Vibration engineering spin-out creates safer structures for industry

Published on: 12 November 2014

Students at work in the new £1million structural engineering lab.

National sport stadia such as Premiership Football grounds and the London 2012 Velodrome plus chimneys in power stations, office buildings and bridges are just some of the structures that have been made better performing and more economically viable thanks to work with the University of Exeter’s Structures and Dynamic Group and their spin-out company Full Scale Dynamics Ltd.

Using technologies and methodologies usually reserved for aerospace – such as modal testing of aircraft - and applying them to the civil engineering and construction industries, the company can improve performance of structures, and have, on numerous occasions, helped avoid potentially serious economic and safety consequences due to the poor vibration performance of structures.

Full Scale Dynamics Ltd use their specialist vibration testing facilities and in-house analytical facilities to investigate the long-term performance of structures in addition to identifying any specific flaws during or after construction. They can help companies save money by using novel analysis procedures yielding lighter and more economic structures, such as long span floors, tall buildings or long bridges.

Data on how to use ‘dynamic loading’ of crowds of people helped Professor Aleksander Pavic, Professor of Vibration Engineering and Managing Director of Full Scale Dynamics Ltd with one of the team’s most high-profile projects - helping the design team behind the London 2012 velodrome save 400 tonnes of steel.

Dynamic loading due to humans is used in the design of grandstands, stadia and seating decks. Professor Pavic explained: “When people are jumping and bouncing on grandstands and in tiered seating we have to find out if they are going to dynamically excite the structure a lot or not, is it going to shake too much or not.

“We helped Expedition Engineering save 400 tonnes of steel after being asked to verify independently their approach. The analysis procedure they used was novel and was recommended by a national design committee for crowd dynamic loading on grandstands and seating decks, which I was on. My job on that committee was to provide experimental data on the real-life performance of grandstands.”

Research expertise

The top technical expertise of Full Scale Dynamics Ltd is in measuring real-life performance and learning what is going on from those measurements. Professor Pavic said: “In commercial civil engineering, real-life performance of large structures is rarely measured, everything is based on established and never checked codes of practice and design guidelines, so each structure is in essence a unique prototype.”

In the construction industry research and development activities are very limited so the company acquire high quality research data through their commercial contracts and pass that back to the University’s Structures and Dynamic Group.

Professor Pavic explained: “There is some data our clients need to acquire because of contractual obligations, and we are using this commercially acquired data and spinning it into high quality research data."

“Without having access to the data from the company we would lose an important feedback loop between office design based on guidelines and the real-life performance of such designed structures. Structural engineers tend to be conservative and wasteful because they are overcautious and operate within a very litigious sector.”

Research group

Full Scale Dynamics Ltd works in tandem with the Structures and Dynamics Group to provide the institution with legal and operational framework to access unique and high-value research data at short notice that would otherwise be difficult to acquire through normal research route. In return, the Company has access to the state-of-the-art University facilities.

Professor Pavic built the research group and company together with his colleagues Professors James Brownjohn and Paul Reynolds over a number of years at the University of Sheffield. When they moved to Exeter they brought their research team and the company with them.

The group have generated the world’s largest databases of operational performance data of floors, stadia and footbridges and of ground reaction forces due to humans walking, running, jumping, bouncing and even - standing. They also contributed to the solution of the problem of the wobbly London Millennium Bridge in 2000, which occurred when the structure became unfit for purpose because of a lack of understanding of the interaction between the walking crowd and the bridge structure.

The company is run as a normal business, but it would be difficult for it to operate outside a university environment because of the high level of skills, technology and expertise needed to operate in a relatively small market.

Laboratory

Professor Pavic explained: “We are underpinned by a £1million laboratory, which is killing two birds with one stone: the equipment is used for fundamental research and provides industry with difficult to procure state-of-the-art structural performance assessment service. The company creates unique impact, such as saving 400 tonnes of steel on the Velodrome and is hence pushing all the right buttons as far as government agenda for research impact is concerned while providing the industry with the best possible service.”

He added: “We operate in an area where the UK has been at the leading edge for many years – and on top of that we also do high-quality research. There are not a lot of areas where the UK is ahead of the USA and this is one of them.”

Professor Pavic and his team will be inspiring a new generation of structural engineers through the launch of a new MSc Structural Engineering course. Students will have access to a new purpose-built world-class laboratory, unique in the UK, with state of the art equipment and facilities. The new lab is dedicated to better understanding vibration serviceability including in-situ testing and monitoring structures. It features:

  • Unique and reconfigurable prototype floor or footbridge structure weighing up to 15 tonnes with surface are of up to 50m2.
  • Instruments capable of measuring dynamic structural movements from metres to nanometres.
  • Ambient and forced vibration testing equipment.
  • Unique systems for active and passive control of vibrations of large structures, like floors.
  • Individual and group human motion tracking and measurement systems suitable for in- and out-door operation.
  • State-of-the-art motion capture facilities optimised for field usage.

Students will have access to this lab and it facilities and will learn how to design and measure performance of large and slender structures which meet the demands of today’s global construction market.

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