About 25 years ago, the first concrete bridges were built in Germany, whose stressing components were no longer embedded in the concrete, but freely accessible. Meanwhile, such prestressed concrecte bridges with external pre-stressing are common practice in the Federal Republic of Germany and, hence, have gained importance in the construction of federal highways. For routine inspections, efficient and reliable measurement methods for the identification of damage are required. Conventional inspection methods, however, are very time-consuming and associated with high costs, such that they are used in exceptional cases only.An invention made by the Institute of Concrete Structures and Building Materials (IMB) allows for a rapid test to control external stressing components. The test is based on the fact that the frequencies of all stressing components in a bridge can be adapted to each other mathematically. In the repeated measurements, those stressing components are filtered out automatically, whose state has changed irregularly in the meantime. The signals are evaluated such that the result is available directly after onsite measurement. With this system, the inspection of all stressing components of a prestressed concrete bridge of about 200 m length will be accomplished within a single day in the future. Using conventional methods, measurement and evaluation today take about one month. The new invention reduces the inspection duration as well as the costs by a factor of 20. The system can be applied universally and is also suited for the inspection of cable-state bridges. In cooperation with an industry partner, the IMB is presently developing a mobile test instrument and a database system for the better processing of the test data measured.