Accurate and up-to-date evaluation of extreme load effects for bridge assessment

In the 1990‟s, during the background works of Eurocode 1991-2 (Traffic loads on bridges), extreme loads and extreme load effects have been evaluated by using WIM data recorded at various European locations. The most used WIM data file is a WIM data record, 2-week long, recorded at Auxerre on a French heavy trafficked motorway in 1986. Today, WIM records are longer and much more accurate, thanks to the fast progresses of the WIM technology. Thus they give a better account of the traffic variations along time. After the action COST323, self-calibration of WIM system has been generalized and the sensor and software technologies were improved. Therefore, uncertainties in the calculation of traffic effects on bridges are lesser than 25 years ago. To up-date the maximum load effects calculated in the late 1980‟s and used for the calibration of the load model LM1 of the Eurocode 1991-2, using the most recent WIM data, but also advanced extrapolation methods, extrapolations are made using various methods (Gaussian fitting, Gumbel fitting, Rice formula, Generalized Extreme Value, ..). Confidence intervals on the extremes that are found are derived. Among the several extrapolations methods found in the literature, a choice was made according to the objectives and the chosen methods were applied to traffic loads and traffic load effects. Results are discussed with respect to the method robustness vs the traffic data, the period of extrapolation and the load effect considered, as well of the likelihood of the final results.