Statistical Extrapolation for Extreme Traffic Load Effect Estimation on Bridges

This paper presents a comparison of two methods of statistical extrapolation, the method of block maxima with fit of generalised extreme value distribution, and the level cross counting method with fit of Rice’s formula, applied for estimation of extreme traffic load effects on road bridges. For the purpose of this investigation, both real traffic streams from actually recorded traffic data and synthetic traffic streams generated by means of traffic simulation based on probabilistic descriptors for the essential traffic parameters are analysed. These traffic streams are then applied to a selected bridge structure performing structural analysis, to obtain load effect time histories of a certain structural response parameter due to this traffic loading. These time histories constitute the base for subsequent extreme load effect estimation using the different methods of statistical extrapolation. The methods, their main assumptions and limitations are shortly reviewed. Numerical results from their application are presented in detail and compared to each other. Sets of different traffic stream lengths and extrapolation ranges (desired return periods of extreme load effects) are analysed to investigate their effect on uncertainties and convergence behaviour. Based on this comparison, the appropriateness of application of the methods is discussed.