Risk to historical bridges due to ship impact on German inland waterways

We describe the investigation of two old bridges over inland waterways in Germany under a possible ship impact. Both the numbers of ship impacts against bridges in Germany and the structural description of the bridges have been studied. The investigation is based on probabilistic calculations to take into consideration the uncertainty of a possible impact and the uncertainty of material parameters of the historical bridges. The results for the original bridges and additional strengthening measures are presented in terms of probability of failure and also in terms of risk.