• Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed
  • Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed Project: Grain silo repurposed

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Project: Grain silo repurposed

Online since 29.01.2017 • Filed under Project • From Volume 5 - 2017
Project: Grain silo repurposed

The historic grain silo (The Silo) situated in the Victoria and Alfred Waterfront dates back many years to a time when most of the country’s trade was conveyed on the high seas or via steam train. Completed in 1924, the Silo dominated the skyline of the city at 57m tall.

 

Constructed by SA Railways and Harbours, the facility consisted of a suite of buildings including the storage annex, elevator building, dust house, dust cyclone and track sheds. The facility processed hundreds of thousands of tons of wheat, maize, soya and sorghum. It was sited to take advantage of its connectivity to the docks and the supporting rail infrastructure. An iconic building, it is considered an important contributor to Cape Town’s urban character. Consequently, it is heritage-listed by Docomomo South Africa (See http://www.docomomo.com and https://goo.gl/CgFD3O) . By 2001, the old Silo had become redundant.


The Silo District

The Silo now lends it name to and forms the centre piece of a new district within Cape Town’s famous V&A Waterfront, a redevelopment project which started in 2010 as a mixed commercial, residential and leisure hub to the east side of the V&A and connecting it with the CBD.


The overarching vision for the former grain silo is to redevelop and restore it so that it attracts national and international interest, bringing it to life as a new cultural centre for the City and the continent as a whole.

Referred to by V&A Waterfront Development Manager, Mark Noble, as ‘the cathedral at the centre of the precinct’, the Silo has been given a remarkable makeover and will shortly house one of the world’s largest collections of African contemporary art from the continent and across its diaspora.


A partnership between the V&A Waterfront and Jochen Zeitz will create the Zeitz Museum of Contemporary Art, Africa (MOCAA). The museum will be spread over 9 floors and will total nearly 10,000m2 with over 5,000m2 of dedicated gallery space. It is expected to open on 24th September 2017. In addition, a 28-room boutique hotel  has been developed directly above the museum, rising five stories above the elevator building section of the silo. This will soon be occupied by the Royal Portfolio hospitality group.


SA Building Review was given an exclusive tour of the project by V&A management which we are proud to share with our readers.


Suitability as a museum

How does an organic building such as a grain silo morph into a breathtaking gallery, housing a premier art museum and a boutique hotel? Principally, the former silo consisted of two functional areas:

• An elevator building which received, hoisted and then gravity-fed incoming grain from a rail loading point to various storage bins inside the complex.

• The storage annex – the major storage areas consisting of 42 large individual silo ‘cylinders’ measuring 5m diameter by 30m high.


By clearing out a portion of the highly compartmentalized internal structure it was possible to create a series of exhibition spaces.

The intention was to convert most of the total existing volume to 80 separate gallery spaces, education spaces, reading rooms, meeting and conference space, plus a huge atrium area beyond the main entrance, rising 30m and 20m across. This atrium occupies the space of 12 of the former silo cylinders and is arguably the most imposing feature of the new building. Walking into this chamber, one is given the impression of being in space – weightless and shaped with massive curved dimensions.


Suspended overhead, the impression of zero gravity is provided by gigantic ‘hanging’ silo cylinders (as cut) which form the concentric ring arch above. The top of the bins is capped with a glass roof which lets light enter the atrium from above. The bottom of the atrium is formed by graded steps that naturally contour the rounded space forming a flexible amphitheatre space that can be used for both events and displays.


In addition, a rooftop floor is dedicated to a restaurant, an education centre and a rooftop sculpture garden. It is from this level that visitors may embark on their ‘walk of faith’ across a highperformance glass floor that looks down into the atrium. Visitors arrive on this level by using one of two scenic lifts. These lifts operate inside two of the cut-away silo cylinders – with a view into the atrium. A third adjacent partly cut-away silo provides the third panoramic option – a steel spiral staircase. There are also conventional service lifts and the usual fire escape staircases, in line with standard building safety requirements.


By way of a design element that is a first in Africa, Zeitz MOCAA will be served by Category A climate control in the galleries. The technology has been endorsed by the International Council of Museums (ICOM) and is used in internationally renowned galleries such as Pompidou Metz, Pulitzer and Paul Klee. The technology offers the highest level of protection to a collection and is the most advanced climate control technology available at present. It will allow MOCAA to exhibit any piece of art, no matter how fragile. In line with other V&A Waterfront buildings, much of the climate control is based on renewable energy – in this case the chillers utilise the district sea water plant.


The mealie pip concept

The vision for the atrium contemplated by principal designer Thomas Heatherwick, CBE, is graphically articulated in a V&A Waterfront YouTube video interview. In his own words: ‘Inside we were in danger of losing the extraordinary cellular structure, so we created a space that would help you (the visitor) understand the building. So, you would walk in and navigate around. We took the idea of taking just one of those billions of grains of corn so that we could scale it up and use it as a (model) for the cutting tool to cut through’. Innovative aspects and features of the Silo are many. While a single article in SA Building Review is insufficient to explain the full extent of design and engineering innovation with readers, we mention only the highlights.


Cutting of the individual silos and their lining

A major engineering design feature of the new building and one which ‘makes it hang together’ is the engineering treatment of the individual silo tubes and cylinders that formed the annex.


The atrium itself – jackets and sleeves

A core concept in reinforcing the strength of the remaining silo tubes so that they could be left in place and cut to the architect’s design, is the use of an inner concrete ‘jacket’. Using concrete supplied by AfriSam to engineer’s specification, the inner circumference of each silo tube was re-lined with 200mm thick reinforced concrete to its exact cut dimension.


‘The new concrete was poured into formwork within each atrium grain silo exactly to the shape of the new atrium. This formwork was set out in each tube in isolation from the next using a complex 3D model to provide the relevant data points which were then translated using basic surveying techniques to an accuracy of plus-minus 50mm over the entire atrium,’ says Noble. A 50mm deviation over this huge edifice is truly exceptional.

‘The relining of the circular silo tubes was the first activity to take place. This new concrete structure forms the primary structure for the building, without which the old silo tubes could not be altered.


Specialist form work was created in conjunction with PERI Formwork and then lowered by crane into each tube. Each pour was approximately 3m high. This can be clearly seen on site, particularly around the lifts,’ he explains.

Once the new concrete structure was cast inside the old tubes and connected across the top to create the concentric ring arch structure, the newly set concrete was then used as the guide or template to cut the old structure. Two types of cutting machine were mainly used; the double blade and the diamond rope.


The discarded concrete sections were cut into 1 ton blocks by large diameter diamond circular blades and then lowered to the floor to be carted off site. After the cut-away part of each silo tube had been lowered to a height of 18m above the slab, a 20 ton machine specially brought in, demolished the remaining tube walls. Waste material was recycled or in the case of steel beams, was reused as temporary bracing during construction.


After much effort, the atrium area was cleared. Then a highly skilled specialised polishing team directed by master polisher, Johan Lotz, moved on site and has been painstakingly at work for several months polishing the surfaces of the walls.


The remainder of the silo annex

The eastern half of the annex, consisting of the 24 remaining tubes, was re-sleeved around its entire perimeter and then supported with façade retention supports.


After this, circular silos inside were hollowed out as follows.

• First the façade (with its reinforcing jacket) was cut away using large diamond blades, releasing it from the throw away central portion. At the same time, sufficient structural fins were left inside to support or retain the façade.

 • The internal tubes and bins were then demolished and the rubble removed before the excavation into the building foundations could begin to create the eastern core.

• A new reinforced concrete frame inside the perimeter was then constructed once the eastern section core had continued past the first level.

• This new frame was tied into the façade at each level to provide full structural integrity. The concrete structural fins were demolished one floor at a time. At the same time, the adjoining re-sleeved sections were joined at the central point to create the perimeter column structure, vital in transferring perimeter loads down to the foundations.


Once the reinforced concrete frame was complete inside the annex, work begun on building the individual gallery ‘white boxes’ which would house the art. ‘The walls are simple dry lining with plaster board noggins to take the art. The floor is a raised access floor to create the necessary underfloor plenum to allow the displacement ventilation system to work,’ says Noble.


Use of pillowed windows

The museum itself has a series of pillowed windows that surround the lift lobby on level 6 (the top of the erstwhile silo tubes), the restaurant and events space and the sculpture garden. A distinctly shaped set of windows set in a steel frame were fashioned offsite by Mazor Glass and delivered on site. Each unit takes only minutes to be set in place once raised by crane to the level. The hotel above the elevator building has five floors with these windows, allowing generous sweeping views across the harbour and beyond.


 Walking on glass

Above the atrium, on the level of the art sculpture garden, visitors will be treated to the rare experience of walking across suspended glass. Using a similar material to that used at the Eiffel Tower and the ‘Gherkin’ building in London, the high-performance glass was supplied by St Gobain France to their Lite-Floor Xtra Grip specification.’The glass includes a special ceramic fritting to prevent solar heat gain and was designed by a  famous artist – literally including art into the fabric of the building’ adds Noble.


Original bins and equipment

To preserve the building in the best way possible, parts of the large steel storage bins of the elevator building and lower level of the silo annex were first removed to facilitate demolition and construction and then replaced as part of the building’s display of history. The basement of the building gives an accurate feel of how the silo worked – a virtual rabbit warren of tunnels where grain flowed down and out into bins and was taken up via conveyor belts to the elevator, where after it was transferred onto the external conveyor out to the loading terminal on the quay.


Outside

Much has been done to retain the original look and feel of the former grain silo, except for the hotel extension on top of the elevator building and the curious looking pillowed windows. To preserve the façade of the building, the base concrete was treated with a specialised concrete repair product.


South African and English built environment specialists have used the most awesome technology in putting together a completely legendary project. It is truly worthy of international recognition at the highest level.

 

The writer acknowledges with gratitude the time and effort given by the V&A key project personnel, especially Fran Ventura and Mark Noble, in providing access to site and for the highly thought provoking site tour – GG

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