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Why Clifton rock is music to scientists’ ears

Nanoscientists don’t care how much rumpus Willmott Dixon make building their Bristol home, as long as it’s vibration free when complete.

Project report Project Centre for Nanoscience and Quantum Information
Value £7 million
Client University of Bristol
Main contractor Willmott Dixon
Procurement Design & Build
Concrete contractor Febrey
Facade and curtain walling SIAC Construction

For Large images of the project click here

A lot of people look up to the University of Bristol. Not only is it a well recognised centre of excellence in subjects ranging from aeronautical engineering to veterinary science, but its campus is parked on top of a hill and looms above the rest of Bristol city centre.

The university works hard to keep its name among the elite of research and educational facilities. But in order to be able to continue to attract the best and most learned research professors, it must make sure its facilities are capable of carrying out cutting edge research.

The latest scheme that the university hopes will help keep it at the forefront of the latest scientific advances is the new Centre for Nanoscience and Quantum Information.

Main contractor Willmott Dixon Construction, working out of its Bristol office, is closing in on the completion of a scheme that should deliver the university the quietest building in the world.

This isn’t about adding a bit of extra acoustic insulation in the walls to try and deaden the noise of the traffic outside so that researchers can concentrate on their studies. No. This building is barely allowed to vibrate at all.

The reasoning behind this is simple. Scientists at the centre will be carrying out experiments on such a minute scale that even the slightest vibration could throw the whole experiment off skew.

“Amongst the experiments likely to be carried out here are ones where we move individual atoms around. As you can imagine at that scale it becomes extremely important that there are no vibrations to influence the experiment,” explains Professor Noah Linden, lead academic on the project for the University of Bristol.

Broadly, what happens is that the effect of the albeit minute vibration is amplified, not dissimilar to the way tea will spill over the side of a cup if there is even the slightest tremble in the holding hand.

For Willmott Dixon operations director Clive Pople and operations manager Dave John, the project has given them the chance to stretch their construction skills.

“We have never done anything as complex as this,” says Mr Pople, “It has certainly been a challenge. We are moving into such new territory that every detail is unexpected.”

The four-storey building is squeezed into a tight site alongside the existing department of physics and will link into the existing building at each level, a feature which brought its own problems.

Perfect geological feature

“We cannot afford to have any vibration from the physics department disturb us,” says Professor Linden. “Everything has to be de-coupled.”

What that means is that at every interface between the two buildings there is a 50 mm thick elastomeric jointing strip which helps keep them isolated from each other, ensuring that any vibration sourced in the physics department is unable to bridge the gap between.

Even the foundation pads are isolated using the elastomeric strips and the fear of vibration caused by a range of sources has been chased down throughout the design of the building.

Fortunately for both the University of Bristol and Willmott Dixon there is a geological feature that has ensured the project team can truly minimise vibration throughout the reinforced concrete structure.

The huge slab of limestone from which the university overlooks the rest of the city, known geologically as the Clifton Rock, has also been the project’s anchor stone. The 25 m x 15 m basement features a slab of up to 3 m thick which is quite literally bolted to it.

The thinking behind the idea is that by casting the reinforced concrete basement slab directly onto the Clifton Rock and using a series of ground bolts to lock it in position the building actually becomes an extension of the Rock formation itself.

By giving it this colossal mass there is little chance of the building being able to vibrate through impact from external sources. Seismic activity may influence it but the likelihood is considered too remote here.

Nevertheless, the very real fear that some degree of vibration will interfere with the microscopic experiments has forced the project team to look at how even the materials used to build the project will themselves affect the completed structure’s permanence.

The basic reinforced concrete frame building belies the level of sophistication inside it.

Deep in the basement four of the laboratories feature specialist flooring systems designed to minimise the impact of even the slightest vibration.

In two of them 2 m x 1 m x 1 m monolithic concrete inertia blocks are set into the floor on elastomeric bearings and will form the base to which huge steel tables, themselves sitting on air springs, are bolted ready for scientists to set up their experiments.

Another two of the laboratories feature 3 m x 4 m keeled concrete slabs which once again rest on air cushions. These enable different types of experiments to be carried out at the centre.

The frame itself is, admits Professor Linden, completely over-designed as far as traditional structural loading and performance is concerned. Its 450 mm thick reinforced concrete floor slabs are probably 200 mm thicker than they need to be but the hike in dimension is all part of the plan to reduce vibration through pedestrian footfall. Cast in-situ stairs are isolated from the rest of the building and the lift cores through more 50 mm elastomeric strips.

Ingenious Faraday cage

Radiation - in terms of its definition in physics as energy in the form of waves - takes many forms and even the electromagnetic force emitted by standard steel reinforcement bars is too great for them to be safe to use in the laboratories.

The steel bars used to reinforce the concrete in the basement inertia blocks have been replaced by plastic while all the laboratories located in the basement are encased in foil-backed plasterboard helping form a protective shield against electromagnetic radiation, called a Faraday cage.

The curved entrance sail facade features cladding based on a mathematical sequence known as Fibonacci numbers, and is isolated from the building for fears that vibration from the wind may travel through it.

A further feature on the roof - the glass ‘Buckyball’ skylight representing the Carbon 60 molecule - is also isolated from the building to prevent vibration.

Pipework, central heating system and electrical conduits sit on more elastomeric strips in a bid to exclude interference and it is, Professor Linden admits, a project that has evolved since its inception five years ago.

“We could never say ‘Here’s the brief’ because it is difficult to specify what is achievable. There is no such thing as being quiet enough,” he says.

For Large images of the project click here

How willmott dixon went beyond Design & Build

In the broadest sense of the term the deal Willmott Dixon has with the University of Bristol is a design and build contract. But this does not reflect the amount of continual effort put in by both client and contractor to make sure the project is not out of date before it has even been completed.

In this fast moving area of science, future proofing the project has been an ongoing task – and one that meant that Willmott Dixon has had to work more closely with the university than it might normally expect.

“It is a design and build contract but what we have is not a traditional building,” says Willmott Dixon operations director Clive Pople, “We have had to go back to the client and make sure we are not compromising the performance of the final structure.”

That level of excellence has forced the project team into a number of design tweaks, the largest being the complete revamp of the ventilation system.

The initial design meant that not all of the laboratories could have their individual ventilation systems turned off, a major flaw when experiments are so sensitive that control of the local climate could be crucial.

“Redesigning and changing that system cuts across the whole design and build philosophy,” says Paul Cooper, University of Bristol deputy director of capital projects, “But it had to be done to ensure we got the right end result.”

Spreading the news about nanoscience

The new Centre for Nanoscience and Quantum Information at the University of Bristol is not the largest building in the world but in many ways that could prove to be one of its best features.

In the building, specially designed ‘interaction spaces’ have been incorporated to encourage researchers to share information about their areas of expertise.

“There is one common space where people from other disciplines will have to talk to each other,” says Professor Linden, “It will help knowledge transfer between the disciplines.”

Nanoscience and nanotechnology focus on the fact that well understood materials can actually behave differently at a microscopic level.

A nanometre measures just one millionth of a millimetre and the differing behaviour some materials exhibit at this scale could allow them to be used in a raft of previously untried applications.

Elastomerics and construction

At the University of Bristol’s new Centre for Nanoscience and Quantum Information main contractor Willmott Dixon is using elstomeric jointing strips to help stop any vibration travelling into the building and ruining experiments.

But what are elastomerics and how else can they be used in the construction industry?

Elastomers and elastomerics are simply polymers – a substance formed of repeating units that are connected by chemical bonds – that feature elastic properties.

They have been used in the construction industry for many years – rubber is an elastomer – but now the focus is on the development of high performance materials such as silicone, urethane foam and thermal and electrically conductive rubber.

The molecular structure of the elastomer is such that it can be compressed and stretched under loading but will return to its original shape and in the case of the material used at Bristol features good sound and vibration absorbing characteristics.

This is partly because of the complexity of its molecular structure – vibrations get lost as they try to work there way through it.

But it is not just in sound and vibration isolating applications that elastomeric compounds can be used in construction.

They can be more commonly used as bridge bearing plates which transfer loading and any movement from the deck into the structure and down through into the foundations.

An elastomeric bearing will enable any movement by the deck to be accommodated by it moving and distorting when under load.

And it is this ability to contort under loads which has attracted roofing companies. As a building moves over time traditional flat roofing materials can crack and wear but an elastomeric roofing system can absorb this movement, reducing the likelihood of cracks developing and extending the life of the building.