A pilot project at Munich's Olympic Stadium demonstrates how safety-relevant screw connections in steel construction can be monitored digitally. Here, existing screw connections on the visitor platform integrated into the roof were supplemented with fischer SensorBolts. These intelligent, high-strength screws feature integrated force measurement and transmission technology to measure their preload forces in real-time, thus enabling greater transparency and safety in building operation.

The Munich Olympic Stadium is unique in terms of steel construction – not least because of its filigree tent roof, which was honoured with the title "Historic Landmark of Engineering in Germany" on 22 September 2023. With an area of around 78,000 m², it covers almost half of the stadium as well as the adjacent halls (Olympic Hall and Swimming Hall) and intermediate roofs. At a height of around 40 to 50 m above the playing field, secured walkways lead across the roof structure, which are directly integrated into the filigree steel cable construction. On a "tent roof tour", visitors equipped with climbing gear can walk on the iconic tent roof – with a view over Munich, down onto the playing field, and, on a clear day, all the way to the Alps. All connections on the visitor platform must be absolutely reliable, additional safety requirements arise from the "Flying Fox": a 200-metre-long zip line that runs across the stadium lawn at a height of around 35 metres and, if desired, forms the conclusion of the tour.

High-strength connections digitally monitored
Munich's municipal utilities have now successfully supplemented the screw connections on the visitor platform of the Olympic Stadium with fischer SensorBolts. These sensor-integrated bolts meet the safety requirements for heavily frequented and safety-relevant areas. Attached directly to the screw head, a sensor measures the preload force – the decisive factor in steel construction for indicating how tightly components are clamped together with the screw. A second sensor records the temperature, thus also taking environmental influences into account. Each SensorBolt is equipped with a SensorNode, which securely transmits the measured values – in kilonewtons (kN) – from the bolts to a gateway installed in the stadium. From there, the data is sent to cloud storage with end-to-end encryption and made accessible via a customer-specific dashboard. This allows stadium operators to conveniently view the condition of the fastening points at any time and from any location via PC or smartphone – in real-time.

The next level of intelligent screw technology in view
"With our SensorBolts, we are taking intelligent screw technology to the next level," emphasises Dr Daniel Rill, Product Manager for Connected Products at fischer. Until now, it has been very costly to determine the preload forces of installed screws in classic building operations – especially over longer periods of time and under changing loads. "Our sensor innovation now makes it possible to continuously monitor the screw connections remotely and collect precise, real-time data on their condition – including information on how forces change over time due to wind, temperature or snow loads, for example," Dr Daniel Rill continues. "The result is a significant increase in operational safety and controllability – especially in safety-critical areas such as the visitor platform of the Olympic Stadium in Munich." Safe and economical building operation is a clear advantage here. Dr Daniel Rill emphasises: "The integration of our SensorBolts into safety concepts allows for more targeted planning of maintenance measures. This reduces downtime and lowers costs – while further optimising the already very high safety standards of the visitor platform and extending its service life even further."

Structural health monitoring is advancing
"Our SensorBolts make screw connections smarter, more future-proof and absolutely reliable – a milestone for the safe, sustainable and economical monitoring and maintenance of buildings and facilities," summarises Martin Neumann, Head of Connected Products at the fischer Group. The SensorBolt is the latest addition to the fischer Construction Monitoring portfolio of digitally equipped fasteners, which also includes the SensorAnchor anchor rod and the SensorDisc washer. All three IoT-connected products enable the documentation and monitoring of structures and facilities. The condition of fastening points can be viewed in real-time via smartphone or PC – even remotely. "This improves maintenance efficiency, enables cost savings, increases safety, reduces downtime and extends the service life of the objects," emphasises Martin Neumann. The first pilot projects are running very successfully – further fields of application are in the planning stage.