Barcelona’s disused Las Arenas bullring is being transformed from a crumbling wreck into Richard Rogers’ vision for a leisure and entertainment venue, topped out with a UFO-style roof.
When you first set eyes on Las Arenas, your natural reaction is to blink just to check you aren’t seeing things. An entire bullring hovers 5 m in the air. And it is only after blinking that you notice that the whole thing is being held aloft by a series of spindly struts. Walk cautiously under these walls and another shock is waiting: the ancient walls of the bullring teeter on the edge of a 26 m deep hole where bulls and matadors once fought for their lives.
What is the point of these extraordinary structural gymnastics? Well, the modern trend of turning unusual old buildings into retail and leisure facilities has finally struck at the heart of what was one of Spain’s most venerated traditions, albeit one that is in decline in Barcelona. A project to transform the bullring into a leisure and entertainment venue was only commercially viable if 1200 cars could be parked underneath the building, as the tight site is in the middle of Barcelona, and right next to a Metro line. Furthermore, the bullring is on a raised site, meaning that its foundations are actually 4 m above street level.
These factors presented structural engineer Expedition with a unique challenge. “It’s a mega retained facade made complicated by the five storey basement and the fact the ground has been lowered underneath the bullring by a storey,” says director Chris Wise. “You might do one of these things on a project, but not all three and survive.” But survive he has, with the help of the project management arm of Bovis Lend Lease who have been responsible for overseeing the work of Spanish contractor Dragados.
A disused and neglected treasure
The whole crazy idea came about by chance. Laurie Abbott, a senior director at architect Richard Rogers Partnership, happened to drive past the abandoned Las Arenas one day with Spanish architect Luis Alonso. “I said that’s interesting and asked Luis what was happening to it, and he said ‘nothing’,” says Abbott. Alonso offered to approach the site owner who agreed to a meeting with Abbott. “They said if you want to make a proposal that’s fine. It was a gamble on our part.” It was a gamble that paid off as the site owner agreed to go along with the idea.
Abbot worked closely with Wise on the proposal. Despite the technical difficulties both men wanted to retain the bullring as part of the scheme. “It was a nice, strong simple building and I’m sure the people of Barcelona would want to keep it,” says Abbott. “It was also an interesting technical problem.”
The people of Barcelona might be fond of Las Arenas, but they had not done anything to look after it. It was abandoned in the 1970s after a spell of being used as a venue for bands – The Beatles played there once. It was in such poor condition that the plan was to rip out the old stands leaving just the perimeter wall, which according to Wise was the only element worth hanging on to. “When we surveyed the wall we found it was in a terrible state. It was full of rusty old iron, pigeons were nesting in it and it was leaning over by up to 350 mm,” says Wise. “In some places if we had taken the parapet off the wall would have fallen over.” Indeed the wall was in such a bad state that bits were falling off it – a woman was seriously injured by falling debris before work started.
The first job was to stitch together large cracks in the walls with metal bars. Then work could commence on supporting the facade so the mound of earth on which it sits could be removed, leaving what was left suspended in mid air. This is part of the final architectural solution; the idea is people can wander freely into the new building under the old facade, which acts purely as a visual element. The new building and the roof will be entirely structurally independent of the original wall.
Supporting the facade
Ultimately the facade will be supported on a series of V-shaped steel supports. But it had to be temporarily propped so the earth mound could be excavated and the permanent supports slid into position. Four mini piles were sunk under each arch in the facade. Then 15-20 m long sections of earth were excavated under the foundation so formwork could be positioned to cast curved concrete beams on either side of the old wall – these ring the facade and will distribute the point loads from the supports evenly around the fragile walls. Holes were drilled through the wall to correspond with holes cast in the beams. Threaded steel bars were inserted through these, enabling the two concrete beams and the old wall sandwiched between them to be clamped together as one unit. The old wall turned out to be hollow, so concrete was used to fill the cavity.
The mini piles were attached to the concrete beams and temporary supports erected to laterally support the facade. Work could now begin on demolishing the bullring interior and lowering the earth bank on which it was sitting down to street level, ready for the next delicate stage of the job, which was to construct the five-storey basement.
The adjacent Metro meant digging a vast hole then building the new structure was out of the question. “Because of the Metro we have had to construct the basement using top down construction,” says Peter Gibney, the construction manager for Bovis. “The fear was that with the underground water and the earth pressure, the whole thing could have caved in.” Top down construction means building the structure first, then excavating the earth afterwards. In this case, the structure consists of a retaining wall to hold the earth back around the perimeter of the basement, and a series of piles to support its concrete floor slabs. Only the structure adjacent to the old facade is being built using top down construction, as this will keep the surrounding ground in place and support the facade. The basement and slabs in the centre of the bullring will be built conventionally once the perimeter structure is complete.
The retaining wall is outside the facade as the basement extends underneath it. A 60 mm wide trench the depth of the basement had to be excavated for the retaining wall. “There was a lot of rock so the teeth of the scoop were constantly getting broken,” says Gibney. A mechanical hammer could be used to break up the rock but only in areas well away from the Metro. Once the trench was excavated it was filled with reinforcement and concrete.
Piles were also sunk ready to support the floor slabs. These were inserted in a circle inside the old facade, and also outside in the places where the retaining wall is further away from the original facade and the slabs need additional support. Plunge piles were used to ensure the piles were vertical. A large hole was bored then a guide plate was fitted at the top and the steel column inserted into the hole. A weak concrete mix was poured in around the column to ensure it stays in the correct place. It can be removed later.
Once the structures were in place underground, the ground-floor slab was cast. This contained cast-in beams to transfer the weight of the retained facade – which sits in the middle of the slab – to the structure on either side. Once the slab was cast, the ground underneath it could be excavated down two floors so the next one could be worked on. The intermediate floors will be put in later, in tandem with the structure in the centre of the bullring.
Currently Dragados has reached level –4 and only has to excavate down another 3 m to reach the lowest point. But being below the water table is causing problems. “We are now pumping out water and are delayed as we didn’t start pumping early enough,” says Gibney. Once the water level has been reduced, more piles will be sunk inside the bullring to support the roof structure, which will sit on four big piers. Then the lowest level slab, a 1 m thick raft foundation will be cast and the comparatively straightforward work of completing the basement in the centre of the bullring, and the rest of the building, can begin.
The project value is £68m, and Dragados is doing the bulk of the construction work for a fixed price of £42.5m. The contract to install the services will be let separately. The developer is Sacresa, the largest developer in Catalonia which is owned by a firm called ACS, who also happen to own Dragados. The fact Dragados is doing the construction work is largely coincidental. Originally the job was going to be let package by package, but Dragados made the best offer. But the fact that the contractor is owned by the client has inevitably made life less comfortable for project manager Bovis. “Its difficult to manage,” concedes Gibney. “Dragados probably aren’t pleased we are here as we make their life more difficult.”
This is because Bovis has the responsibility to deliver the job on time, and to ensure it stays on budget. But this is Spain, a country where patience really is a virtue. “You can’t rush things in Spain, you have to go with the flow,” says architect Abbott. The completion date was originally January 2007, then slipped to January 2008 and is now set for May 2008. “It’s gone over the provision for a variety of reasons,” says Gibney. “These include the client not giving authorisation to proceed, issues with the retaining wall, problems relocating utilities and delays directly attributable to the contractor.” He adds that because the client owns Dragados it is reluctant to apply financial penalties for delays, which is frustrating for the project manager. Gibney would have preferred a construction management role, which would have put him more firmly in the driving seat.
Despite the delays, Gibney says the work is good quality and is coming in on budget, as unexpected costs such as having to temporarily alter local road layouts to enable work to continue are being balanced by judicious value engineering by Bovis. For example money was saved on the retaining wall by proving it could sit on higher areas of solid rock, thereby reducing its depth. Money was also saved on reducing the depth and diameter of the piles, and the line of the retaining wall was changed to avoid adding to the burden of expensive utilities relocation. “There was a massive job relocating services as many of these weren’t chartered,” says Gibney. “You had to get the utilities in and ask which of these were live or dead. They said ‘we will get back to you’ and all the time Dragados was beating us around the head as they wanted to get on.”
The UFO look
Las Arenas will consist of five floors of mixed-use leisure and entertainment above the basement. There will be multiplex cinemas, shops, restaurants and a health club at the top. There will also be a separate office building and a telecoms tower adjacent to the bullring.
One of the building’s most striking features is its roof, which Wise describes as “the UFO”. It is dome-shaped and supported independently of the retained facade and the rest of the building by four, tree-like series of columns. The roof structure is a timber gridshell, which according to Wise will be one of the largest ever built. The space in the roof under the gridshell will be used for cafes and restaurants with a terrace running around the edge allowing views over the city.
There will be a 2.5 m gap between the retained facade and the new building inside. This has walkways for maintenance and is used to route services around the building. The top walkway is used as a running track circling the building. Big springs are used to connect the new building to the delicate old facade as changes in temperature will cause it to expand and contract. “We didn’t want to lock the wall to the new building, which is a much more rigid structure,” says Wise. “The walkway is like a giant, squidgy shock absorber.”
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