General restoration of the Ludwig Bridges in Munich
|Company||PORR GmbH & Co. KGaA|
|Principal||Landeshauptstadt München – Building Division, Department of Civil Engineering|
|Location||Munich - Germany|
|Runtime||06.2020 - 10.2022|
PORR renovates structures on historic Isar river crossing
It was a particular honour to carry out the structural strengthening and general restoration of the bridge construction, as well as the footpaths and cycle routes underneath the bridge, because the Ludwig Bridges in Munich are one of the most important historic sites in Bavaria’s provincial capital. The first bridge over the Isar was erected here in the 12th century, leading to Munich’s rise as a significant trading centre.
The Department of Civil Engineering, representing the Buildings Division of Landeshauptstadt München, was thoroughly satisfied with both the quality of the work and the adherence to schedule of the PORR team, which was made up of members from Germany and Austria. PORR Hochbau Oberösterreich and PORR Tiefbau Tirol supported the main contractor ZNL Saaldorf-Surheim by carrying out concrete renovation and asphalting works.
Expertise and sensitivity required
The inner and outer parts of the Ludwig Bridges are separated by Museum Island. The steel and concrete arched bridges, built in 1934 and 1935, are arranged in series and clad in natural stone. Reports of damage were becoming more frequent during regular construction inspections, which is why it was necessary to carry out general renovation work to ensure the bridge would be remain useable for decades to come.
In phase 1 the cross reinforcement on the underside of the outer part of the Ludwig Bridges were strengthened piece by piece in a pilgering process. Working just a few metres from the often flooded Isar was a particular challenge.
The second phase of construction followed, with cross reinforcement of the vaulted ceilings of the footpath underpasses, and restoration or renovation of the road slabs. The existing structure had to be cut away, removed and rebuilt piece by piece in order to ensure the bridges remained structurally stable at all times.
The third phase of construction revolved entirely around strengthening the crown hinges. Extensive tests carried out during the construction work confirmed that the hinges were structurally sound. This meant that the complete renovation of the hinges originally planned, an extensive and technical undertaking, was not necessary. The only work necessary to reinforce the hinges was a minimally invasive procedure to strengthen the tensile gap reinforcement using innovative concrete screws.
The reconstruction measures on the Ludwig bridges were carried out while road traffic continued to flow.© PORR