After three years of monitoring the Kreuzhof bridges in Munich, destructive structural tests were carried out on two bridges shortly before their partial demolition. By cutting through a large number of tendons, artificial wire breaks were produced on the tendons with prestressing steel at risk of stress corrosion cracking. The aim of the tests is to investigate the effects of prestressing steel fractures and to validate the existing monitoring systems. In collaboration with the engineering company Büchting+Streit AG and the acoustic sensor manufacturer iNDTact, the existing monitoring system was tested using acoustic emission analysis and fibre optic sensors (DFOS). This involved the use of 68 AE sensors and approximately 1100m of fibre optic sensors. The Chair of Concrete and Masonry Structures coordinated the tests on behalf of Buechting + Streit AG and has been responsible for the fibre optic sensors since the start of the monitoring.
The monitoring was initiated in 2021 after a comprehensive concept by Büchting+Streit AG. Since then, the condition of the Kreuzhof bridges has been monitored. The City of Munich decided some time ago to replace the bridges due to the risk of stress corrosion cracking in the prestressing steel and the fact that the future tram west tangent will pass under these bridges.Two of the three substructures have now been dismantled.The sensors on the remaining substructure will remain in place until it is dismantled in order to continue monitoring potential structural changes.
We would like to thank the City of Munich for their confidence and the rare opportunity to carry out such valuable research. We would also like to thank all those involved for their excellent cooperation.