Erecting the diamond dome

Erecting the diamond dome


For the architecturally stunning new Vienna Central Railway Station project, Unger Steel Group embraced Tekla’s BIM software to plan, produce and assemble diamond shaped trusses for the roof of the station

Unger Steel Group is an Austrian group of construction companies with long experience in structural and architectural steel construction of projects. The group was commissioned to plan, produce and assemble 14 diamond-shaped steel trusses of the partially transparent, architecturally stunning roof of the new Vienna Central Railway Station, a major European traffic hub. The steel trusses had to be placed 15 metres above platform level. Another major challenge was the station was a development project with an attached shopping mall, residential buildings and a park, and work had to be done with precision on a crowded site and in close coordination with other parties. Unger needed a comprehensive solution to manage logistics, create constructible steel structures, model and detail structure and sub-structures, and collaborate with project parties like architects and structural engineers.

The challenge
The roof was 5,000 tonne processed steel with an area of 40,000 square metre. Each steel truss was 76 metres long and had one-of-a-kind appearance. The roof could not have any horizontally arranged component. Such a structure had to have nothing less than 254,000 screws, 54,100 frames and 271,100 metal sheets. Unger had to create 52,700 individual and 22,200 welded components. Safety, precision and timelines were the first of many challenges Unger had to face.

The solution
At Unger, BIM does not stop to the design office door. The company configures each new version of Tekla Structures according to their standards, enabling it to plan specifically for their cutting and production machines. It uses Tekla in tendering for informed estimations during bidding; even its salespersons are familiar with Tekla BIMsight.

For the Vienna Central Station, Unger created all transport lists and surveys directly from Tekla’s BIM model and used it to control production and assembly sequence. Tekla created constructible steel structures, modelled and detailed the main structure and substructures like cable channels, and extracted data and drawings for production and assembly, simulated welding sequences of the complex components. The Unger team imported the architect model as 3D DWG files to Tekla Structures for designing and detailing the diamond trusses. As numerous project parties operated on the huge construction site, Unger also included platforms with rails and concrete foundations to the model to notice possible clashes in the design phase.

Unger chose BIMsight for planning transportation lists since the work had to be done on time. For production at workshop, the required data transferred directly from design office to DSTV and interfaced with the cutting machines in workshop.

The Trimble Total Station helped assembly of roof components while they hung from a crane, and the team needed exact position data for lifting and fitting the components at 15 metres above the platforms. With the Total Station, Unger’s own staff could measure the structures and save on expenses of external surveyors. A combination of Tekla and Trimble solutions were used in a preassembly workshop to measure the components after welding to spot possible manufacturing tolerances before assembly, and later to control the position of the structure.

BIMsight offered detailed information to carry out each task with great precision. As a result, the site staff was already assembling the first diamonds at the station while the workshop team produced the remaining ones. The entire process from cutting one truss to its final assembly took about three-and-a-half months.

Results and benefits
BIM and automated data transfer accelerated the project while easing the logistical challenge with automatically generated transport lists and aid in controlling production and assembly sequence. The measurements of the built structure were transferred directly to Tekla, saving time and labour because there was no manual data entry. The BIM solution ensured that each project party had the building information model available and could work together, including production and installation teams on the site. Unger started work in 2010, and the first trains arrived at the station in late 2012, and passengers could get the first glimpse of the city through the roof. The station is scheduled to be fully operational in 2015.