Old bridges in new times. Searching for hidden quality

Many bridges in The Netherlands are meanwhile 40-50 years old. Those bridges have been designed according to old design codes, which do not reflect the state of the art of today anymore. Moreover, the traffic loads have been increased substantially. If those bridges are recalculated according to modern design codes they often do not fulfill the safety standards. In spite of that, those bridges mostly do not show significant distress, which denies the results of the analysis. Obviously there are hidden reserves in bearing capacity. To detect and quantify these is an important task.