Competition 1st prize 2017
Competition 1st prize 2017
Cooperative Migros Basel, Switzerland
Christoph Merian Stiftung, Basel, Switzerland
Herzog & de Meuron, Basel, Switzerland
Franck Mahler, Fabio Pesavento, Nico Ros, Sali Sadikaj, Kay Unterer, Manuel Wehrle
The transformation of the former duty-free depot Dreispitz in a mixed-use urban quarter is one of Basel’s largest urban developments since the start of the 21st century. As site owner, the Christoph Merian Foundation is funding this change, together with Canton Basel City and Migros Cooperative Basel, which has been operating at this location since the 1930s. The northern end of the Dreispitz site, right on the edge of Basel’s city centre, is simultaneously the eastern continuation of Gundeldingen, a so-called ‘Gründerzeit’ quarter.
Herzog & de Meuron’s winning project from the Dreispitz North competition was shown to the public in December 2017. It has since been significantly enhanced and concretised as a guideline project, and was presented as such in October 2020, forming the basis for the development plan, which is to be submitted to the Basel City Cantonal Parliament for approval in mid-2021. ZPF Ingenieure has been working on this project since the competition phase, in Herzog & de Meuron’s team.
Over the coming years, the large Migros Cooperative Basel shopping centre, with a hardware shop and huge car park, is to become a lively urban district with an identity of its own, thanks to a diverse mix of uses. Today’s asphalt car-park surface will be replaced by two spacious parks with plenty of greenery. In addition to 800 attractive flats, a renovated shopping centre of unchanged size, office and commercial spaces, a neighbourhood centre, a youth centre, cafés, restaurants, shops, leisure facilities and educational facilities are all planned. Moreover, Canton Basel City has decided to build a secondary school with a triple gymnasium on the large roof surface.
The shopping centre’s pre-existing support structures have load reserves that make it possible to install a parking level, along with a lightweight triple gymnasium or intensive greening, on top of the pre-existing construction, without having to carry out any interventions. For the transfer of horizontal loads from earthquakes and wind, bracing cores and shear walls are provided in the pre-existing building and in the extension.
The gymnasium on top of the pre-existing building is planned as a lightweight timber construction, with a flat pitched gable roof on a frame structure with suspended lattice girders and an axial grid adapted to the pre-existing building, so that loads are transferred directly into the ground through the pre-existing columns. The bracing of the gymnasium is geometrically optimised, so that only compressive and shear forces occur on the pre-existing slab.
The secondary-school building for around 600 pupils is on the uppermost floors of the new structure that is planned to stand alongside the Migros building. Up to the ground floor of the school, the pre-existing building’s load-bearing structure is continued as a reinforced-concrete skeleton. For the upper floors, i.e. the actual school, a change of material is planned, in keeping with the change of use. The support structure is conceived as a lightweight composite or hybrid construction in wood and steel, which not only reduces the building loads, but also enables acceleration of the construction process, due to the high degree of prefabrication. The vertical loads are transferred to the ground via the defined column grid and the foundation. The bracing is provided by optimally arranged cores and shear walls, which guarantee maximum flexibility for the users.
Townhouses and towers
Basel needs new housing, and 800 flats will be built at Dreispitz North. At the site’s northernmost point, seven townhouses with affordable and non-profit housing are planned. These buildings, with two underground floors and six or nine upper floors, are conceived in such a way that they have a flexible load-bearing structure, currently in the form of a reinforced-concrete skeleton. Load is transferred via slabs to columns and walls, down to the foundation. The bracing element is the access core, and the facades are designed to be flexible.
The round Dreispitz towers, with heights of 125 m, 140 m and 155 m, offer attractive flats with magnificent views, as well as space for offices and public-oriented uses, such as a library. These buildings are primarily braced by means of reinforced-concrete cores. The load-bearing structure is optimised so that as much vertical load as possible is transferred via the core in order to maintain overpressure in the core cross-section, even with horizontal loads, which has a positive effect on the dimensions of the core, as does a partial activation of the facade layer for bracing. The aim is to maximise the usable area between the facade layer and the core.
A lifestyle with low car-use is promoted in this new neighbourhood. Optimal public transport connections, new bicycle and pedestrian paths, sufficient bicycle parking spaces and new car-sharing models contribute to this, as does the arrangement of access routes to the above-ground and underground parking facilities on the surrounding streets.