In the middle of the project, the engineers from Thormahlen + Peuckert successfully adopted the Allplan Bridge solution for modelling a challenging bridge design in Lower Saxony
One of the most important foundations for success in general but also one of the core principles of pilot projects is learning. It’s about finding out what works and what doesn’t.
As part of the German government’s efforts to promote digital design and construction, a large number of infrastructure projects are currently being carried out where the foundations for BIM are being developed. In the BIM pilot project, A1 Motorway: Bridge Replacement Over the River Hase and the Stichkanal, in Lower Saxony, near Osnabrück, northern Germany, the dedicated bridge modelling solution, Allplan Bridge, was selected in the middle of the project – a learning curve which paid off.
Replacement for a seven-span bridge from 1969
Due to the high volume of traffic, the A1 motorway between the Ahlhorner Heide interchange and the Lotte/Osnabrück interchange has been widened from four to six lanes over the past several years. This expansion required six construction phases and includes a seven-span bridge built in 1969 between the Osnabrück Nord and Osnabrück Hafen junctions. The 261.5m long structure crosses the Osnabrück branch canal (including the service road and embankment section), the Hase watercourse, as well as unpaved areas in the floodplain and a service road with an adjacent ditch.
Structural analysis showed that the bridge does not have sufficient load-bearing capacity in the longitudinal and transverse directions. According to the experts, the target load level could only be achieved with a new replacement structure.
Preferred option: Canal and foreshore bridge
The client, the Lower Saxony State Authority for Road Construction & Traffic, commissioned Thormählen + Peuckert with an optioneering investigation in the course of the preliminary design, as well as with the modelling of the preferred option for the construction of the new replacement bridge.
The engineers designed a total of nine options, with the structure separated into a canal bridge and a foreshore bridge in each one. Preference was given to an option consisting of a tied arch bridge with a span of 68m over the canal crossing and a subsequent foreshore bridge as a two-span plate girder with two integral support axes and variable headroom. The individual spans of the foreshore bridge vary between widths of 25.8m and 56m.
Change to Allplan Bridge
Once the preferred option had been decided upon, it still had to be modelled. The alignment axes, in particular, posed an enormous challenge, as they differed in the two-directional lanes and required, among other things, a complicated cross-sectional widening of the carriageway leading to Dortmund.
The engineers soon realised that such was the complexity of the task and the time constraints involved that a new approach would be needed. Thus, they decided, during the ongoing project, to implement Allplan Bridge, the dedicated bridge solution that supports the entire design process.
Parametric bridge model with Allplan Bridge
In Allplan Bridge, they were able to create a parametric bridge model that automatically generated correct geometry based on the values entered. For example, for the Dortmund carriageway, variable slab widths for the channel bridge could be easily modelled for arch compensation or cross girder heights for slope compensation could be adjusted using Boolean operators for constant carriageway slab thickness.
Error-free modelling thanks to Allplan Bridge
Hendrik Martin, project manager for structural engineering/bridge construction at Thormählen + Peuckert, is enthusiastic about the benefits the switch provided.
“By switching to Allplan Bridge during the ongoing project development, we succeeded in achieving error-free modeling of the new replacement canal and foreshore bridge on the A1 motorway near Osnabrück,” he said.
“Allplan Bridge makes it possible to implement complex structural designs and to adapt them to demanding route layouts. Arched structures in composite construction with subsequent semi-integral and haunched prestressed concrete structures could thus be harmonised despite differently positioned gradient girder axes.”
ALLPLAN GmbH
Twitter: @allplan
