The Alzbrücke Seebruck bridge carries the state road 2095 over the Alz river, into which the Chiemsee flows in this area. The superstructure of the existing structure was severely damaged, necessitating the construction of a new bridge section. Geotechnical investigations confirmed that the existing foundation structures, dating from 1933, still had full load-bearing capacity. In the long term, it is planned to build a bypass and to convert the Alzbrücke into a pedestrian and bicycle bridge. Until then, the bridge must remain in full use as a road bridge.

The bridge was to be closed for a maximum of one construction season for the renewal of the structure. In order to continue using the substructure, additional loads or settlement of the foundation elements must be eliminated. To absorb the loads from the bridge deck, the pier heads were reinforced with prefabricated steel structures. The bearing benches of the two abutments were also reinforced to absorb the loads from the superstructure. Due to the increased traffic loads, it was necessary to minimize the weight of the partial new construction. For the renewal of the superstructure, a lightweight steel composite structure with a high degree of prefabrication was chosen. The standard cross-section consists of four prefabricated composite girders with cast-in-place additions. To further reduce weight, the precast slabs and caps were made of lightweight concrete.

The preservation of the substructures and their foundations, which were more than 90 years old, contributed to sustainable construction. Non-destructive testing methods were used to verify the perfect condition of the existing components. Continued use was ensured by consistently minimizing the weight of the new superstructure. Interventions in the sensitive ecosystem of the Alz were thus kept to a minimum.