Renzo Piano explaining the Polcevera bridge. Photo Herbert Wright
By Herbert Wright
A week before Christmas 2019, I met the great architect Renzo Piano in his offices near Genoa. We talked about the new bridge over the Polcevera river that he had designed to replace the Morandi Bridge, which fatally collapsed in 2018. Piano’s slender new bridge design is epic, sustainable, robust, and smart. I visited the fast-track construction site. I also explored the working-class district scarred by the disaster, set to be transformed with trees and red steel in a plan led by Stefano Boeri.
This article was originally published in Blueprint magazine no.368, January 2020
In August 2018, Renzo Piano was in Switzerland when he heard that a bridge had collapsed in his home town Genoa. ‘I thought, my god, which bridge?’, he recalls. Then it emerged that it was the 1,182m-long Morandi Bridge over the valley of the Polcevera river, the key road link between France and Italy since 1967. Piano says ‘the first thought was bad. Sometimes that bridge was full of traffic, it could be hundreds of casualties. The other thing, I know that bridge well. Depending on which part of the bridge collapsed, there are houses’. Thankfully, the 210m-long collapsed section and its support tower was just to the west of residential streets, and fell over railways, warehouses and the Polcevera itself. But there was traffic, and vehicles plunging up to 45m into a void which opened up in an instant. The death toll was 43. The catastrophe made international headlines.
The Morandi Bridge collapsed in August 2018. Photos (L) Antonello Marangi (R) Mauro Utetto
Since then, a simple but elegant new bridge been designed by Piano, it’s official approval was shooed in, finance approved, and fast-track construction is now underway. In addition, a radical park under the new bridge, the Parco del Polcevera, has been designed by a team led by Studio Boeri (see ‘Under the Bridge’, below).
‘I always love the idea of the bridge’, Piano says. ‘They connect. That’s why they should never collapse’. He started thinking about the replacement bridge after Genoa’s mayor Marco Bucci called. He is no political crony – Bucci heads a centre-right city alliance which includes Eurosceptic Italian ex-deputy-premier Salvini’s anti-immigrant Liga party, whereas Piano is an independent senator who’s donated his Senate salary since 2013 to projects with a social dimension, the latest in 2019 a house inside the Rebibbia Prison in Rome for jailed mothers to have time with their babies. As the Pritzker-winning architect with projects all around the world ever since the Centre Pompidou (with Richard Rogers, 1977), Piano has always been an internationalist. Some say there should have been an international competition, but with half a million vehicles every week diverting through madly winding smaller roads in Genoa, a new bridge was needed quick. And with national pride at stake, this was to be an Italian job. ‘In an emergency, this country can show capacity to do things’, Piano comments. ‘Unfortunately you need an emergency’.
Wearing a bright green jumper, Piano spoke in December at the Genoa offices of his practice RPBW, where he is based one week every month (instead of at its Paris office). ’To make a bridge is three or four years, it’s a long journey’ he says.‘That’s why we started to think about the column made of concrete, and the bridge [spans] made out of steel’. Concrete and steel were the ingredients of the bridge that collapsed, but it was very different. Structural engineer Riccardo Morandi designed it as a cable-stayed bridge with three 90m-high A-frame towers, and unusually the cables were steel encased in concrete. Piano notes that ‘the traffic it had to support was at least three times what it was designed for’. Libya closed a similar Morandi project in 2017, the Wadi el Kuf bridge (1972), after inspections revealed potential concrete fractures. Piano does not blame Morandi for the collapse — he was ‘one of the two big [Italian] engineers after the war’, he says (the other ‘of course was Pier Luigi Nervi’). What was not understood then was how concrete corrodes. ‘People thought it was a miracle, a liquid that becomes solid. [But] stone is made in a million years, concrete is made in a few hours’, says Piano. He explains that ‘when concrete is covering steel, you have micro-pixellation, the mini-cracks inside, [and] especially in a salty atmosphere like in Genova, you have the start of corrosion inside’. Morandi became aware of these issues, and had urged regular maintenance at Genoa and elsewhere. The cause of the collapse is still unconfirmed and under investigation, but Piano says ‘that bridge needed affection and maintenance and attention… It’s not my job to judge people, but quite clearly that was not done’. Bridge operators Autostrada per Italia, part of a group which the Benneton family has invested heavily in, continue to contest accusations of poor maintenance.
After Bucci’s call, Piano immediately zoomed in on Google Earth to the terrain below the bridge. The Morandi Bridge had spans up to 210m long, but Piano had the idea ‘of maybe taking 50-metre steps, and taking a bold step when you cross the river. You need a bridge that puts its feet in the right place’. He indicates how the bridge tip-toes across the valley by walking his fingers along the edge of the table we sit at, illustrating the line of columns on site. When the road emerges from tunnel on the west side, it will pass onto a new steel deck that crosses seven 50m spans between columns. Then, as Piano says, ‘ you have to do double… jump-jump-jump’ — three 100m-spans over industrial land, the Polcevera river and railway lines respectively. On the eastern side, another six 50m spans and a final one of 40.9m to the meet the road before it forks, loops and disappears again into tunnel.
RPBW’s elevation blueprint of the new Polcevera bridge, courtesy RPBW
In all, there are 19 spans over 18 concrete columns section, carrying 1,067m of road on steel decking. It’s a beam bridge, the simplest structural form, with just columns or piers to carry and distribute load. In this case, the columns are 9.5m x 4m ellipses in section, minimal and elegant. There are two existing beam bridges which Piano has designed — the Ushibuka Bridge (1996) in Japan, carrying 900m of two-lane road across the sea, and the 190m-long pedestrian Nichols Bridgeway (2009) which connects Millennium Park with the Modern Wing of the Chicago Institute he designed. Both have a curving underside, like a boat. That’s not just because, as Piano admits, ’I love boats, all sorts of boats’. First, there is an aesthetic effect from the curve. Because of it, Piano explains, ‘the light is gently touching the underneath. It’s not a bridge with light [and] shadow’. The Chicago bridge is just 4m wide, but in Genoa, it’s 30m wide, so the effect takes on an epic scale. ‘I wanted to do this in such a way that when you are underneath, you look up, and it’s like a long ship crossing the valley’, he explains. ‘Normally you don’t see ships from below, but they are beautiful from below’.
Polcevera bridge cross section, courtesy RPBW
And there are practical benefits from the shape: ‘The hull makes sense… structurally speaking, it’s perfect. You support in the centre, then you fly on the side’. A hull is also hollow, crucially enabling internal access for maintenance (of which more later). Further, Piano saw the chance of having shipbuilders on board in construction, ‘because they know how to go fast in making the hull of a ship’.
Looking at the 1990 sketch Piano made of the Ushibuka Bridge’s cross-section, we pretty well see a draft for the bridge over the Polcevera. There is extra structure at the edge of the deck structure’s cantilevers. In Japan, either side carries a line of angled rectangular baffles which protect the peripheral cycle lanes from wind. In Genoa, there will be no cycle lanes (it’s a motorway), but each side will carry a 2.5m-high glass wall, and beyond it, a line of angled photovoltaic panels. They should generate more energy than the bridge consumes with its lights, plant and smart systems, making its operation carbon positive. Indeed, RPBW has been considering the potential use of an old rusting gasometer by the bridge’s western end — ‘it could be a reservoir of energy’, Piano muses. High-tech systems, which we will come to, will require energy, but the most visible demand will be the road lighting on twenty 28m-high central spires spaced every 50m. An initial concept rendering had light poles on either side, apparently making 43 markers for the dead. ‘It’s a nice idea but it’s a bit rhetorical in some way’, says Piano. ‘This idea of celebrating the dead with 43 candles… I think the celebration of a tragedy is only possible by silence’.
Cutting noise is a key part of the design. The streamlined deck and elliptical columns will reduce wind noise, and as for the traffic, Piano explains that ‘we use a special finish on the asphalt, and also we have the glass barrier’. The Morandi bridge had erupted loudly from each hillside, both visually and acoustically, but Piano says ‘this one is more gentle. It’s a kind of passing across the valley almost like asking permission’. Still, Piano’s bridge is certainly not trying to hide. His bridges in Japan and Chicago are both white, but this will be even whiter, with an optical gloss (the mirror-like reflective quality) of about sixty per cent.
But what about the key issue of maintenance? The new bridge enables it inside and out. ‘That’s a secret about ships’ says Piano. ‘They are maintained because you can reach the structure outside with the dry dock – this is like a ship on dry dock, permanently – and you can go inside’. Like a hull, the deck’s crescent-shaped cross-section is hollow, and with almost 5m depth at its centre, a gangway runs along the spine for the bridge’s full length. A dehumidification system will resist corrosion. Finally, RPBW are also working with the Genoa-based Italian Institute of Technology, which has one of Europe’s largest robotic research centres, on two robots, which will each move along one edge of the bridge. They not only clean the glass and solar panels, but each has a long arm curving under the bridge, which can be extended so that it can reach to the centre when not at a column, to monitor the whole underside.
Piano presented the initial new bridge concept on 7 September 2018, just 21 days after the collapse. He said his bridge would last a thousand years. And as with another of his three previous bridges — the pedestrian Ars Aevi Bridge (2005) over the river Miljacka in Sarajevo, where snipers had held sway — he offered the design for free. Approval was swift. Two global Italian companies— construction group Salini Impreglio and shipbuilders Fincantieri — formed a consortium called Per Genova (‘For Genoa’), to which the €202 million delivery contract was awarded in December. Work on the modular steel deck sections was allocated to Fincantieri’s shipyards at Sestre Ponente in Genoa and in Naples, and its Verona factory. Naples unveiling the first completed one in February 2019. Two months later, deep piling for the first column started. In June, the last of the Morandi was blown up.
Five columns on the bridge’s western side are spanned with steelwork in this December view looking east. Photo Stefano Goldberg
How has progress been on the ground? With a workforce numbering around 1,000, it continues round the clock. The steel deck comes in sections, some arriving by barge in Genoa. 50 tonne modules are transported by road in the night. On site, there are cranes with a lifting capacity of around 1,000 tonnes to lift sections assembled on the ground and weighing 600 to 800 tonnes onto the columns. By December, columns on the east side were still under construction, but two completed ones were already spanned by decking. All seven columns on the west side were complete, and three spans in place. The steelwork will amount to 15,000 tonnes, with another 9,000 of steel to reinforce concrete (although not near the surface as in Morandi’s time). The yet-to-be-named bridge’s opening had been targeted for mid-April, but is now expected in early summer.
Construction work, with Ansaldo factory and Polcevera channel behind. Photo Stefano Goldberg
It used to be that engineers would design bridges, architects designed inhabitable structures, and builders would build them. Piano is fond of reminding people that he comes from a family of builders, and has always felt that ‘architecture, engineering and building, they are the same thing’. That is visibly the case on the Genoa construction sights. He says a bridge is an ‘an architectural job… because it is about geography, it’s about topography, all that’. He adds that ‘it’s also about flying. The bridges fly, from one point to another’. Ever since his first lightweight structures in the 1960s, Piano’s work has been characterised by a sense of lightness and light. The new bridge across the Polcevera is solid and heavy, but it looks slender and light. The flight it makes will be through natural light, even at night when that light is recycled.
Renzo Piano at RPBW Genoa. Photo by Herbert Wright
Under the Bridge – Red Steel and Trees for a district of Workers and Industry
In March 2019, Genoa launched an architectural competition to revitalise 23 hectares of the Polcevera valley area under the new Genoa bridge. It was billed as ‘one of the most important urban regeneration projects in Italy’. In October, Milan-based Stefano Boeri Architetti won the competition, with a team that included Amsterdam-based Inside Outside, Milan-based studio Metrogramma and others. The winning entry is called Polcevera Park and the Red Circle and (was due to go on site) this spring.
Rendering – Polcevera Park and the Red Circle. Courtesy Stefano Boeri Architetti, Metrogramma Milano, Inside Outside | Petra Blaisse
But first, what is the existing territory under the bridge? This is a working-class district, which Boeri describes as an ‘area made of iron, water, cement and asphalt’. The west side of the Polcevera river is industrial, including the massive historic red-brick factory where Ansaldo Energia make turbines. It was in the shadow of the bridge but still stands. On the east side, swathes of railway lines sandwich two residential streets, one of which, Via Walter Fillak, was straddled by one of Morandi’s now-demolished 90m-high A-frame supports. Some of the six-storey residential blocks under the bridge were demolished after the collapse and their residents rehoused. Now, a banner hung on the street proclaims R-ESISTONO, meaning Resist-Exist. On a footbridge just north of the bridge, a line of flowers and wreaths make a poignant contrast to the line of new concrete columns just downstream of them.
Via Fillak, December 2019. Photo Herbert Wright
Polcevera Park sets out to revitalise the area. Boeri is known for incorporating trees into the studio’s designs such as the Bosco Verticale, Milan (2014), and his Urban Forest manifesto is a call for global action to counter climate change. There are a lot of trees in the Polcevera plan. The parkland is landscaped by Inside Outside with different species planted in strips of land with paths. It produces what Boeri calls ‘vital chromatic and botanical variety’. In the west the park descends from the lower valley slopes and gasometer to the riverside factory zone, and lines of trees continue across the river, in the residential strip, and along the foot of the eastern valley side. They amplify the way the territory has always been a composition of lines parallel to the river. Via Fillak, already lined by trees, will open into a new piazza under the new bridge, and artist Luca Vitone has designed a circle of 43 trees commemorating the dead, which he describes as a ‘forest’. There are zones of contemporary ‘smart’ industry under roofs collecting solar power, and facilities including an exhibition garden, playing fields and a new railway station.
Most dramatically, the territory will be crossed by the Red Circle, 500 metres in diameter, carrying a 6m-wide pedestrian/cycle path of steel raised some 10m above ground. Boeri says it symbolises ‘the powerful local tradition of blast furnaces, cranes, and overhead cranes’. On its southern side is a 120m-high energy-producing Wind Tower, also painted red. The linear geometry responds to Piano’s flying horizontal line, and the dramatic red seems to recall the visual impact of Bernard Tschumi’s steel installations (1987) dotted around the Parc de la Villette, Paris.
This area was active and far from being rust-belt, so some might say the plan brings gentrification. But there has been consultation with community and stakeholders. The idea of a carbon-neutral quarter full of trees, which creates community facilities and connectivity without cars, could give Genoa a showcase for masterplanning in the time of climate emergency.
Remembering the 43 dead from the Morandi Bridge collapse
Flowers at the Polcevera, December 2019 Photo Herbert Wright