolled products. The structure serves as a support for overhead cranes with a lifting capacity of 8 tons. Reliability assessment including prediction of the residual service life was requested by the property owner. Corrosion state of structural elements and assessment of fatigue resistance represent the key data for the prediction of the residual service life. The study of the documentation and the inspection of structure was the first steps of the analysis. Next, the computational numerical model of the steel bar structure was prepared to identify the critical details for the fatigue assessment. The detailed numerical model of the selected structural part was used subsequently to check the fatigue resistance. In this article, special attention is paid to the calculation of load effects resulting from the operation of overhead cranes. A new innovative method based on the Monte-Carlo simulations and FEM model of the structure was used to determine the stress history. The following random variables enter the probabilistic analysis: (a) position of the crane bridge, (b) position of the crab, (c) payload, (d) number of crane travels during the evaluated period. Income information for the probabilistic analysis are taken from the technical documentation, skilled judgement of the operation technologist is used as well.