Ultra-precise Calculation

Case Study

With TRIMAS, Dr. Geppert was able to model and calculate the entire load-bearing system of the western end including the complex load transfer within the entire structure.Graphics: Stefan Kimmich
In the western end of the building, loads will be braced via several steel framework girders and two steel frame constructions in the lower park decks of the superstructure, which together with the bracing cores result in a complex 3D load-bearing structure. As a view of this area on equivalent 2D systems would have led to major uncertainties in the analysis of the results, a three-dimensional model was created of the western end of the building including all ceilings, girders, cores and supports.

The current extension work at the Frankfurt AIRRAIL centre over Frankfurt’s station for long-distance trains posed various challenges for structural and inspection engineers. Precision work is called for here, as the bearing structure of the ends of the building is so complex that it cannot all be broken down into separate evaluation schemes.

Founded in 1976, König und Heunisch Planungsgesellschaft (KHP) of Frankfurt am Main offers a comprehensive range of engineering consultancy services from steel-reinforced, prestressed or composite steel concrete to timber engineering. The company’s main focus is on structural engineering, covering planning, contract award preparation, structural analysis to construction supervision and management. As several of the company’s owners are approved inspection engineers for structural analysis, structural engineering inspection is another of KHP’s core competences. With a workforce of more than 60 employees, the company attaches great importance to a high level of professional state-of-the-art competence and punctual completion however large the project may be. At the same time, the company’s engineers always keep an eye on the budget of their clients.

Fully linked

Dr. Klaus Schneider from KHP has been contracted to inspect the structural engineering evaluations of the AIRRAIL centre directly above the station for long-distance ICE trains at Frankfurt airport. This major engineering challenge is to provide a reliable link for road, rail and air traffic in a forward-looking building at the second largest airport in Continental Europe. 94,500 square metres of office space, 5,900 square metres for retail and catering, an imposing hotel covering 34,500 square metres: the figures alone are impressive. The centre is scheduled to open in December this year already. Ever since 2006, the construction site at Frankfurt Airport has been bustling with activities to meet the deadline of project partners IVG Immobilien AG and Fraport AG. The structural engineering part was done by a consortium of Krebs und Kiefer Beratende Ingenieure, S.A.N. Darmstadt GmbH for structural engineering and bwp Burggraf + Reiminger Beratende Ingenieure GmbH in Munich. Responsible for the execution planning of the building, which is being constructed under the project management of Ed. Züblin AG, were the architects of J•S•K Dipl.Ing. Architekten.

Ensuring the load-bearing capacity

Designed by Hadi Teherani from BRT Architekten, the Frankfurt  AIRRAIL centre was built in two stages. Resting on 43 fish-belly girders spaced 15 metres apart, the platform on which the new centre is to be built by the end of this year consists of a 28 cm thick steel-concrete slab in the shape of a surfboard. Like the glass dome that is to be retained as a roof over the entrance to the ICE station, it has been in existence for about ten years already. Two Hilton hotels have planned to move into the eastern end and the new headquarters of the Frankfurt KPMG is to move into the western part of the centre this year. No easy task for structural and inspection engineers, because the planned superstructure and the already existing construction have to be matched to each other. “The main challenge for the structural engineers was to apply the load of the building to the bearing points designed for the existing structure,” comments Dr.-Ing. Thomas Geppert, Project Manager for structural inspection at KHP. The geometry of these bearing points, which does not coincide with the grid of the superstructure, is already predefined by the truss geometry of the fish-belly girders. Extensive bracing structures were therefore required and the free placing of bracing cores and slab walls was extremely limited.

Firmly anchored

There is a special situation at the two ends of the long building, where the superstructure has an ascending overhang that projects so far beyond the last fish-belly girder that additional labour-intensive bracing structures were required. Due to the different uses of the two ends of the building, their structures are completely different. The eastern end is to have a 3D steel framework structure on the middle floors of the hotel where a ballroom is planned. The loads are passed on by steel pylons integrated via connectors into a bracing core. At the western end the loads will be braced by various steel framework girders and two steel frame constructions in the lower park decks of the superstructure, which together with the bracing cores form a complex 3D load-bearing structure. "A view of this area on separated corresponding 2D systems would have led to major uncertainties in the analysis of the results,” reports the project manager of Dr. Klaus Schneider’s team of inspection engineers. For the western end, therefore, Dr. Geppert created a three-dimensional model of the whole system including all ceilings, girders, cores and supports. To do this job, he used the FEM system TRIMAS of RIB. With TRIMAS, Dr. Geppert was able to model and calculate the entire load-bearing system of the western end including the complex load transfer within the entire structure. By using different layers within the model, the analysis of the dimensioning results can be reduced to individual components and the evaluation can be visualized in a clear and transparent way.

“We have been using the structural engineering applications of RIB for analysis and design tasks for more than 25 years now,” adds manager Klaus Wörner. Besides TRIMAS, several structural concrete design applications of the RIBTEC portfolio, such as BEST, RTbalken or ZWAX, were also used for the inspection engineering for the AIRRAIL centre. “The reinforcement of the 32 cores of the building is particularly easy to calculate with ZWAX,” he points out. “We’re glad to be able to rely on provenly successful systems for projects such as these.”



Industries>Architecture, Engineering & Construction>Architects and Engineers>KHP

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