Motorway A671 in Hessen crosses the Main river near Hochheim. On the northern side, the foreland bridges made of prestressed concrete connect to the three-span steel bridge over Main river. An expert report from 2015 documented massive damages at the bridge built in 1965 requiring a new structure. However, it could not be replaced until the end of its lifecycle in 2019 due to missing building permissions. To keep traffic going, all four main piles of the existing structure had to be reinforced by emergency supports.
To simplify assembly and demounting, steel scaffoldings form those emergency supports. They consist of singular supports in the span areas and at the existing pile axes. The supports are arranged at distances which allow the superstructure to distribute loads freely via the existing mild reinforcement after failure of the prestress. In the span areas, steel yokes support the bridge's three main girders on the east side. To strengthen the western bridge girder - necessary for the construction method of the replacement structure - individual supports are sufficient.
The construction method of the subsequently implemented replacement plans to separate the existing superstructure before construction start by a separating cut in longitudinal direction and to demolish the western girder. The eastern section of the superstructure will be pushed to the side after completion of the new superstructure west. The support scaffoldings at the bearing axes will thus be design from a technical and economic point of view so that they can be used for the ensuing transversal launching procedure.
Client: Hessen Mobil Road and Traffic Management
SSF's scope of services:
– Design of emergency scaffoldings as special proposal for transversal launching
– Project planning of engineering structures (§ 43) following emergency scaffolding: basic evaluation, preliminary, draft and final design, preparation and evaluation of tenders (Lph 1, 2, 3, 5, 6, 7) transversal launching: basic evaluation, preliminary and draft design (Lph 1 – 3)
– Structural engineering (§ 49) following: emergency scaffolding: preliminary, draft, approval and final design (Lph 2 – 5); special services approval design (Lph 4) (AHO- issue 3, n. 4.5 survey of structure conditions, ...) transversal launching: preliminary and draft design (Lph 2 – 3)
Special services: production of 3D steel construction model in the framework of draft and tender design for submission to the steel works contractor (accelerated material order/work preparation); analysis of workshop design in view of compliance with approval design; consulting for construction site supervision; consulting for monitoring services.