Comparison of the collapse frequency and the probability of failure of bridges

In this paper, the collapse frequencies of bridges are summarised and compared with target values of probabilities of failure and with calculated failure probabilities for real bridges. The determination of the collapse frequencies is based on various publications in the sense of a meta-analysis. First, the various studies are summarised graphically, discussed and examined for a trend. The results show that the collapse frequencies decrease over time and that today they have reached a minimum. In the next step, the observed collapse frequencies, the target failure probabilities and the calculated failure probabilities are compared. There is a good agreement between the collapse frequencies and failure probabilities for real bridges. The collapse frequencies fulfil the current safety targets for time-dependent target probabilities as well as for time-independent target probabilities for dead and traffic loads. Subsequently, the causes of bridge collapses are assessed regarding loads. The main cause for bridge collapses is accidental loads, such as hydraulic events. Such loads can be controlled if they are considered in the correct order of magnitude. The probabilities of failure can be extended regarding further factors and thus the matching between probabilities and frequencies can be further improved.