Control and Isolation of Low Level Vibrations in Civil Engineering Structures – ENG- PhD (Funded)

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Structural Testing of a Heritage Railway Bridge

On Thursday 1st June, a team of researchers from the University of Exeter travelled to Watchet to perform testing on the Mineral Line Bridge. The bridge forms part of the West Somerset Railway, a heritage railway line with 20 miles of track in South West England. The team included Farhad Huseynov, Yan Xu, Jalil Kwad, Karen Faulkner and Linus Tonui.

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Locomotive passes over the Mineral Line Bridge

The Mineral Line Bridge is located on the outskirts of Watchet and was originally constructed to carry the Minehead route over the West Somerset Mineral Railway. The Mineral Railway now operates as a footpath and cycle path open to the public. The bridge opened in 1962, has a single span of 14 m and is constructed skewed to the pathway beneath.

The aim of the testing was to measure the structural deformations of the bridge under loading from passing trains, a combination of steam and diesel engines. A series of strain sensors, inclinometers and LVDT sensors were installed on the bridge. A number of targets were also installed on the bridge to measure deflections using an Imetrum camera.

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Jalil Kwad installs the strain sensors on the bridge

The strain sensors were installed below deck at mid-span, with the inclinometers installed above deck at each support, and quarter-span. Data was recorded during each passing train.

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Imetrum cameras and targets installed on the bridge

The Imetrum camera was used to measure deflections of the bridge under loading from the passing trains. Three Imetrum cameras were set up on tripods and targets were installed, one at mid-span on the bridge deck and two on the western abutment, previously identified as an area of interest.

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The team in action, Yan Xu (front), Farhad Huseynov, Linus Tonui and Jalil Kwad (left to right)

The weather conditions were favourable, sunny with low winds. This led to limited interference from the environmental conditions, allowing for a clearer understanding of the train loading on the bridge.

Photo E
Raveningham Hall locomotive passes over the bridge

Dubh Artach Lighthouse modal test

Dubh Artach Lighthouse, Southwest of Mull on the Scottish West Coast was designed by Thomas Stevenson (father to the author Robert Louis), first ‘exhibited’ in 1872 and fully automated in 1971.

As part of the EPSRC STORMLAMP project, a team visited the lighthouse on 8th and 9th May 2017 to carry out a modal test. Alessandro Antonini took the modal test equipment by van from Plymouth University while James Bassitt and Karen Faulkner from the University of Exeter’s Vibration Engineering Section travelled via Glasgow Airport.

Dubh Artach helipad is just above sea level, so, as well as usual weather restrictions, helicopters (flying from the Trinity House depot in Oban) can only visit at low tide. Luckily, the weather was excellent, with zero cloud cover, perfect visibility and minimal wind.

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Karen Faulkner watches helicopter lift off from Dubh Artach Helipad.

Access to the lighthouse is via vertical steps and all equipment, including a 50 kg shaker, had to be hoisted to lantern level using a temporary crane.

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Access to lighthouse via steps, equipment hoisted by crane.

The signal to noise ratio for forced vibration testing was perfect, providing extremely clear resolution of vibration modes, with the shaker mounted on the lantern level walkway, just visible in the photograph.

 

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Drone view of lighthouse with shaker at 6 o’clock position on lantern walkway.

Conditions were also perfect for flying the survey drone, providing some stunning views:

After staying overnight on the lighthouse, the team returned to Oban, then to Exeter and Plymouth.

 

Modal test of Jiangyin Suspension Bridge

As part of the EPSRC-funded BAYOMALAW project, a team of researchers from Exeter and Liverpool travelled to Jiangyin in Jiangsu province, China to carry out a modal test of the Jiangyin Suspension Bridge.

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Jiangyin Bridge has a single suspended span of 1,385m, with straight back stays. The concrete towers rise 191m above ground level and each have three hollow portal beams. The mid portal is illustrated by the bridge name in stylised Chinese characters, created by (and signed by) the former Chinese premier Jiang Zemin, who opened the bridge in 1999. At the time, the bridge was the world’s fourth longest span and the furthest downstream on the Yangtze River.

The 32.5m wide 3m deep steel box deck carries three traffic lanes (plus a narrow emergency lane) in each direction. There are 2.2m wide cantilevered walkways either side, although these are for maintenance as there is no pedestrian access to the bridge. These walkways were used by the test team for moving the loggers around.

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Test team (left to right): Yu, Zhen from Jiangsu Transportation Institute (JSTI), James Brownjohn and Karen Faulkner from Exeter,  Yichen ZHU from University of Liverpool and James Bassitt from Exeter

The exercise was primarily an extreme test of the capabilities of two new technologies.

First, a new synchronised wireless logging system was created by James Bassitt (hardware) Vincent Ao and Emma Hudson (software). Four loggers were taken to China (as checked baggage) with a set of 12 force balance accelerometers and a set of short signal cables.  These loggers are synchronised to a fraction of a microsecond before a measurement then distributed over the bridge deck and towers in a sequence of measurements to record ambient vibration signals.

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James Bassitt and Karen Faulkner synchronising the loggers at the start of a day of measurements.

Some 14 separate measurements were made over a period of three days (25th-27th April 2017). For each measurement, the master logger was left recording vertical and lateral vibrations continuously at hanger locations H67 and H71 on the east walkway (there are 85 pairs of hangers each side) while other (slave) loggers were ‘roved’ to record for at least an hour synchronously at other locations on the east and west sides and inside the south tower.

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James Bassitt and Karen Faulkner move slave logger to a new measurement location.

The weather conditions were mostly benign; cloudy, cold, hazy and breezy on the first two days, clearing to a fine sunny day for the tower measurements. Due to pollution and unpleasant atmospheric conditions resulting from the heavily industrialised area around Jiangyin, team members wore protective face masks most of the time.

The second major technology being evaluated was the operational modal analysis planning and evaluation procedure developed by Professor Ivan Au as part of the BAYOMALAW collaboration with the University of Liverpool.

BAYOMALAW stands for ‘Bayesian operational modal analysis law’, and the main aim of the project is to establish uncertainty laws for modal testing to optimise tests such as these. BAYOMALAW aims to establish the best measurement configurations and the resulting uncertainties in modal parameters in terms of natural frequencies, damping ratios and mode shapes. Jiangyin is an extreme test because of its ultra-low natural frequencies and its weak lateral response buried in quasi-static effects of deck rotation.

As part of the procedure, a ‘huddle test’ is used to check the self-noise and environmental noise of the measurement system. To do this, all sensors are huddled into one location and sense either vertical or lateral vibrations simultaneously.

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Huddle test of measurement system at H69

The exercise required a large investment of resource into building, programming, delivering and operating the system on site – but preliminary analysis of the data shows that the exercise was a success and that everything worked. The test was funded by the EPSRC and supported by Tongji University and JSTI.

Testing the dynamic properties and performance of a building under human-induced excitation

Emperor House is a modern office building currently under construction at Exeter Business Park, UK. The three-storey building has an internal floor space of 2400sqm, which consists of two wings and a central core.

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In collaboration with Summerfield Developments (SW) Ltd (client), WSP-Parsons Brinckerhoff (consultant) and Midas Group (contractor), the Vibration Engineering Section (VES) at the University of Exeter successfully carried out a test of the building’s dynamic properties and performance under human-induced excitation.

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State-of-the-art equipment was utilised in the test to identify the modal properties of the first floor of the building and perform extensive walking tests.

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The test results will be analysed in detail. The final aim is to help structural engineers to design such buildings at minimal cost, while vibration serviceability requirements are maintained.

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VSimulators: Human factors simulation for motion and serviceability in the built environment

Vibration Engineering staff led by Professor James Brownjohn have been awarded a £3.25m grant by EPSRC to create a new simulator facility for study of interactions between humans and the moving built environment. The simulator will use a mechanical hexapod to drive a 4 metre square platform in all 6 axes with accelerations and displacements representing typical movements of a range of civil structures (floors, footbridges, grandstands) where comfort of human users and occupants is critical.

The simulator will be fully instrumented with an array of force plates, inertial and optical motion capture and head mounted virtual reality for nine occupants.

This grant is part of a large investment by EPSRC and both Universities of Exeter and Bath; a University of Bath team let by Anthony Darby have simultaneously been awarded a £1.65m grant for a complementary simulator for study of large amplitude building sway at low frequencies typical of tall and super-tall buildings.

Co-funding from Universities of Bath and Exeter for infrastructure, additional equipment and staffing beyond the three year initial EPSRC funding amounts to £2.42m, and the total project cost will be £7.25m.

VSimulators will provide cross-disciplinary capability to address deficiency of information on human factors, environment and structure motion on engagement with the built environment:

  • For slender sustainable structures, e.g. tall buildings, vibration serviceability is a critical design constraint poorly (if at all) addressed by design codes, hence a need for bespoke customised acceptance criteria.
  • Effects of low level vibrations coupled with sound/noise, light, pollution, smell, temperature, humidity, and other environmental factors which contribute to the mysterious sick building syndrome.
  • Mobility and rehabilitation in an aging population cost the National Health Service £bns per year. Rehabilitation of motion-impaired patients is a major problem.

The Exeter investigator team comprises:

James Brownjohn                   Principal Investigator, Structural Dynamics

Alex Pavic                               Co-Investigator, Vibration Serviceability

Paul Reynolds                         Co-investigator, Vibration Control

Vicki Goodwin                        Co-investigator, Healthcare, Rehabilitation

Mateusz Bocian                      Co-investigator, Virtual Reality

The Bath team comprises:

Antony Darby                         Principal Investigator, Structural Engineering

Sukumar Natarajan                Co-investigator, Environmental Design

David Coley                            Co-investigator, Building Occupant Behaviour

Ian Walker                              Co-investigator, Environmental Psychology

A facility manager is being recruited to work with research and commercial users to maximise facility use. Experimental officers will manage operations at the Exeter and Bath sites, James Bassitt at Exeter will supervise the Bath EO.

The international advisory team are:

Kenny Kwok                           University of Western Australia

Tracy Kijewski-Correa        University of Notre Dame

Yukio Tamura                        Tokyo Polytechnic University

Robert Brown                        Memorial University, Newfoundland

Industrial support for VSimulators is provided by AKT II, Arup, Atkins, Buro Happold, Emirates DNEC Engineering Consultants, Flint&Neill (now COWI), Foster and Partners, Swallow Acoustics Consultants (now part of Thornton Tomasetti), Waterman Structures and WSP|PB.

VSimulators is affiliated to UKCRIC and will be a national research facility available to RCUK-funded researchers for research projects as well as to private industry at commercial rates.

Links to publicity in national and local media can be found here.

Impact of wobbly bridges and sky-scrapers on human health to be tested in government-funded research centre

The impact of vibrations from very tall buildings and wobbly bridges and floors on people’s health and wellbeing is to be researched in a new £7.2 million government-funded national research facility.

Check out the rest of the story about the launch of VSimulators on the University of Exeter’s website

http://www.exeter.ac.uk/news/featurednews/title_574555_en.html 

In the meantime, here is some other coverage of the story:

Wobbly skyscrapers may trigger motion-sickness and depression, warn experts (Source: The Telegraph)

Did you feel the earth move? (Source: The Plymouth Herald)

Exeter and Bath get £7.2m to find out if wobbling is bad for us (Source: Devon Live)

Do YOU work in a skyscraper? Wobbly high-rise buildings may trigger motion-sickness, insomnia and depression (Source: Daily Mail)

Wobbly skyscrapers may trigger motion-sickness and depression, warn experts (Source: MSN Health)
Are skyscrapers making you sick? A new £7 million study is trying to find out (Source: Architecture magazine)
Are tall buildings good for your health? (Source: About Manchester)
VR vibration simulators set up to study effects of working in a skyscraper (Source: Engineering & Technology)
Universities to set up lab to measure fear and nausea caused by tall buildings (Source: Global Construction Review) http://bit.ly/2nr89Rc

 

Launch of Novel Vibration Control System for Floor Structures

The result of many months’ work on an EPSRC funded project was revealed on 16th February at a launch event for a novel vibration control system. The event attracted directors, associates and senior engineers from major companies including WSP, Atkins, Foster and Partners and Arup. They witnessed the launch of a proof-of-product system, which was developed by Professor Paul Reynolds and Dr Emma Hudson to address the current gap between the proven academic successes of active vibration control for floor structures and the lack of adoption by industry to date.

The technology works in a similar way to that of popular noise-cancelling headphones: an accelerometer is used to measure the vibrations of the structure; the resulting signal is processed by a real-time computer and then an actuator generates the required force to cancel out the measured vibrations.

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This new product combines all these components into one standardised compact unit that can be more easily installed within structures. Crucially, the system has been developed with robustness and minimised cost as priorities, to complement the proven high performance of this technology. In this way, the system is significantly more commercially attractive to potential adopters, meaning that the benefits of enhanced vibration performance are now a step closer to being realised.

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A lunchtime seminar was organised at the Institute of Structural Engineers HQ in London to highlight the potential benefits of this new product to key industry contacts. A joint presentation by Paul Reynolds and Emma Hudson was followed by a live demonstration of the new system.

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