Of course, this small bridge is not the bridge over the A 8 near Holzkirchen, which is currently being rebuilt with some effort. It is also not one of the half-dozen bridges that have to be renovated on the A 92 alone between Moosburg and Landshut, and it is certainly not the motorway bridge near Lüdenscheid, which was closed quite unexpectedly last December and is to be blown up in early 2023. On the contrary: this small bridge near Wörth in the municipality of Schwindegg should be finished by the end of December. And it should not only lead across the Isen river, but in the long term also mean that many other bridges in the state will not eventually get as far as the one in Lüdenscheid.
For this reason, Johannes Wimmer is back in Wörth that day. The young man with the safety shoes, suitably dirty work trousers and a firm handshake has been working on this bridge since construction began in May, and at the same time he is working on his doctoral thesis at the University of the Federal Armed Forces in Munich. When he unwinds one of his thick cables with the many thin wires in them on the construction site, the workers are no longer surprised. The prefabricated concrete parts they used here have recesses and cable passages that are not found on other bridges.
Johannes Wimmer will install around 150 sensors on the bridge, which has a span of 23 meters and a roadway width of 6.50 meters including the footpath and cycle path. They will continuously record pressure, strain, inclination, vibration and temperature in the structure. In addition, there are weather data such as wind, rain, solar radiation and air temperature as well as the water level at the Isen water gauge, which is right next door. Such factors constantly act on bridges. Of course, there have long been “some detailed studies,” says Johannes Wimmer. But a whole bridge full of sensors that measure practically all influences around the clock, according to Johannes Wimmer and his boss and doctoral supervisor at the university, that is at least “unique in Europe”.
The same bridge will even be created a second time by Professor Thomas Braml at the Institute for Structural Engineering in Neubiberg – as a “digital twin” on the computer. Such virtual doubles have long been commonplace in industrial plants, but the technology has only gained importance in construction for a few years. The twin is much more than a digital design model, which does not even exist in the case of the new Isenbrücke. Europe’s first “digital bridge” will be connected to all the sensors in the real bridge via mobile radio and will thus be exposed to the same influences practically live on the computer as the original, which spans the Isen in Wörth.
Johannes Wimmer keeps a close eye on the new bridge – in future also from the computer at the university.
(Photo: Matthias Köpf)
That such an opportunity arose in Wörth is a stroke of luck for Wimmer and Braml. Johannes Wimmer actually asked a fire brigade colleague at the festival at home in Gangkofen if he knew of a used bridge that could be brought to the campus in Neubiberg for experiments. That fire brigade colleague is responsible for the construction department in the Mühldorf district office, among other things, and immediately thought of the dilapidated bridge in Wörth that the district had to replace. At some point, both at the beer table thought a little further: Why not attach the sensors to the new bridge right away?
The district office did not have to be persuaded for long: one less bridge that Robert Martinez will have to take care of in the future. He is currently in charge of the new building for the office, which, apart from all the sensors, is actually not a difficult project. It costs the district 2.1 million euros, almost a million of which is paid by the Free State. The research project is entirely at the expense of the university and the “Center for Digitization and Technology Research of the Bundeswehr” and its project “risk.twin – Intelligent Critical Technical Infrastructure”.
Sensors in the concrete of the bridge will continuously provide data on the condition of the structure.
(Photo: Matthias Köpf)
Because a bridge is also that: critical infrastructure, and therefore in case of doubt a case for national defense. According to Thomas Braml, the primary research goal is civil, namely “intelligent life cycle management”. He and Wimmer want to correlate all their live data on the condition of the bridge and the various influences. In the best-case scenario, the computer on this bridge, and eventually on many others in the country itself, will draw its own conclusions from the data and point out in good time that something needs to be done here or there soon, long before the next inspection reveals serious damage and a major renovation is due or a demolition as in Lüdenscheid. The whole thing is designed for a much longer time than just a doctoral thesis, says Johannes Wimmer. The new bridge in Wörth would probably last a few decades.