North Rhine-Westphalia State Archive: the structural optimisation of extension tower thanks to Cofrastra® flooring deck

Detailed information

Urban planning and architecture

The brick-clad reinforced concrete granary of the Rhine-Westphalia Shipping Corporation's warehouses was built in 1936. On a total of eight storeys, grain was stored in the form of bulk goods. The precisely constructed concrete frame makes the granary a fine of example of a reinforced concrete building.

The NRW State Archive presents a monumental, brick-red figure to the A40 motorway and to the inner harbour of Duisburg. The existing granary building was augmented by the construction of an archive tower at its centre. The archive material of the state can now be housed in a strikingly visible way. The openings and roof surfaces of the existing granary were closed, and the new storage tower distinguishes itself from the old brick structure by the use of fine ornaments. The building provides space for archive material on shelving with a total length of 148 kilometres.
 
The foyer is at the interface between the old granary building and the adjacent newly constructed five-storey building, called The Wave due to its shape. This creates an appropriate entrance for the new state archive. The foyer and public areas open to the waterfront promenade, and in the interior of the foyer huge 'porthole' windows allow for a view of the collected archive material.

From here, the new building grows eastward into the site. The five-storey addition, which extends in a wave-like form along the inner harbour, contains the foyer, administration, and additional functions. The Ziegelplatz at the Schwanentor is emphasised towards the street space.

Archive Tower: architecture & structural design

The fundamental design element is a solid external skin of bricks that gives the 76 m high, 15-storey archive tower a sculptural appearance. Technical facade elements such as gutters and facade safety rails were made in such a way that they visually retreat to the background. The historic structure and function of the listed building remains legible.

A finely articulated ornament is made by means of projections and recesses in the brickwork. The existing walls consist of full bricks in the traditional dimensions of 25/12/6.5 cm. The newly erected external walls were built using bricks with the same format. The existing windows in the granary building were walled up with brickwork.
 
The colouring and texture of the new brickwork takes up the surface of the original bricks, which through their patina are a witness to Duisburg’s industrial history. The new and old building parts are subtly differentiated. 

Together with the engineers from Osd, the architects of O&O Baukunst developed the idea of building a 'storehouse in the storehouse' and integrating the new building as a tower within the existing granary building.

The structure of the new storage tower consists of outer reinforced concrete walls that transfer the horizontal loads and function as the building envelope and an inner steel construction that transfers the loads of the archive material. Open steel sections, protected with intumenscent paint, were used as columns and beams. The flooring system consists of composite flooring deck and on-site concrete.

Composite flooring system

ArcelorMittal Construction Germany supplied the steel deck for the archive tower's composite flooring system. In total, around 12 000 m2 of Cofrastra® 56 were used to optimise the structural system of the 76 m high tower.

Sustainability aspects

The archive building permanently preserves the documents of the State of North Rhine-Westphalia; accordingly, the building design aims at stabilising the climatic system and protecting resources. The long-term archiving provided here is reflected by the building’s robust design that conveys a sense of permanence.

• An air-tight construction to reduce air exchange with the external climate was achieved by closing up the windows in the existing granary building to eliminate the harmful effects of daylight and sunlight. An energy-efficient lighting system reduces internal heat loads.
• Entry to the archive rooms is regulated by means of air locks that reduce air exchange with other parts of the building. The length of stay in the depots is limited to two hours.
• All rooms have to be at least half-filled with archive material to achieve the planned humidity-regulating effect.
• Thermal insulation had to be mounted internally to preserve the external appearance of the listed granary building.
• Use of passive air-conditioning, augmented by a sensitively adjustable partial air-conditioning system, reduces the low internal loads. A constant relative room humidity is crucial as the archive material attracts moisture.
• Short-term fluctuations in air humidity and temperature must be avoided at all costs. Ideal storage conditions lie between a temperature of 16°C with a fluctuation of only +/-2° C and an air humidity of 50% with a maximum fluctuation of 5%.