Klassenhäuser: Structure



Comparing flexible slab constructions

Innovative solution

Otto Wulff / Ehoch3 / Hamburg University of Technology

Partners Involved

School buildings

Building type

(Prefabricated) Concrete, steel, timber

Structural material

Structural system

Flat slabs supported on beams / columns and walls

It is expected that faster construction progress can be achieved with the use of flexible connections. This would result in economic and ecological/environmental advantages.

In Hamburg, several comparable schools are being built with the same concept. For CIRCuIT, the design of two of these are compared and the differences in the approach are highlighted.


A special focus will be placed on the comparison of the conventional in-situ concrete method with pre-stressed concrete cast elements, as well as with prestressed concrete elements with seam and joint. Furthermore, a bolted timber-concrete construction method will be considered.

Another aspect that is interesting regarding the CIRCuIT project is that the ceiling constructions created can be dismantled completely.

The expected impacts

It is expected that with the flexible construction method, it will be possible to demolish more purely by type in the future, which will result in less mixed construction waste. This increases the overall recycling rate of mineral construction waste for higher-quality applications. This also results in less mineral construction waste being landfilled and the necessary landfill bodies lasting longer.

Another aspect is that the demolition of flexibly constructed buildings is easier to carry out in theory, which means that this can be done more quickly, which is associated with a saving in labour time.

Activities done

  • The influence of different construction methods was investigated. The influence of these on individual building elements as well as the influence on the entire building was considered.

  • A complete BIM model of all 3 construction methods was created to investigate the impacts and quantity changes of the building materials.

  • The digital model was analysed with BIM quantity takeoffs and can be used for visualisation and representation of the differences and materials used.

  • The components were evaluated for demountability and reusability. Possible constructive improvements to increase the demountability and the associated possible reusability were identified. Different ceiling systems were examined in more detail.

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Demonstrated results

  • Optimised slabs can be dismantled completely sorted by type. The amount of concrete for the floor slabs is 40 % compared to the in-situ concrete construction.

  • The joint sealing of the prestressed concrete slabs can be omitted due to geometric interlocking. This makes it possible to completely dismantle the elements without sorting them during deconstruction. 

  • The concrete hybrid construction resulted in a building that was over 50 cm higher, with corresponding effects on wall heights, staircase and railing lengths, and pipe lengths. The spans had to be reduced, which caused conflicts with the functional/architectural goals.