However, soon those news bulletins willhave a new visual symbol.  Almost unnoticed by those outside Frankfurt, the ECB has been building a new headquarters, which will provide a striking addition to the Frankfurt skyline, and will create a single base for the ECB’s operational activities as it manages the currency of one of the world’s largest economic areas.
 
ICE Germany was fortunate to be able to visit the construction site in August 2012, and to hear from some of the engineers involved in what is a complex project, involving the restoration and adaption of a huge protected building, the Grossmarkthalle, and the construction of a landmark double office tower soaring to a height of 185m.
 
The Grossmarkthalle,Frankfurt’s former wholesale market hall, was built between 1926 and 1928.  At the time it was the world’s largest fee-spanning reinforced concrete structure, and was the city’s tallest building.  The market was relocated in the 1990’s and the city was looking for a new use for the site.  The ECB purchased the site in 2001, and an architectural competition resulted in a winning design, by COOP HIMMELB(L)AU of Vienna, which provides a glass-panelled high-rise in the form of a double office tower linked to the Grossmarkthalle by an entrance building.  The cavernous interior volume of the Grossmarkthalle encompasses the ECB’s public facilities.
 
ICE Germany’s site visit started with aseries of three presentations. Our first talk was by Wolfgang Strehle, of Ed. Züblin AG in Stuttgart, who described the construction of the towers.  If you imagine taking a standard high rise building of rectangular cross-section, and slicing it vertically in two with a giant cheese knife, but rotating the cheese knife slowly as you lower the knife, then taking the two halves of the building and placing them back to back, you will have something like the ECB towers.  For good measure make one of the end walls slope inwards from bottom to top.  Then add connecting interchange platforms at 50m height intervals, and glaze the connecting space to form four atriums. 
 
The landmark design gave those constructingthe towers the challenge of a geometry which changes with every floor.  The concrete cores of the towers are erected by means of a mast climbing work platform.  The floors are constructed using formwork tables. A clearly visible yellow band, about three storeys high, has surrounded each tower as it has grown.  The band is a debris mesh which serves as a shield to allow formwork and concreting to continue in bad weather and strong winds.  The interchange platforms and additional steel trusses serve to brace the two towers.  The trusses were manufactured in parts off site, then assembled on site and craned into position, and will remain visible as features of the enormous atriums.
 
Herr Niewirth, of Ed. Züblin AG in Darmstadt, then spoke about the construction work involved in the renovation and conversion of the existing Grossmarkthalle.  The existing structure consists of 16 reinforced concrete portal frames at 15 m spacing and each spanning 43 metres, giving a total building plan of 240 m by 43 m.  The roof consists of 15 thin concrete shells, each spanning 15 m between adjacent portal frames.  At their vertex the shells are only about 75 mm thick.
 
The new ECB entrance building “cuts through” the existing Grossmarkthalle structure, at a location chosen deliberately to coincide with the part of building reconstructed after war damage, so that the parts of the structure which escaped damage in the war will still continue in the new building.  The renovation work includes (i) structural renovation work, including renovation of the concrete, the beams, the concrete shells and the brickwork, to ensure structural stability for the future, and (ii) restoration work to restore the original 1928 design.  By the time of our visit most of the external restoration and renovation work was complete, and the restored brickwork in the walls was looking just as Martin Elsaesser, the original designer in 1926, would have wanted it.
 
The afternoon’s presentations finished with a talk by Professor Manfred Grohmann of B+G Bollinger und Grohmann, Frankfurt, on the structural design of the towers.  After sharing some insights into the difficulties of designing a structure with such a challenging geometry, Professor Grohmann led us in a fascinating round table discussion on the role of contractors in managing large construction projects such as the ECB.
 
We then stepped outside, put on the customary site visit attire, and were given a guided walk around the site by Yorck Förster of the ECB Communications Directorate.  He proved a knowledgeable guide, pointing out many details of the original construction of the Grossmarkthalle, and how the challenges of complying with both listed building regulations and modern energy-efficient building standards had been met.
 
Following our thanks and goodbyes, we adjourned to a traditional Frankfurt East End “Wirtschaft” to enjoy traditional Frankfurt fare.  Whether the pub will keep its unspoilt charm when 2,300 ECB staff move in across the road in 2014 remains to be seen.  Thanks go to Hamish Douglas for organising such a fascinating site visit, to the ECB for facilitating the tour, and to our hosts Züblin for providing the venue for the presentations.
 
Hamish Douglas CEng FICE, ICE Representative for Germany, Chairman of the European Sub-Committee and Council Member for Europe, organised this visit to the ECB.
 
Graham Murnane CEng, ICE Member in Germany, submitted this report.