Managing full scale dynamic performance of civil infrastructure
Submitting InstitutionUniversity of Sheffield
Unit of AssessmentCivil and Construction Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Mathematical Sciences: Statistics
Engineering: Civil Engineering
Summary of the impact
Research in the Department of Civil and Structural Engineering at the
University of Sheffield on dynamic performance and vibration
serviceability has contributed to internationally applied guidance on
building serviceability for floors, buildings, stadia and other structures
and has led to the spin-out Full Scale Dynamics Ltd (FSDL). Based on our
research FSDL provides applied research and consultancy services, and has
delivered projects approaching £1m since 2008. FSDL has demonstrated
significant reach through its work with blue chip clients nationally and
internationally. Our research has impacted on leading national sport
infrastructure (such as Premiership Football stadia and notably the
Olympic 2012 Velodrome) and public companies to deliver economic benefits
by providing evidence based compliance, demonstrating that stadia,
hospitals, manufacturing plants and other public structures comply with
safety and vibration serviceability standards. Interventions based on our
research and implemented via FSDL have, on numerous occasions, avoided
potentially serious economic and safety consequences due to the poor
vibration performance of structures.
Underpinning research in the field of vibration performance of civil
engineering structures was initiated by Pavic (Professor, joined Sheffield
1996) with the formation of VES (Vibration Engineering Section) at The
University of Sheffield, focussing on vibration serviceability of
structures. Reynolds (Professor, joined Sheffield 1998) extended this
research to dynamic performance of grandstands and developed active
vibration control systems. Brownjohn (Professor, joined Sheffield 2005)
brought in expertise on dynamic performance of tall and long structures
over wide ranges of time and length scales. In 2008 Pavic, Reynolds and
Brownjohn founded the Sheffield University spinout company Full Scale
Dynamics Ltd (FSDL) as a delivery mechanism for impact of the research.
Racic (Lecturer, joined Sheffield 2011) added expertise in experimental
characterisation and mathematical modelling of dynamic loading of
structures induced by active individuals, groups and crowds of people.
Our research led to novel approaches to management, design and in-situ
dynamic performance assessment of large civil infrastructure with respect
to fitness for purpose with complimentary attention to safety, comfort and
economy. Our research was partly funded via the award of an EPSRC platform
grant in 2009 (EPSRC EP/G061130/1), the first of its kind for this area of
civil and structural engineering research in the UK.
Our researchers capitalised on technology and methodologies for modal
testing typically applied to mechanical and aerospace structures, such as
ground vibration testing and finite element model updating of prototype
aircraft and transferred it to civil structure applications [R1]. Civil
structures differ substantially from mechanical structures in materials
and scale as well as in level and nature of vibrations. What worked well
in controlled laboratories had to be adapted through a series of research
projects (GR/L68742/01, GR/S14924/01) to work in open space environments
with challenging environmental and operational conditions and unusual
signal to noise ratios. Within these research projects we developed
systems-engineered tools and procedures that combine artificial forcing
and ambient excitation and linked simulations to assess fitness for
purpose of grandstands, floors [R1], bridges and vibration-sensitive
facilities worldwide. Due to this research and application of knowledge to
real-world issues and applications, we generated the world's largest
database of operational performance of floors, stadia and footbridges.
Since 2005, we adapted capability for ambient vibration measurements with
applications to `operational modal analysis' and assessment of extreme low
vibration environments [R2]. These unique experimental capabilities have
formed the core that links design, analysis, simulation and evaluation of
performance in commercial (FSDL) projects e.g. for Yorkon and Stoke
Mandeville hospital retrofit.
We developed motion capture and force measurement facilities and used
them to create the world's largest database of ground reaction force and
to develop new models of jumping and walking [R3]. This was necessary to
address deficiencies in the existing human dynamic load models used in
standard design practice. Our research (in collaboration with University
of Manchester) has also provided valuable data on the effects of
perceptible structural vibrations on loads generated by spectators bobbing
on grandstands [R4]. This research was used to validate our contributions
to design guidance, and by FSDL to predict performance for pedestrian and
Based on our research, we created bespoke software, Vibration
Serviceability Assessment Tools (VSATs) [R5], now used by industry in
performance-based design and assessment of footbridges, floors and
grandstands. VSATs links experimentally and numerically derived structural
dynamic properties and applies a range of loading from design guides and
our research is now heavily relied upon by FSDL as a primary tool for
structure serviceability evaluation.
We developed capabilities for remote structural monitoring of
grandstands, long span bridges and buildings incorporating automated
operational modal analysis for the first time in any Civil structure. The
rollout of this technology led to the Tamar Bridge prototype system in
2006, whereby modal property data was broadcast in real time by internet,
and has been used as a prototype for two safety-critical commercial
Most recently in collaboration with University Castilla La Mancha
(Spain), we developed unique capabilities for active vibration control of
floors. The system has been evaluated in service in the office of an
industry partner (WSP) [R6] and featured in subsequent FSDL
proposals for high profile structures.
The criticality of our research is exemplified by our contribution to
interventions to address the type of problems that occurred in the London
Millennium Bridge and regularly occurs in a range of structures that are
rendered unfit for purpose (unserviceable) by lack of understanding of the
source (load) -path (structure) -receiver (use/occupant) chain.
References to the research
[**denotes best indicators of quality of underpinning research]
R1. **Pavic A & Reynolds P (1999). Experimental Assessment of
Vibration Serviceability of Existing Office Floors under Human-Induced
Excitation, Experimental Techniques, Vol. 23, No. 5, 41-45. doi: 10.1111/j.1747-1567.1999.tb01305.x
R2. Brownjohn JMW, Pavic A (2006) `Vibration control of ultra-sensitive
facilities'. Proceedings ICE Structures and Buildings 159, 295-306. doi: 10.1680/stbu.2006.159.5.295
R3. Racic V & Brownjohn JMW (2011) Stochastic model of near periodic
vertical loads due to humans walking. Advanced Engineering Informatics
25(2) 259-275. doi: 10.1016/j.aei.2010.07.004
R4. **Yao S, Wright JR, Pavic A, Reynolds P (2006). Experimental study of
human-induced forces due to jumping on a perceptibly moving structure.
Journal of Sound and Vibration 296(1-2). doi: 10.1016/j.jsv.2006.02.018
R5. **Zivanovic S, Pavic A (2009) Probabilistic modelling of walking
excitation for building floors. ASCE Journal of Performance of Constructed
Facilities 23(1). 132-143. doi: 10.1061/(ASCE)CF.1943-5509.0000005
R6. Reynolds P & Diaz IM, (2010) On-off nonlinear active control of
floor vibration. Mechanical systems and signal processing 24(6)
1711-1726. doi: 10.1016/j.ymssp.2010.02.011
Details of the impact
The impact demonstrated by our activities and research, driven by our
desire to apply our knowledge and exploit our expertise and specialised
equipment, has been primarily achieved through:
- VES engagement with standardisation committees and learned societies
to develop industry guidance (codes and standards) and
- FSDL focusing on commercial activities leading to economic and safety
Impacts on practitioners and professional services: codes and
Our research has contributed to a number of guidance documents/standards.
These are used internationally and have legal status in civil court
actions that can result from poor serviceability.
The Institution of Structural Engineers (2008), "Dynamic
performance requirements for permanent grandstands subject to crowd
action. Recommendations for management, design and
assessment": This is recognised as the international state of the
art (adopted worldwide) and directly applies outcomes of our research
[R1, R4] on stadia performance and human structure interaction.
Structural Engineering Institute, American Society of Civil
Engineers (2013). A State-of-the-Art Report by ASCE SEI Committee on Structural Identification of
Constructed Systems: This presents the measurement technology
developed through our research and an industry application of active
vibration control. Our research [R1, R3, R6] formed one of the six
chapters and one of the 18 case studies.
British Standards Institution (2008) Guide to evaluation of human
exposure to vibration in buildings. Part 1: Vibration sources other
than blasting. (BS6472-1:2008): Our academics are long-term
members of the BSI technical committee, contributing to the development
and establishment of these standards.
The Steel Construction Institute (2009) Design of Floors for
Vibration: A new Approach (Revised Edition, February 2009,
particularly Appendix C): Our research [R1, R4, R5] formed the
basis of the appendix on dynamic testing of building floors.
Economic impacts: Spin-out: Full Scale Dynamics Ltd (FSDL).
Our researchers have been engaged in consulting activities in this field
since 1996. In 2008, due to the large volume of commercial activity, FSDL
was incorporated. No inward investment was sought and cumulative FSDL
turnover to date is around £1m. FSDL is directed by academics and has
seconded six postdoctoral and PhD students to UK and overseas projects,
equipping them with high-level professional skills. Clients include:
- UK companies e.g. Expedition Engineering [S1], Arup, Gifford, Balfour
Beatty, Jacobs, Flint & Neill and Yorkon [S4]
- Overseas clients e.g. Intelligent Engineering (Canada), Seagate (USA)
[S2], Land Transport Authority, (Singapore) and Centroprojekt (Russia)
- National stadium operators such as Premier League/Championship
football clubs (Middlesbrough, Sunderland)
- Public organisations e.g. [text removed for publication] [S3] and
[text removed for publication]
FSDL undertakes and completes approximately 15 high profile projects
annually. The following is a brief digest of the FSDL impact on industry
(economic and safety) grouped by structure type.
Post-Hillsborough, UK football clubs have a legal obligation to ensure
spectator safety, which includes avoiding excessive vibration and
consequent crowd panic. Using the testing, simulation and design tools
developed in our research projects since 1998, FSDL has enabled UK stadia
operators and overseas clients to comply with regulations ensuring safety
and fitness for purpose. As an example, for the London 2012 Olympic
Velodrome [S1] (on behalf of Expedition Engineering, 2009) FSDL used VSATS
and applied the new, at the time untested in practice, stadia design
guidance [R1]. This independent assessment enabled a saving of 400 tonnes
of steel and was essential for the purposes of Category 3 performance
based design compliance due to the inherent low natural frequency of the
"using this approach allowed us to have confidence in a solution which
saved 400 tonnes of steel over using traditional design methods"
"without the involvement of FSDL and the fundamental research
undertaken by your research group..., the dynamic performance of the
lightweight seating deck would have been much more difficult to justify"
In 2011 FSDL applied our research [R1, R2, R5] based ambient vibration
testing technology to identify modal properties and vibration environment
being experienced in the multi-$bn Seagate disk drive production facility
in Singapore (opened 2007). [text removed for publication]. This novel
data collected by FSDL was used to validate modelling of the facility that
had previously been undertaken by VES. These simulations predicted the
behaviour observed and provided the operator with a clear understanding of
how to tackle the problem. Based on Seagate's annual turnover of $12bn and
figures and opinion of the Seagate specialist [S2] annual production loss
of the order $10m appears to have been mitigated by the interventions.
"Brownjohn's vibration work allowed the Seagate engineering staff to
be ahead of the production juggernaut (for once), and not underneath the
"to this day we are still building on Prof. Brownjohn's
original modelling and have made detailed plans for some structural
reinforcements in the specific areas of greatest sensitivity ... we owe
a great debt to this theoretical work apparently all done before one
pile was bored for this building"[S2]
"if production delays are experienced, that if measured in days, would
result in the loss of revenue measured in tens of millions of dollars"
From 2005 we applied our research [R2] based expertise to diagnose and
assess extreme low vibration performance of the foundation systems for the
new Orion high power laser facility at the [text removed for publication].
Successful operation of the £100m facility relies on minute positional
tolerances for multiple laser reflections; our vibration measurements
(conducted 2009) showed these were not exceeded. The facility has now been
successfully commissioned [S3].
In a sequence of R&D projects between 2009 and 2013, FSDL was engaged
by Yorkon, the leading UK off-site construction specialist, to apply
research [e.g. R1, R3, R4, R5] and resolve a key problem of liveliness of
their ultra-light building flooring systems under pedestrian-induced
dynamic loading. As a result of this 4-year work, Yorkon's new Pioneer
modular building system was developed featuring an order of magnitude
lower dynamic responses of its floors. This was achieved by discovering
and exploiting the beneficial effects of the novel pre-installed
lightweight concrete floor and vertical partitions. With the Pioneer
system, Yorkon moved decisively into quality public buildings market, such
as schools and hospitals. After investing [text removed for publication]
into this R&D, a significant proportion of Portakabin Group annual
sales (£30m) are now featuring the Pioneer flooring [S4].
In 2008, the flue gas exhaust stack (chimney) at Rugeley Power Station
was suffering enhanced vortex shedding due to up-wind construction of a
replacement chimney. As the wind-induced sway (predicted by the operator)
could have resulted in structural failure and collapse, FSDL were
commissioned to monitor the performance of the old chimney and its tuned
mass damper. The damper was designed by Multitech (France) to reduce the
vibration to levels that would not compromise operation of the power
station. Remote monitoring technology developed in our research on the
Tamar Bridge study was adapted to track the performance of the
chimney/damper system to the power station staff in real time. The
monitoring system clearly demonstrated that the damper worked and removed
any safety concerns [S5]. Since 2009, FSDL has operated a more
sophisticated monitoring system on a chimney at the Sellafield Nuclear
facility. The system enables the site operator to comply with stringent
safety requirements avoiding the need to interrupt site operation.
Sources to corroborate the impact
S1. Letter from Director of Expedition Engineering corroborating impact
of our intervention and the subsequent economic benefit.
S2. Letter from Sr. Staff Engineer at Seagate Technology corroborates
impact of our research to resolve vibration related disturbance of high
value manufacturing and economic benefit.
S3. [text removed for publication].
S4. Letter from Principal Engineer at Yorkon (Portakabin Ltd)
corroborating the application of our research and the financial impact
associated with our activities.
S5. Chief Engineer at Bierrum International can corroborate the
implementation of our monitoring system and the safety and on-going
operation at Rugeley power station.