June 2016
TheStructuralEngineer
Volume 94 | Issue 6
The flagship publication of The Institution n of Structural Structu Engineers
NON�INVASIVE APPRAISAL OF HISTORIC STRUCTURES PROFILE: ANNE FULLER PARTIAL DEFENCES TO PI CLAIMS PLATES AND SHELLS: AN ERROR IN TIMOSHENKO’S TEXT FEMALE�FRIENDLY WORKPLACES?
WHEEL OF FORTUNE The award-winning design de sign of the world’ world’s s largest observation wheel in Las Vegas
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Contents
PAGE 30 PARTIAL 30 PARTIAL DEFENCES TO PI CLAIMS
TheStructuralEngineer June 2016
PAGE 40 NON-INVASIVE 40 NON-INVASIVE STRUCTURAL APPRAISAL
3
PAGE 52 INSPIRING 52 INSPIRING THE NEXT GENERATION
TheStructuralEngineer Volume 94 | Issue 6
Upfront
Professional Profe ssional guidance gui dance
5
Editorial
30
6
Institution news:
Engineer ’s Guide to PI Claims. Part Engineer’s Part 5: Defence arguments – partial defences
32
Managing Health & Safety Risks No. 51: 51: Hazards from gas
34
Confidential Reporting on Structural Safety (CROSS)
Institution AGM notice Benevolent Fund AGM notice 8
Institution news: Are we giving you what you want?
10
Institution news: Do you know your Husband Prize from your Oscar Faber Award?
Features 14
36
Getting nostalgic about the future for wood
Project focus 22
Technical 40
An error in Timoshenko’s “Theory of Plates and Shells” Conservation compendium. Part 18: Non-invasive quantitative appraisal of historic floor structures
The Vegas Vegas High Roller observation wheel
Opinion 46
Profile: Anne Fuller
48
Viewpoint: What do women want?
50
Conservation compendium. Epilogue: The future of conservation conservatio n engineering
52
Viewpoint: Inspiring the next generation
55
Verulam
At the the back 58
Diary dates
59
Spotlight on Structures
60
And finally…
61
Products & Services
63
Services Directory
64 TheStructuralEngineerJobs
Front cover: ©Getty cover: ©Getty The Structural Engineer P�ESIDENT Alan Crossman CEng, FIStructE, FICE, MCIWEM CHIEF EXECUTIVE Martin Powell EDITO�IAL HEAD OF PUBLISHING Lee Baldwin MANAGING EDITOR Robin Jones t: +44 (0) 20 7201 9822 e:
[email protected] org EDITO�IAL ASSISTANT Ian Farmer t: +44 (0) 20 7201 9121 e: ian.farmer@istruc
[email protected] te.org
www.thestructuralengineer www.th estructuralengineer.org .org ADVE�TISING
EDITO�IAL ADVISO�Y G�OUP
DISPLAY SALES Patrick Lynn t: +44 (0) 20 7880 7614 e:
[email protected] [email protected] o.uk
Will Arnold MIStructE Allan Mann FIStructE Don McQuillan FIStructE McQuillan FIStructE Chris O’Regan FIStructE O’Regan FIStructE Angus Palmer MIStructE Simon Pitchers MIStructE
�EC�UITMENT SALES Paul Wade t: +44 (0) 20 7880 6212 e: paul.w
[email protected] [email protected] o.uk DESIGN SENIO� DESIGNE� Craig Bowyer C�EATIVE DI�ECTO� Mark Parry P�ODUCTION P�ODUCTION EXECUTIVE �achel Young
Price (2016 subscription) Institutional: £390 (12 issues i ncl. e-archive, p&p and VAT) Personal: £125 (12 issues incl. p&p) Personal (Student Member): £40 (12 issues incl. p&p) Single copies: £35 (incl. p&p) Printed by Warners Midlands plc The Maltings, Manor Lane Bourne, Lincolnshire PE10 9PH United Kingdom
© The Institution of Structural Engineers. All non-member authors are required to sign the Institution’s ‘Licence to publish’ form. Authors who are members of the Institution meet our requirements under the Institution’s �egulation 10.2 and therefore do not need to sign the ‘Licence to publish’ form. Copyright for the layout and design of articles resides with the Institution while the copyright of the material remains with the author(s). All material published in The Structural Engineer carries carries the copyright of the Institution, but the intellectual rights of the authors are acknowledged. The Institution of Structural Engineers International HQ 47–58 Bastwick Street London EC1V 3PS United Kingdom t: +44 (0)20 7235 4535 e:
[email protected] The Institution of Structural Engineers Incorporated by �oyal Charter Charity �egistered in England and Wales number 233392 and in Scotland number SC038263
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Upfront
TheStructuralEngineer
Editorial
June 2016
5
Upfront Appealing to Ap everyone Robin Jones Managing Editor
What makes engineering – and structural engineering in particular – an attractive career choice? And why is it less so for women? With 23 June marking National Women in Engineering Day in the UK, Margaret Cooke, director of a firm where 50% of the technical staff are female, draws on her own experience to consider what makes a practice appealing to women (page 48). 48). While recognising that (as a generalisation) there are differences in approaches between men and women, she concludes that young engineers – whether male or female – are motivated by the same things: interesting work, training, career prospects and remuneration. However, as their careers progress, flexibility becomes increasingly important for women. Margaret’s views are echoed by Anne Fuller, the subject of this month’s Profile (page 46), 46), who also sees flexible working as a key factor. In Anne’s words, “We need to change construction to be a better place for everyone; when that happens it will automatically be a place for women to want to work.” While increasing the number of women who enter – and remain in – the profession is one way to close the skills gap in the UK, another is to encourage young people from a wider range of backgrounds to do likewise. In our other Viewpoint this month, three young engineers from AKT II describe a project to introduce students at a London sixth-form college to structural engineering (page 52). 52). This month also sees the end of the Conservation compendium, with the final article in the series looking at non-invasive appraisal of historic structures (page 40). 40). While author, Jon Avent, focuses principally on floor structures, the techniques discussed can be
The Structural Engineer provides structural engineers and related professionals worldwide with technical information on practice, design, development, education and training associated with the profession of structural engineering, and offers a forum for discussion on these matters promotes the learned society role of the Institution by publishing peer-reviewed content which advances the science and art of structural engineering provides members and non-members worldwide with Institution and industry related news provides a medium for relevant advertising
used for a range of applications. James Miller then wraps things up (page 50) by 50) by looking back over topics covered and encouraging those working with historic structures to consider becoming accredited with the Conservation Accreditation Register for Engineers (CARE). We hope you have found the series informative and that it remains a useful resource in The Structural Engineer online online archive. Elsewhere, in the Upfront section, we summarise the results from our reader survey (page 8). 8). By and large, you seem to be pleased with what The Structural Engineer offers; offers; our intention is to use the results to build on that offering to ensure that the magazine continues to be relevant to members. With the Institution’s annual People and Papers Awards coming up on 8 June, we also offer a brief guide to the “papers” side of things (page 10). 10). This potential for recognition is a great reason to submit an article to The Structural Engineer or or entry to one of the other awards. In Features, we consider the potential of engineered timber from an unusual perspective: Metsä Wood’s “Plan B” is a reimagining of iconic structures from the past using this sustainable material (page 14). 14). In Project focus, authors from Arup describe the design of The Vegas High Roller – the world’s largest observation wheel (page 22). 22). In Professional guidance, guida nce, the series from f rom Griffiths & Armour moves on from last month’s article about complete defences to examine partial defences to professional indemnity claims (page 30). 30). In Technical, Angus Ramsay and Edward Maunder bring to light an error in Timoshenko’s Theory of Plates and Shells and discuss its significance to the practising engineer (page engineer (page 36). 36).
The Institution has over 27 000 members in over 100 countries around the world is the only qualifying body in the world concerned solely with the theory and practice of structural engineering through its Chartered members is an internationally recognised source of expertise and information concerning all issues that involve structural engineering and public safety within the built environment supports and protects the profession of structural engineering by upholding professional standards and to act as an international voice on behalf of structural engineers
The Structural (ISSN Engineer (ISSN 1466-5123) is published 12 times a year by IStructE Ltd, a wholly owned subsidiary of The Institution of Structural Engineers. It is available both in print and online.
Contributions published in The Structural Engineer are published on the understanding that the author/s is/are solely responsible for the statements made, for the opinions expressed and/or for the accuracy of the contents. Publication does not imply that any statement or opinion expressed by the author/s reflects the views of the Institution of Structural Engineers’ Board; Council; committees; members or employees. No liability is accepted by such persons or by the Institution for any loss or damage, whether caused through reliance on any statement, opinion or omission (textual or otherwise) in The Structural Engineer , or otherwise.
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TheStructuralEngineer
Upfront
June 2016
Institution news
Institution AGM
Benevolent Fund AGM
Notice is hereby given that the 107th Annual General Meeting of the Institution of Structural Engineers will be held at 47–58 Bastwick Street, London EC1V 3PS, United Kingdom, on Thursday 21 July 2016 at 4:00pm for the t ransaction, by Voting Members, of the business set out below.
Notice is hereby given that the 21st Annual General Meeting of members will be held at 47–58 Bastwick Street, London EC1V 3PS, United Kingdom on Thursday 21 July 2016 at 4:15pm (or immediately following the conclusion of the Annual General Meeting of The Institution of Structural Engineers at 4:00pm) for the transaction of the business set out below.
1)
To read the notice convening the meeting.
2)
To read, read, confirm and sign the minutes of the 106th Annual General Meeting held on 23 July 2015 (published in The Structural Engineer , September 2015).
1)
To read the notice convening the meeting.
3)
To receive receive the financial statements and balance sheet for the year 2015, together with the auditors’ report thereon, and the report of the Board for 2015.
2)
To read, confirm and sign the minutes of the 2015 Annual General Meeting (published in The Structural Engineer , September 2015).
To appoint auditors for the ensuing year and to fix their remuneration. remuneration. (The Board recommends BDO LLP, chartered accountants and registered auditors, at a fee to be agreed w ith them by the Board.)
3)
To receive and, if thought fit, to adopt the financial statements, the directors’ and trustees’ report and the auditors’ report for the year ended 31 December 2015.
4)
To appoint auditors for the ensuing year and to fix their remuneration. (The trustees recommend BDO LLP, chartered accountants and registered auditors, at a fee to be agreed with them by the trustees.)
5)
To appoint trustees. (Mr J M Allen and Mr J D Parsons retire as trustees by rotation and offer themselves for reappointment. The trustees recommend the appointment as from 22 July 2016 of Mr N Westwood, who is willing to be appointed, in place of Mr S M Craddy whose resignation will take effect upon the conclusion of the meeting.)
4)
5)
To consider and, if thought thought fit, to adopt the following motion:
THAT, in accordance w ith the provisions of Regulation 3.1, and in confirmation THAT of proposals of the Board, annual subscriptions with effect from 1 January 2017, and until otherwise determined, shall be: Fellow Member, Associate Associate-Member Technician Member Graduate, Companion, Student (working)
£405 £318 £208 £161 £156
By order of the Board D M POWELL Chief Executive
1 June 2016
5.7..1 defines ‘Voting Member’ as a Explanatory Note 1 – Regulation 5.7 Chartered or an Incorporated Structural E ngineer or a Technician Member or a Graduate whose subscription and other membership payments have been paid. Explanatory Note 2 – The financial statements and balance sheet, the auditors’ report and the report of the Board are on t he website (www.istructe. org/about-us/ org/ about-us/governance/ governance/annual-report-and-accounts); annual-report-and-accounts); copies may be obtained on application to the Chief Executive at the Institution of Structural Engineers, 47–58 47–58 Bastwick Street, London EC1V 3PS Explanatory Note 3 – Under Regulation 5.8, unless a poll is demanded, a motion put to the vote of the meeting shall be decided on a show of hands by a majority of the Voting Members present in person and voting. Explanatory Note 4 – In accordance with Regulation 5.3, only the business specified in this notice may be considered at the meeting. Explanatory Note 5 – The rates of subscription paid by retired members are set by the Board under Regulation 3. 5. The rates for 2017 will be: Retired Fellow with The Structural Engineer £82; £82; Retired other grades with The £68, Retired without The Structural Engineer £36. £36. Structural Engineer £68,
Charity registered in England & Wales number 233392 and in Scotland number SC038263
By order of the trustees DR S M DORAN BSc Eng AKC PhD CEng MICE ACIS Secretary 1 June 2016
Note 1 – The 2015 report and accounts are on the website (www.istructe.org/about_institution/Documents/ benannualreport.pdf) or copies may be obtained on application to the Secretary, The Institution of Structural Engineers Benevolent Fund, 47–58 Bastwick Street, London EC1V 3PS, United Kingdom. Note 2 – A member of the Benevolent Fund has a statutory right to appoint another person as their proxy to exercise all their rights to attend and to speak and vote at the Annual General Meeting. A form of proxy may be obtained from the website (web address in Note 1) or on application to the Secretary (postal address in Note 1).
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TheStructuralEngineer
Upfront
June 2016
Institution news
Are we giving you Ar wh w hat you want? We received a terrific response to The Structural Engineer 2016 2016 reader survey, with 1614 1614 of of you taking the time to complete the questionnaire. Respondents reflected the diverse membership of the Institution: 68% were based in the UK and UK and 32% outside the UK; UK; the largest categories were Chartered Members (34%), (34%), Graduate Members (29%) and (29%) and Student Members (12%). (12%). Here’s what you told us…
READING HABITS
How often do you read it?
How do you read The Structural Engineer ?
3.50%
%
3
0
6
.
1
In print
Online
50.25%
21.93% 2 7 . 0 0
Every issue Most issues Ocacasionally Rarely
I don’t read it
24.23%
3.59%
3
.
5
%
Both
%
7
4
"THE STRUCTURAL ENGINEER IS AN EXCELLENT PUBLICATION AND THE ONLY PUBLICATION I READ FROM COVER TO COVER"
How long do you spend reading each issue?
23.88% Less than 30 mins
8%
Reduced members’ rates on technical publications
48.60% 30 mins to 1 hour
19.53% 1–2 hours
12% 12 %
Access to extensi ex tensi ve Li brar y col lect ion, subject knowledge of Library staff and use of enquiry/loans service
7.98% 2+ hours
17% 17 %
Access to gl obal, nati onal and r egion al engineering communities via events, courses and online services
www.thestructuralengineer.org
9
"I LOVE THE PROFESSIONAL GUIDANCE AND TECHNICAL SECTIONS SECTI ONS – MORE OF THE T HE SAME PLEASE"
QUALITY OF CONTENT
Overall rating 0.57%
3.41%
Value Val ue of o f each ea ch sect section ion 2 5 % 2 7 .
9
1
Technical 1 6%
. 9 92 %
17%
Professional guidance 1 7%
Excellent Very good Good Average Poor
Project focus 1 Verulam
22%
3
38% 37%
18%
13%
30%
40% 20%
14% 25%
39%
11%
Industry news 2
30%
35% 22%
Features 1
38% 40%
11%
Spotlight on Structures 2
5 0 38 %
38%
10%
40% 42%
9% 29%
8%
.
Opinion (excl. Verulam)
2
Institution news
2
Diary dates
ONLINE
How often do you access the online archive?
22%
42% 31%
42%
9%
35%
Of no value at all
7%
26% 19% 35%
Of some value
7%
Valuable
6%
17%
Very valuable
4%
Extremely valuable
CAREERS
At least once a week
If you were looking for a new job, which publications or related job boards would you cons consult? ult?
26% At least once a month
22% Publication
At least once every three months
Job board
30%
The Structural Engineer
Less often
New Civil Engineer
15%
Construction News The Engineer
Never
Building %
% % % % % 4 2 2 8 1 3 1 2 9
6 4 3 1 3 1 7
How would you like to read online The Structural Engineer online
%
VALUE TO INSTITUTI INS TITUTION ON MEMBERS MEMB ERS
PDF
67%
4 % % 1 %
The Structural Engineer …
Full-text web page Tablet app
1 4%
Phone app I wouldn't read it online
20%
45%
30%
…is my preferred engineering publication
13
18%
53%
26%
…enhances the Institution’s image
26% 22%
21%
20%
12
14%
58%
24%
54%
24%
57%
20%
…is well designed
12
18%
…adds value to my membership
1 3
Most valuable member benefit
28% 28 %
Career and professional development opportunities
18%
…contains valuable information that helps my career
35% 35 %
The Struc tural Engin eer
Strongly disagree
Disagree
Indifferent
Agree
Strongly agree
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TheStructuralEngineer
Upfront
June 2016
Papers Awards
Do you know your Husband Prize from your Oscar Faber Award? With the Institution’s Institution’s annual People and Papers Awards Luncheon taking place on 8 June, we offer a brief guide to the Papers Awards – and the presidents they are named after. Awards are made annually at the discretion of the Papers Awards Awards Judging Panel.
Murray Buxton Award An award to the author(s) of a paper of general interest that has been published in The Structural Engineer . A Murray Buxton Award may take the form of a Medal or a Diploma and one or more of each may be given each session. The award is not restricted to members of the Institution. Captain Murray Buxton MC
Derrington Construction Award An award to the author(s) of a paper deemed to refer to construction and/or health and safety that has been published in The Structural Engineer . The Derrington Construction Award may take the form of a Medal or Diploma and one or more of each may be given each session. The award is not restricted to members of the Institution.
John Derrington 1921–2008 President: 1979–80
John Derrington was the first civil engineering contractor to be elected Institution President, having spent his entire working life with Sir Robert McAlpine & Sons. He had a great concern for health and safety and was the first President of The Concrete Society.
1889–1940 President: 1940
A former missionary, Murray Buxton was awarded the Military Cross for rescuing his troops in full view of the enemy at Gaza during World War I. Early in his term as Institution President he was killed during an air raid in London, along with one of his three brothers.
Guthrie Brown Award A commemorative Medal awarded to the author of a paper published in The Structural Engineer who is both a member of the Institution and not more than 40 years of age. Papers prepared under joint authorship are eligible, provided that all authors are members of the Institution and none is more than 40 years of age. John Guthrie Brown 1892–1976 President:1956–57 Gold Medallist: 1964
As a senior partner of Sir Alexander Gibb, John Guthrie Brown specialised in hydroelectric engineering and was the first British engineer to be President of the International Commission on Large Dams (ICOLD).
Husband Prize A prize for merit to the author(s) of a paper relating to bridges that has been published in The Structural Engineer . The prize is not restricted to members of the Institution.
Prof. Joseph Husband 1872–1962 President:1937–38
Joseph Husband established the Engineering Department at the University Univers ity of Sheffield, which he headed for fo r over 40 years. He set up the consultancy Husband & Co, of which his son and later fellow Institution President, Charles, became a senior partner.
Clancy Prize A prize for merit to the author(s) of a paper published in The Structural Engineer which which advances the understanding and practice of the whole-life management of structures. This includes surveys, investigations, strategic planning, testing and subsequent works to the structure. For a paper to be eligible, at least one author must be a member of the Institution.
Brian Clancy 1940– President: 1996–97
Brian Clancy is a consulting engineer, advocate of members getting involved with their regional group and the driving force behind the Institution’s publications on Subsidence of low-rise buildings and Guide to surveys and inspections of buildings and associated structures.
www.thestructuralengineer.org 11
Os c ar F ab e r A w ar d
Kenneth Severn Award
Sir Arnold Waters Medal
An award to the author(s) of a presentation that has been made at an Ordinary Meeting or Colloquium of the Institution. An Oscar Faber Award may take the form of a Medal or a Diploma and one or more of each may be given each session. The award is not restricted to members of the Institution.
An annual essay competition for authors under the age of 28 in which the subject is set by the incoming President. President. It is open to both members and non-members of the Institution. The Kenneth Severn Award takes the form of a Diploma and carries a prize of £500. The winning essay is considered for publication in The Structural Engineer .
An award to an author, who is a member of the Institution, of a presentation of merit which has won a regional group prize. The Medal may be awarded jointly where there is more than one author of a presentation, provided each is a member of the Institution; or may be shared when presentations are adjudged to be of equal merit. To be eligible, presentations must be submitted to HQ by the regional group.
Oscar Faber CBE
Kenneth Severn
1886–1956
1918–2004
Sir Arnold Waters VC
President: 1935–36
President: 1972–73
1886–1981
Oscar Faber developed the early theory and practice of reinforced-concrete design – his “plastic yield” theory was a forerunner to limit state design. Faber’s best known structure is the rebuilt Bank of England and he received a CBE for his work on the rebuilding of the House of Commons.
A former Captain in the Royal Engineers, Kenneth Severn had an international reputation as an arbitrator and was an advocate of the importance of education and training. The Technician Education Council was founded in 1973 during his term as President, the Institution having introduced its Technician Certificate Scheme in 1970.
President: 1933–34 and
1943–44
The only person to have been Institution President twice, Sir Arnold Waters was awarded the Victoria Cross for an act of bravery in completing the construction of a bridge during the second Battle of the Sambre near Ors in France in 1918.
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TheStructuralEngineer June 2016
13
Features Articles with a broad scope often accompanying a significant Institution award or event.
14 Getting nostalgic about the future for wood Matt Collins, Sales Director at Metsä Wood, explains why the engineered timber specialist's "reimagining" of some iconic buildings from the past – its Plan B programme – has resonated so strongly with the contemporary design community, as well as the reasons high-performance, sustainable, engineered timber systems are increasing their share of the construction market.
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TheStructuralEngineer June 2016
Feature Timber future
Getting nostalgic about the future for wood Matt Collins Sales Director, Metsä Wood
Introduction
It is a characteris characteristic tic of mankind that we are fascinated by the lives of our ancestors, right back to the times of the early cave dwellers and hunter-gather hunter-gatherers. ers. Archaeologists Archaeologis ts research what they ate and wore, as well as the tools they made and the shelters which prehistoric man fashioned from the materials available. Museums across the globe are full of fascinating artefacts, but often of even greater interest are the early structures that remain: famous heritage sites such as the Colosseum in Rome. Tourists Tourists visit the ruins in their thousands throughout the year, listening to guides recounting stories of how the gladiators fought to entertain the crowds, and wondering at the scale of the place. Archaeologists Archaeologist s and academics are also keen to rediscover the skills of the ancients – from “knapping” flints to firing pots – but suppose we wanted to look again at the way they had set about their most iconic building projects; or even consider ways of providing a modern interpretation. The challenge of reimagining these great structures from the past, reengineered to take advantage of today’s most advanced and sustainable building systems, is the task that has been set for some internationally renowned design professionals by Metsä Wood, an international timber engineering specialist. Historians have expended a lot of time and energy pondering how ancient structures such as the pyramids and Stonehenge were built, without the use of cranes or other heavy lifting and cutting equipment. Through its project named “Plan B”, Metsä Wood has now enabled these consultants to explore how three very different edifices might have been improved upon, with more to come. To share these fresh insights into how these wonders – wrought from stone and then steel – could be redesigned and enhanced thanks to modern timber
1 Figure Dimensions of Colosseum
"The decision was taken to base the redesign on the use of LVL " technologies, Metsä Wood has made the visualisations available through a new microsite 1. It gives access to plans and technical information, stretching from the original concepts through to 3D models. Colosseum
As one of the most recognisable ruins remaining from the time of the Romans, the Colosseum is both vast (Figure vast (Figure 1) and 1) and the subject of interest from historians conjecturing over the way the spaces functioned; and aspects such as what sort of roof or canopy it might have featured. The Plan B project team elected to work with Antti Laiho from Finnish-based Helin & Co Architects to try and create a
contemporary visualisation of how it might contemporary look and function if it had been built using modern timber systems. In essence: to produce a recognisable replacement, which relies on wood as its main raw material rather than stone. Also emphasising the reduction of waste and compressing the construction time required, as well as cutting overall cost, the decision was taken to base the redesign on the use of laminated veneered lumber (LVL) for the columns and beams. This product is not only highly sustainable, but offers great load-carrying capacity: providing tensile and torsional strength in addition to compressive strength. The process was started by utilising a satellite image of the Colosseum to pinpoint all of the salient details on a scaled grid of the site. More information was also abstracted from existing cross-sections and detail drawings of the various elements. The next step was to identify relevant loading values for the structure and the crowds which massed there during events, in order to complete a proper structural analysis upon which new designs could be based.
www.thestructuralengineer.org 15
2 �Figure Load-bearing capacity of columns a) Calculated load
b) Maximum load
3 Figure Proposed structure
The design team assumed that people would be packed onto the terraces and other viewing areas at a density of four persons per square metre: taken as an equivalent load of 400kg or 4kN/m2. An additional 2kN was calculated for the structure itself: relating to a 7m span beam typically weighing 500kg, plus the floor elements, at 1000kg each. The new timber columns, at 15m in height, would weigh some 3t. A maintenance load of 0.4kN was added to the dead load and, along with the relevant spans or other dimensions, input into AutoCAD; while the designers further made use of Finnwood and Tekla software. The LVL elements were, not surprisingly, shown to be well able to accommoda accommodate te such load conditions (Figure 2) – 2) – being at some 60% of the ultimate limit state – and it was the need to control low-frequency vibration in the structure which dictated many of the beam sizes. The Finnish standard adopted set a maximum frequency of 9Hz. The maximum
deflection allowed was 0.5mm for a load of 1kN at the centre of span. Antti Laiho asserted: “At 190m by 158m, the Colosseum is a huge building – almost three times the size of an average sports arena. Initially,, I thought that wooden construction to Initially such an extent wouldn’t be feasible in reality. As the project proceeded, I changed my mind. It would not only be possible, but easy as well.” The architect worked with Metsä Wood’s structural engineer, engineer, Jussi Bjorman, to produce a new structural solution employing various LVL products in order to recreate the Colosseum’s distinctive elliptical form, as well as its arrangement of columns, arches and beams (Figures 3 and 4). 4). Crucially though, the off-site fabricated laminated elements would be erected far faster and more costeffectively effective ly than the large masonry vaults (Figure 5). 5). Interestingly, the concept of substituting LVL LV L for massive masonry forms would not
only allow larger spans while maintaining such physical qualities as load-bearing capacity and fire resistance, but it would also create 12% additional space in the vaults below the seating arena. This could, for example example,, now potentially accommodate accommodate VIP facilitie facilities s and retail outlets. It is also certain that health-andsafety standards would be unrecognisabl unrecognisable e from the workplace of 72 AD.
Empire State Building After the success of the Colosseum exercise, exercise, Metsä Wood identified a truly outstanding 20th-century property to be given the Plan B treatment. Some of the film footage that survives of erecting the Empire State Building back in the late 1920s (it was completed in 1931) is hairraising in its own right, with the spider-men stepping from one moving girder to another, hundreds of feet above the street. Almost a century ago, the construction method was viewed as dynamic and cost-
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June 2016
Timber future
a) Inclined terrace–beam connections
6 Figure Section of Empire State Building reimagined in timber
b) Main beam–column connections
4 �Figure Proposed connections
5 �Figure Construction schedule
a) One month
b) Six months
effective. For this reimagination, Metsä Wood recruited Michael Green of architects MGA and timber specialist, Equilibrium Consulting, to determine if it could stand just as tall in LVL (Figure 6); 6); while also exploring other aspects of the Manhattan skyscraper’s skyscraper’s specification (Figure 7). 7). Once again, the expert use of modern structural analytical techniques and the different software packages enabled the highly experienced project team to extrac extractt
the ultimate in potential from LVL: optimising section sizes, reducing weight compared to the hot-rolled steel I-beams of 80 years ago, and accelerating the programme times. Michael Green confirmed: “I believe that the future belongs to tall wooden buildings. Significant advancements in engineered wood and mass timber products have created a new vision for what is possible for safe, tall, urban wood buildings. The challenge now is to change society’s perception of what’s
possible.” Significantly,, the third building in the Plan B Significantly series is the seat of the German parliament, the Reichstag, where much of the debate concerns environmental legislation. This project has involved FH Finnholz, a leading German construction company, company, and its engineer,, Andreas Rutschmann; with the engineer iconic domed roof offering one of the main technical challenges. So, how do the Plan B reimaginings of the
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7 �Figure Detail of timber columns, beams and floor
Empire State Building and other structures resonate with and empower the architects and engineers confronted by the challenges set by today’s client aspirations, codes of practice,, price constraint practice constraints s and other issues? Modern methods of construction
It is now widely accepted, including in government circles, that modern methods of construction, and especially off-site fabrication, fabricatio n, are crucial to the UK building sector increasing its capacity; and being able to meet such challenges as providing sufficient housing housin g to accommodate a rapidly rapidl y growing population. Compared to traditional construction methods, factory fabrication offers many advantages, with the workforce having dry and comfortable conditions which help achieve higher productivity levels; while they are also far less at risk of accident or injury. Their output is also acknowledged as being of a higher quality, while what is often a repetitive repetiti ve and highly mechanised process is also much more accurate. Importantly, off-site manufacturing is helping to offset the constraints affecting affecting the wider construction market, caused by the shortage of traditional skills after the recession. Although off-site takes many forms, timber-based timber-ba sed systems dominate in terms
of both volume and value within residential development, where the big housebuilders are at last coming to understand the full benefits. In other sectors also – such as education, commercial, retail and hospitals – engineered timber is increasing its market share, and being seen as the sustainable answer. Unlike steel, aluminium and cement- or concrete-based concrete-b ased alternatives, engineered timber systems involve very low embodied energy within their production cycles. In the case of LVL, not only does the majority of the raw material come from sustainable, wellmanaged forests offering a fully certified and traceable chain of custody, but also where slow-grown timber from northern latitudes is employed, it provides enhanced strength and durability. The ultra-slim sections of timber which go to make up the various laminated veneered
"Load-bearing capacity far exceeds that of solid timber"
elements that comprise each structure lock in carbon for the life of the building and beyond, while providing totally predictable performance. With sawn timber timber,, disconformities such as knots, shakes and splits represent weaknesses, and can compromise the overall performance of a section. For the production of LVL, the round wood is cut into 3mm laminates and exposed to detailed automated examination examination so that unsuitable material is rejected. The laminates are then re-oriented and glued before being subjected to high pressure; forming a composite where the effect of knots and other irregulariti irregularities es is greatly reduced. The resulting load-bearing capacity far exceeds exce eds that of solid s olid timber beams and columns, while such problems as dimensional stability and susceptibility to moisture are ruled out. Structural engineers are therefore able to design even multistore multistorey y properties, knowing exactly how every element or component will behave. For instance, the shrinkage that affects traditional timber frames, and that typically discouraged designers from considering them for buildings of more than four to five storeys, is much less of a concern. The fire resistance of engineered timber structures is also noticeably superior to that of traditional timber-frame methods, making them far safer; not just during the service life of a building, but also during the v ulnerable build phase. The multi-layer multi-layered ed but essentially homogenous make up of LVL offers heat and flames far fewer surface striations to attack, and this limits the charring rate for the material to just 0.7mm per minute. In the absence of any other source of fire or accelerants, LVL will tend to self-extinguish, with very limited tendency for the surface spread of flame. The designer is therefo therefore re at liberty to expose and express the elegance of the timber structure and the beauty of the wood itself, rather than rushing to protect it with fire boarding or heavy, sprayed intumescent coatings as they would in the case of sawn timber,, or even steelwork. This resistance to timber fire is effectively endorsed by the extensive use of LVL and cross-laminated timber (CLT) for education projects across the UK. The many advantages of LVL for forming complex arrangements arrangements of columns and beams – including flexibility of design and buildability – can be continued on through the building, with the engineered timber manufacturing manufacturi ng industry also producing advanced solutions for both walling and flooring applications.
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Feature Timber future
represents a truly holistic advancement for the future of construction and a process to which leading manufacturers are fully committed. committe d. In the production process, BIM facilitates facilita tes the generation of precise cutting schedules and reducing waste, while the technology has also been shown to help avoid “clashes”” between, for instance, structural “clashes components and building services. Accordingly Accordingl y recognised for the proven benefits of sustainable production based on well-managed sources – with certified chain of custody – state-of state-of-the-art -the-art design support and innovative manufacturing techniques delivering high-quality components on schedule, engineered timber systems have earned inclusion for some of the most architecturally acclaimed projects of recent times.
Figure 8 Metropol Parasol, Seville
Metropol Parasol
These similarly combine the benefits of responsibly produced timber as an environmentally environment ally friendly raw material, with those of factory prefabrication, prefabrication, to enhance the build process. Their quality and dimensional accuracy can further facilitat facilitate e the completion of a much more airtight, fabric-first building envelope which is far less reliant on the post-erection installation of tapes, membranes and mastic sealants. Therefore, Therefor e, the energy performance of both domestic and non-domestic properties can be brought down to within the parameters of the Passivhaus standard or other near-tozero carbon designs.
BIM While in the UK the government is widely regarded to be driving the agenda for the uptake of Building Information Modelling
(BIM) due to making its use mandatory at Level 2 for new public sector projects, many manufacturers manufactur ers who operate abroad had embraced the technology some years ago. Specifiers will therefore be pleased to know that most contemporary engineered timber components and systems are available to download as BIM components or objects. Importantly,, BIM not only has the potential Importantly to inform the design process and make manufacture more mo re efficient, it can c an also radically influence construction management, project management and cost control. This, in sequence, stretches right through to the future facilities management of properties, making them far more economic to operate and own throughout the lifetime of the building. Properly incorporated into the design, manufacture manufactur e and erection process, BIM
The iconic Metropol Parasol in Seville (Figure 8) represents 8) represents one of the largest timber constructions in the world and also happens to be one of the most sustainable – manufactured manufactur ed using a 100% traceable wood value chain, from sapling to product. Constructed from 3400 individual timber elements and employing 3000 load-bearing connection nodes, the structure creates an urban space within the medieval inner city of Seville. Its stunning, curving and twisting parasols feature wood elements of up to 16.5m in length, with thicknesses ranging from 68–311mm; protecting the people under it from the often fierce heat of the sun over the city. According to the German architect Jürgen Mayer H. who designed it, “Metropol Parasol has ‘revitalised’ the Plaza de la Encarnación to become the new, contemporary urban centre. Its role as a unique urban space within the dense fabric allows for a great variety of activities, such as history, leisure and commerce.. Its highly developed infrastructure commerce has fashioned the square into an attractive destination for tourists and locals alike.” The Metropol Parasol additionally houses an archaeological museum, a farmers’ market, an elevated plaza, multiple bars and restaurants restauran ts both beneath and inside the parasols – or “mushrooms” as some have described them. Plus, there is as a panoramic terrace on the very top of the four floors, accessed via the “stems” to the mushrooms which contain stairs and lifts. Comprising six parasols, the design was inspired by the vaults of the city’s cathedral and the ficus trees in the nearby Plaza de Cristo de Burgos – indeed, the structure is organic in appearance, projecting a sense of fluidity and movement. The whole structure is approxim approximately ately 50m long, 75m wide and 28m high. As with other
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free-flowing, organic designs that have been free-flowing, created elsewhere using engineered timber solutions, the individual elements – in this case formed from LVL – have been arranged in an orthogonal grid pattern (Figure 9). 9). The architect confirmed that only an engineered timber system would be suitable for the construction of such large and complex structures as the Metropol Parasol due to its excellent strength-to-weight ratio. LVL in particular is proven as an incredibly strong, yet light and ultimately versatile building material. For For the parasols, a plant in Germany produced a total volume of approx. 2500m3 of parallel LVL. Then the wooden structure was covered by two-component polyurethane varnish to protect the elements against the weather. The design process was further facilitated through the intense electronic exchange exchange of data between all parties in the planning process as an essential element to the structure’s development and construction. The data generated by the architectural model was directly integrated into the programs of the engineer, Arup, and the construction company. Conclusion
Wood was prehistoric man’s most accessible, flexible and plentiful building material, with the strength to create defensible structures as well as rudimentary shelters. Looking back over the UK and the world’s built environment, the material is also very widely and articulately represented as a key element to some of the most striking buildings: from the magnificent hammerbeam roof of Westminster Hall to some of the present day’s most inspired architectural architectural creations. We have also seen within the scope of this article how contemporary timber technology could be employed to re-engineer and even improve upon iconic buildings from history. For timber is not only a highly aesthetic and
9 �Figure Orthogonal grid pattern of structure
sustainable raw material that is constantly being replanted and regenerated, but one with the potential to create more energyefficient, faster-to-constru faster-t o-construct ct and highly durable structures. Thanks to engineered timber’s combination of lightness, strength and flexibility, it offers the opportunity to create longer spans with lower imposed loads on foundations or sub-structures. In fact, many leading architects and structural engineers are now of the opinion that engineered timber solutions offer the ideal option for creating the rapid-build, high-rise properties
which our ever-expa ever-expanding nding urban populations require to accommodate businesses as well as families. Recent years have already seen real progress in the development of better and more effi cient systems from leading manufacturers like Metsä Wood, with substantial investment investment in research helping bring new ones to the market. It is reasonable to conclude that with the design guidance and support available to project teams across all the construction sectors, the only limitations on the use of timber are the client’s own imagination.
Reference �1
Metsä Wood (2016) Plan B [Online] Available at: www.metsawood.com/ global/Campaigns/planb/Pages/default.aspx (Accessed: April 2016) global/Campaigns/planb/Pages/default.aspx
A L L T H E S U P P O R T Y O U N E E D
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Secant Bored Piled Walls
Driven Steel Tube
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Project focus Peer-reviewed papers focusing on the structural engineering challenges faced during the design and build stages of a construction project.
22 The Vegas Vegas High Roller observation observation wheel The Vegas High Roller is the latest and most progressive of the modern giant observation wheel concepts first developed by Marks Barfield Architects with Arup for the London Eye in the late 1990s. Unlike other cable-tensioned wheels, the structural design of the rim has been reduced to a single tubular chord carrying 28 actively stabilised, large spherical cabins (each accommodating up to 40 passengers). The benefit of improved structural structural stability is exploited by using a 35m long hub-an d-spindle assembly connecting the cable spokes to the rim. The result is an elegant and distinctive structural solution. It is also the first gi ant observation wheel to operate in a desert environment. This article describes the project’s development development and some of the challenges that this unique structure created. created. The project won the Institut Institution’s ion’s 2015 Structural Award for Arts and Entertainm Entertainment ent Structures .
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Project focus Vegas High Roller
The Vegas High Roller observation wheel John Lyle, Director, Arup UK Jason Krolicki, Associate Principal, Arup North America Rob Smith, Associate Principal, Arup North America Synopsis
The Vegas High Roller is the latest and most progressive of the modern giant observation wheel concepts first developed by Marks Barfield Architects with Arup for for the London Eye in the late late 1990s. 1990s. Unlike Unlike other other cable-te cable-tensioned nsioned wheel wheels, s, the structural design of the rim has been reduced to a single tubular chord carrying 28 actively stabilised, large spherical cabins (each accommodating up to 40 passengers). The benefit of improved structural stability is exploited by using a 35m long hub-and-spindle assembly connecting the cable spokes to the rim. The result is an elegant and distinctive structural solution. It is also the first giant observation wheel to operate in a desert environment. This article describes the project’s development and some of the challenges that this unique structure created. The project won the Institution’s 2015 Structural Award for Arts and Entertainment Structures. Vision Vis ion,, creat creativi ivity ty and and inn innov ovati ation on The High Roller (Figure 1), 1), at 168m high, is the largest observation wheel ever built. The wheel forms part of the $550M LINQ development, a 141ha site and new pedestrian-only street
in the heart of Las Vegas. Caesars Entertainment, the client and owner of the development, wanted the observation wheel to not only be the largest in the world, but to offer their guests the best experience:
“Vegas demands audacity and over-the-top. The High Roller is so much more elegant and beautiful than any other wheel. The creative intent was to have it appear to be lightweight, without a lot of structure…”
Greg Miller, Senior Vice President of Development, Caesars Entertainment The Hettema Group was appointed as the theme designer and architect for the wheel. Early collaboration between the client, architect and Arup led to the development of a reference design for a wheel structure, cabins, drive systems and boarding platforms – the key parts of an observation wheel – all heavily influenced by the engineering requirements. The scheme developed successfully minimises the visual impact of the structure, affording passengers a “floating sensation” and sense of space in large spherical cabins (Figure 2).. This is achieved using a simple, tubular 2) rim element which carries the 28 “V-frame”
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2 Figure View of cabins “floating” over Las Vegas
1 Figure High Roller viewed from the LINQ
2015 Winner: Arts and Entertainment Structures
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Project focus Vegas High Roller
P U R A
3 Figure Wheel evolution: comparison of cabin, rim, hub and spoke cable arrangements for London Eye, Singapore Flyer and Vegas High Roller
support structures that hold each cabin in single slewing bearings. Previous large observation wheels, such as the London Eye and Singapore Flyer, have wider tru ss rims and cabin support structures with dual bearings, restricting views from the cabin and making passengers more conscious of the visible structure (Figure 3). 3). The High Roller also exploits the structural benefits of a significantly longer hub/ hub/spindle spindle assembly and mobilises more lateral stiffness through the tensioned spoke cables. This 35m long hub/spindle hub/ spindle also eliminates the need for the additional diagonal spoke cables seen on the London and Singapore wheels. The overall effect is a visually simple rim and a more efficient wheel w heel stru cture. The unique nature of the High Roller wheel demanded innovation in almost every aspect of design, e.g.:
"The rotation of the wheel generates cyclic stress reversals in many parts of the structure, introducing the risk of fatigue degradation"
the construction process integrated with the rest of the LINQ development and did not disrupt an existing monorail train service passing through the site •
the main support legs lean inwards, responding to the restricted site and minimising the land required (Figure 4) a brace leg, providing the lateral stability for the main support legs, straddles a road and flood protection culvert that restricted the available locations for the piled foundations and plinths (Fig. 4) the wheel has 28 fully air-conditioned, 6.3m diameter spherical cabins (each having a capacity of 40 passengers and weighing 25t) with many additional safety systems and large double-glazed windows with excellent optical qualities (Figure 5) the wheel structure provides passenger comfort in all but the highest winds to minimise operational downtime the wheel has a 50-year design life in a desert region with moderate-to-high seismicity •
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Modelling and analysis Large observation wheels of this size have some unusual design requirements. Their slenderness makes them susceptible to wind-induced movements and buckling. To ensure passengers would have a stable ride, Arup carried out a wind time-history analysis, modelling the spatial correlation between gusts of different sizes and the lateral stiffness provided by the pre-load in the spoke cables. The rotation of the wheel generates cyclic stress reversals in many parts of the structure, introducing the risk of fatigue degradation. Structural steel components and connection details were assessed to ensure
4 Figure High Roller’s inward-leaning main support structure and brace leg
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5 �Figure Spherical cabins nearing completion at assembly
6 �Figure Cyclic stress reversals required detailed finite-
facility set up near site
element models of more complex welded parts
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the calculated fatigue life met the 50-year design life. In most instances, checks were done according to code; however, where the fabrication geometry was particularly complicated and the stress flow harder to determine, detailed finite-element analysis A A O N was used to determine the stress ranges , F S 6), and a more rigorous “hot-spot” N (Figure 6), , A I B analysis undertaken. M U L As there are no codified acceptance O C � O E criteria for wind-induced accelerations D L : A for observation wheels, the predicted T A D / movements of the wheel were simulated on T A S a custom motion platform so that the client D N A L could experience the movement. Through this : E G A intuitive and tangible experience, the client M I / H was able to choose a level of acceleration T R A corresponding to how frequently they were E E L G willing to shut the wheel due to high winds. O O G This was then used to determine the level of
added damping required to provide a smooth ride. The locked-coil spoke cables also see significant stress reversals during the wheel rotations. The published fatigue data for locked-coil cables relate primarily to axial stresses. However, as the wheel rotates the cables are also subjected to bi-axial bending and therefore the published data are not directly applicable. An analytical approach was developed to assess the cables and the results were validated with accelerated fatigue tests on cable specimens that mimicked the expected bending. The work determined that to meet the 50-year design life for the spokes, spherical plain bearings were required at the cable ends (Figure 7) to 7) to minimise the bending at the terminations. Extensive use of prefabricated structural elements simplified the construction process:
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Vegas High Roller
P U R A
7 �Figure Hub/spindle and cable ends
8 Figure Plinth at base of brace leg during construction
9 �Figure Forged hub and
spindle ends provide necessary stiffness for supporting spherical roller bearing mounting
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the tubular legs supporting the wheel hub and spindle are prefabricated in three sections. These incorporated the tuned mass dampers (to limit wind-induced vibrations) and were then connected on site using internal flange bolts. Anchor bolts connect the legs to the piled foundations via base plinths (Figure 8) which 8) which provide ductility beyond the maximum considered event seismic loads. The (rotating) hub and (fixed) spindle assemblies have forged steel ends welded to structural steel mid-sections (Figure 9). 9). The spindle and hub ends were assembled with the large spherical roller bearings on the ground and then lifted into place. The bearings themselves are designed to run for 50 years (bearing
replacement is feasible if necessary). The wheel rim structure (Figure 10) comprises 10) comprises 28 prefabricated 2m diameter tubular segments with internal flanges that are bolted together on site during the launching process. Most of the steelwork is exposed and this influenced the design of the connections and other structural details, many of which can be seen close up from the cabins. At night, thousands of programmable LEDs wash the steelwork (painted white) with varying colours, creating dynamic patterns for celebrating special occasions. The closeup lighting of structural details became as important as the long-range lighting effects. The large and complex structure presented the delivery team with significant coordination
challenges. The structure and many bespoke components were delivered through an international collaboration of engineers and contractors based in nine countries. Arup worked closely with American Bridge, the general contractor for the wheel structure, during the development of construction documents to ensure the design progressed down an economically and logistically viable route. The cabins were procured via a design-and-build contract let to LeitnerPoma of America via a reference design and performance specification developed by Arup in London. The wheel drive systems, themselves significant structures, were procured using a similar process, with most of the fabrication and factory-based testing
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10 �Figure Photo call for construction team as rim nears completion
eventually included cabins, drive equipment, electrical equipment, lighting, and all their associated nuts, bolts and brackets. The 3D model served two key purposes: having all the components in one spatial model helped with clash detection having a visual aid for coordination discussions allowed all parties to understand how their components related to the whole •
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Value, susta Value, sustainabi inability lity and and societal societal benefit The project is a great example of how early collaboration between the client, engineer and contractors was critical in overcoming the technical and schedule challenges associated with this unique structure (Figure 12).. The innovative design has provided the 12) client with a valuable long-term asset and is currently the world’s tallest observation wheel. The structure is a significant evolution of those used by predecessors and has resulted in comparative material savings and reduced fabrication and installation time. A large portion of the temporary works structures used during the construction are being re-used in the temporary works for the new Tappan Zee Bridge, currently under construction, in New York State. The High Roller is a catalyst for the urban regeneration of a previously poorly used part of Las Vegas. It forms a major feature on the new pedestrian-only street, drawing people away from the busy Las Vegas Boulevard “Strip”. More importantly, it now provides a city, often only noted for pastiche, with an elegantly engineered leisure and entertainment facility that appeals to a wide range of the potential user demographic.
�Figure 11 P U R A
carried out in the Netherlands. Many of the final structural components for the High Roller were physically too large and heavy to transport economically to site, and a key challenge was to discretise the permanent works into sections that could be shipped and lifted into position. Through a detailed analysis of the reference design, American Bridge identified optimal locations for bolted splices to enable shipping, trucking and lifting operations and then fed these back into the detailed design process of the permanent works undertaken by Arup. This collaborative approach gave a schedule advantage, allowing the temporary and permanent works to be designed in parallel, and led to a more efficient structural structu ral
design tailored to the contractor’s preferred fabrication and erection methods. A lot of the required tolerances exceeded those typically associated with steel structures and the unusual interfaces required careful management; most notably the interfaces between the static elements (boarding platform and drive equipment) and the moving elements (rim and cabins). To coordinate these interfaces, a detailed three-dimensional (3D) Building Information Modelling (BIM) model (Figure 11) was 11) was developed in Navisworks1. This started with the 3D structural steel model and developed with the subcontractors’ components. The model
BIM model used for coordination
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Project focus Vegas High Roller
12 Figure Completed structure
Project credits Client: Caesars Entertainment Client: Caesars Theme designer and architect: architect: The The Hettema Group Reference design and structural engineer: Arup Contractors: Wheel structure: American structure: American Bridge Company Drive system: Schwager system: Schwager Davis Inc. Cabins: Leitner-Poma of America Inc. Boarding platform architect: Klai architect: Klai Juba Wald Architects Boarding platform contractor: contractor: WA WA Richardson Builders Location: Las Location: Las Vegas, Nevada, USA
Reference �1
Autodesk (2016) Navisworks [Online] Available at: www.autodesk.co. www.autodesk.co.uk/products/ uk/products/navisworks/ navisworks/ overview (Accessed: April 2016)
Further reading Almufti I., Christie N., Crowther A. et al. (2014) ‘The Vegas High Roller’, The Arup Journal , Issue 2, pp. 4–29 Smith R. and Crowther A. (2014) ‘The Las Vegas High Roller: the world’s largest observation wheel’, Proc. 37th IABSE Symposium: Engineering for Progress, Nature and People , Madrid, Spain, 3–5 September, pp. 2357–2364 Schwarz D. and Callaghan J. (2014) ‘Construction of the Las Vegas High Roller Observation Wheel’, Proc. 37th IABSE Symposium: Engineering for Progress, Nature and People, Madrid, Spain, 3–5 September, pp. 2349–2356 Lyle J. and Christie N. (2014) ‘The structural mechanization of giant observation wheels’, Proc. 37th IABSE Symposium: Engineering for Progress, Nature and People , Madrid, Spain, 3–5 September, pp. 2341–2348 P U R A
20th October 2016 Royal Berkshire Conference Centre Madejski Stadium, Reading, Berkshire, RG2 0FL
1 Day Technical Seminar
Evolving
Concrete
®
Join us for a full programme of talks covering:
PERFORMANCE, SPECIFICATION AND PRACTICE
KEYNOTE SPEAKERS
Stephen Hodder Immediate Past President RIBA Alan Crossman Current President of IStructE For up-to-date details and to book your your place visit:
www.evolving-concrete.org
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Professional guidance Articles that provide information and advice on everyday matters affecting the practising structural engineer enginee r.
30 Engineer’s 30 Engineer’s Guide to PI Claims. Part 5: Defence arguments – partial defences 32 Managing Health Healt h & Safety Safety Risks No. 51: Hazards from gas 34 Confidential 34 Confidential Reporting on Structural Safety (CROSS)
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Professional guidance
June 2016
PI claims
Engineer’s Guide to PI Claims Part 5: Defence arguments – partial defences Our series from Gr Griffi iffi th ths s& Armour turns Armour turns its attention from complete to partial defence arguments when faced with a PI claim. In May, we started to look at how engineers and their insurers might defend professional negligence claims, focusing particularly on arguments which, when successfully deployed, operate to defeat claims in their entirety 1. Where such complete defences are not available, or where there is a risk that they might fail for some reason, engineers should also consider what “partial” defences they might have at their disposal. Rather than defeating the claimant’s case altogether, these defences serve instead to reduce any award of damages that a court might otherwise have made. Any such reduction should, in principle, reflect an equitable apportionment of responsibility. It is therefore not necessarily precise or scientific in its application, and that makes for uncertainty in practice over what the financial benefit of running one of these defences might be. However, the same partial defence arguments can also be used to apply pressure on claimants in preaction negotiations, either to abandon their claims altogether or to accept a low-value commercial settlement.
Contributory negligence The law recognises that a client is entitled to place reliance on the professional service provided by an engineer, and this basic premise is what underpins any action in negligence. However, just as common sense dictates in the wider world that placing reliance on someone or something (e.g. protective clothing) should not entitle an individual to abrogate all responsibility for any subsequent
damage or injury that might occur, there are limits to how far an engineer’s client can plead as a matter of fact that they were solely reliant on the engineer’s performance in all respects (Case study 1). 1).
Joint liability The term “contributory negligence” is often misused because, strictly speaking, it refers only to cases where there has been negligence on the part of the claimant. More usually, it is possible to argue that one of the other members of the construction team had failed in their responsibility, in which case the engineer might seek to join that party into the action as a second defendant. This opportunity arises in cases of joint and several liability, i.e. where two or more parties are liable to the same claimant for the same loss (Case study 2). 2).
Failure to mitigate loss Both in contract and in negligence, an injured party has a duty to take reasonable steps to
mitigate any losses suffered as a result of a defendant engineer’s breach of duty. Where a claimant fails to discharge that duty, the court will make an appropriate deduction from any pleaded losses so as to reflect what it considers should properly be recoverable. The principle has obvious application in the context of construction disputes, particularly in relation to delay claims, supplier failure or wherever consequential losses are involved (Case study 3). 3). Finally, it should be noted that engineers can seek to exclude in contract any liability for consequential losses, especially in collateral warranties to purchasers and tenants. This can be achieved in negotiation by reminding the client that businesses such as the food plant owners in Case study 3 will invariably carry a commercial insurance package containing a business interruption section. That policy should cover the majority of such losses, and there should therefore be no need to transfer this risk to an engineer in contract.
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Case study 1
Case study 2
A simple example of contributory negligence is a fairly typical claim scenario in which a structural engineer prepares a survey report on a house prior to purchase and is later accused of having negligently failed to advise of some defect (such as a deflection in the roof truss) which had been noticed by the purchasers themselves during their own visit to the building a few days previously. The purchasers would argue that, had they been so advised, they would have negotiated a lower purchase price and that the engineer should therefore compensate them for the di fference. The purchasers are not engineers, and they are entitled to rely on the skill and experience of their professional advisers. But this does not mean that if they themselves were aware of a problem independently of their engineer’s report (because there was clear evidence, visible to the naked eye from ground level, that the ridge was sagging in the middle), then they will be entitled to plead total reliance on the engineer’s report, which simply omitted to comment on it. A judge would be highly critical of an engineer for having failed to advise on something that even a layperson could have said was wrong. In practice, we would struggle to argue with that finding, but would focus instead on arguing that the purchasers purcha sers had suffi cient awareness awaren ess of the defect to have taken better care for themselves. If the sagging in the roof structure was so obvious, why did they not query the engineer’s failure to advise upon it at the time? Perhaps they had not read the report repor t with suffi cient care; care ; in which case, how can they purport to have relied upon it as they say they had? As is always the case, any such defence depends for its success on evidence, evidenc e, and it mi ght be diffi cult to prove at trial what an individual’s state of knowledge was several years previously previously.. Typically,, a court would be more Typically sympathetic to a house purchaser in this situation than to a more experienced commercial property owner, where a larger percentage reduction might be awarded. Contributory negligence is therefore always more useful as a defence against an educated or experienced claimant than against a lay person.
Under a traditional procurement, one of our engineer clients had a duty to visit site at various stages of construction and monitor the contractor’s performance for quality. The engineers failed to identify that the contractor had deviated from their drawings when laying the foundations. The employer had a strong case in this instance against both the engineers and the contractor, contractor, but decided to sue only the engineers. The engineers were the easier target on this occasion owing to an indemnity provision in their appointment and also the amount of professional indemnity insurance that they had agreed to maintain, but in other cases the claimant’s reasons for issuing proceedings against one culpable party and not the other are less than clear. Fortunately,, the law in most jurisdictions Fortunately allows us, as defendants in such cases, to argue that we are jointly and severally liable (if at all) with one or more other parties; that those other parties are therefore liable to pay us a contribution to any damages award against us; and that the court should therefore therefor e hear our claim for contribution as part of the principal dispute rather than after the event. That was our argument in this instance and the appropriate procedural steps were taken to join the contractor into the formal legal proceedings, the effect being essentially the same as if the claimants themselves had brought their action against both defendants. Having reached common ground about the true value of the claimant’s losses, we negotiated settlement with a 60% contribution from the contractor contractor.. We also made considerable defence cost savings through having reached settlement with both parties at the same time, rather than settling the principal action first and our contribution proceedings only after the event.
Case study 3 Our clients had designed a new building which was to be used as a food processing plant. A fire broke out four years after handover,, and it was established that handover considerably more damage had been done in the incident than would have
been suffered had the steel frame been designed in accordance with the employer’s requirements, specifically in relation to fire resistance. The principal loss was the cost of reinstating the damaged parts of the building and its contents. But there were also consequential losses in this case which consisted of the plant owner’s loss of trading profits during the period between the fire and completion of the reinstatement works. Loss of profit is often a largely speculative head of loss in any event, and so as a matter of course we engaged expert forensic accountants to examine from the claimant company’s accounts how, based on previous trading, they had arrived at the sums in their schedule of loss. But in this case our investigations also revealed that, throughout the period in question, the owners had been supplying some of the same client retailers from their other factories as they would otherwise have served from the damaged plant. We also managed to establish that the other plants apparently had capacity to increase their output. While, ultimately, the engineers’ design failures had been factually causative of a hiatus in production at the damaged plant, we argued that the claimants had missed an obvious opportunity to mitigate their loss by simply re-routing their supply operations temporarily temporarily to one of their other plants, where most, if not all, of the affected orders could have been serviced. They were unable to explain why they had failed in this opportunity, and since that amounted to a breach of duty on their part, we were able to negotiate a further reduction in the value of the subsequent settlement deal. REFERENCE: 1) Griffiths & Armour (2016) ‘Engineer’s ‘ Engineer’s Guide to PI Claims. Part 4: Defence arguments – complete defences’, The Structural Engineer , 94 (5), pp. 34–35
Griffi ths & Armou r is a leadi ng independent and privately owned UK insurance broker and risk management adviser. For further information, scan the QR code or visit www.g riffi thsan darmo ur.com . Griffi ths & Ar mour i s authorised and regulated by the Financial Conduct Authori ty.
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TheStructuralEngineer
Professional gu guidance
June 2016
Health and safety
Managing Health & Safe Safety ty Risk Risks s No. 51: Hazards from gas There have been several recent cases of houses being destroyed following gas leaks. The fact that such incidents fail to raise much alarm shows how common they are. Yet Yet there should be no complacency, since one of the most infamous failures of recent history, Ronan Point, was initiated by a domestic leak and subsequent igniti on that blew out one supporting panel i n the system-built block of flats. Gas leaks and their consequences should therefore be one of the standard hazards considered in any risk assessment. At least six types of gas need to be considered: • domestic (natural) gas • methane • sewer gas • carbon monoxide (CO) • carbon dioxide (CO2) • radon The consequences to be considered are explosion and poisoning.
Natural gas The most common risk from natural gas is the possibility of an explosion within a domestic property; the leak may well come from poorly fitting appliances. To mitigate against this, the law in the UK requires that appliances be fitted only by registered “Gas Safe” operatives. The possibility of gas leakage from older mains and degrading underground services also exists and all the utilities have long-term projects aimed at bring such services up to modern standards. Short-term risks may become exacerbated when services are endangered, as they have been, by gross disturbance in flooding incidents (the 2015 Tadcaster bridge collapse in the UK was accompanied by fear of fracturing the gas mains which crossed it). Historically, gas leaks have caused some serious accidents. Outside the UK, there has been more than one incident caused by illegal tapping into oil pipelines creating a vapour explosion. In Russia, in 1989, a
leaking natural gas pipeline created a highly flammable cloud which was ignited by sparks from two passing trains. Both trains were totally destroyed in the resulting blast, with around 575 deaths (many of them children) and around 800 people injured. One of the worst-ever UK c atastrophes, the destruction of the Piper Alpha North Sea oil platform in 1988, was initiated by a gas leak. The scale of the disaster was enormous: 167 people died and the commercial consequences were substantial. In 2004, the Stockline plastics factory in Glasgow was destroyed in a huge explosion. Nine people died and 40 were injured. The cause was a gas leak f rom a corroded pipe buried under the factory. The lesson here was that a leak was always a theoretical possibility, yet because the pipe was buried, its condition could not be determined. In 2014, a whole string of explosions occurred in Kaohsiung, Taiwan, Taiwan, when leaking gas seeped into roadside storm drains and ignited. Several kilometres of road surface were destroyed and there were many deaths.
Methane Methane is natural gas generated by decaying hydrocarbons located below ground. Historically, it has been behind many mine explosions. Methane is a potential hazard in any underground works (and that includes all tunnels and sewers). The dangers it can pose are highlighted by the 1984 tragedy at Abbeystead pumping station in Lancashire. The valve house for this system was underground. On the day of the incident, 44 people were present to see a water pumping demonstration. Just after pumping started, there was a flash and explosion causing severe damage: 16 people were killed and all others present were injured. The explosion was caused by ignition of accumulated methane and air; the methane might have been dissolved in water which leaked into the system. During design, the hazard of gas accumulation had not been considered. Significant amounts of methane are produced on landfill sites and strategies are required for controlling it. This applies especially when houses are built on top. Extra care is warranted when large amounts of gas are stored. In 2015/16
in California, a large leak started from an underground storage facility. Approx. 100 000t of methane escaped before the leak was plugged. Eleven thousand nearby residents had to be evacuated and a state of emergency was declared.
Sewer gas Sewer gases may include a mixture of toxic and non-toxic gases created by decomposition of household and industrial organic waste. The gas can be a nuisance (due to its smell) but may also pose health hazards. Such gases ought to be excluded from buildings if the plumbing incorporates appropriate traps.
Carbon monoxide The dangers from CO are mostly poisoning (every year in the UK about 200 people are admitted to hospital with CO poisoning and several die). The gas is created when the air supply is inadequate, leading to incomplete combustion, or where fume extraction is inadequate (e.g. blocked flues and chimneys). chimneys). Potential gas sources include domestic fires and boilers. A recent, wellpublicised case was that of two children killed while sleeping in a holiday let in Corfu. The cause was CO emanating from a badly maintained gas boiler. The lessons are that regular and proper maintenance is necessary and that free air supply and free fume extraction must be ensured. Additionally, all houses are urged to have CO monitors as a mitigation measure.
Carbon dioxide This gas is not harmful in small quantities, but at higher concentrations can be very dangerous, causing loss of consciousness. CO2 is heavier than air so may accumulate in low, confined places. It may be encountered in high concentrations in a workplace. CO 2 is classified as a substance dangerous to health under the COSHH regulations 1.
Radon Radon is a colourless, odourless gas, formed by the radioactive decay of naturally occurring uranium. The risk varies across the UK according to the local geology, but it does feature in the Building Regu lations, which require a risk assessment and potential implementation of preventive
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33
measures, mainly sealing under the floor plus ventilation to eliminate build-up. General awareness
Designers need to be aware of the general hazards related to gas. In some cases, the best design solution to eliminate the risk of explosion is not to permit a gas supply within the structure, but this is not always possible. Clearly, measures to minimise the risk are mandatory and these include proper installation, provisions to isolate supply and measures to minimise the risk of in-service degradation. Designers need to be aware of the inherent dangers of methane for underground structures or for those built on filled sites; the same applies to radon. Thereafter,, another universal safety p rinciple is to ensure that Thereafter where gas is supplied (or might be present), all leaks are detectable with warning. In domestic premises, this can be achieved in part by use of monitors (natural gas is supplied wit h an additive to give it an odour as an aid to detection). Further management measures are to ensure that there are cut-off facilities and to have emergency plans of what to do if leaks are detected. The dangers of leaks are exemplified by the 1984 Bhopal disaster in India – generally considered to be the world’s worst industrial accident. The Bhopal plant was used to p roduce pesticides and involved use of a toxic gas (methyl isocyanate) and other chemicals. One night, there was a leak and gas permeated over a large area among poor dwelling dw ellings s nearby. The official death deat h toll was over 2250, but other estimates reach many multiples of that figure. Large numbers of people suffered severe illness, including blindness. The clear lesson is that for any such plant (or any plant or civil structure containing gas), the possibility of a leak and all its consequences need to be considered. There needs to be a detection policy and an emergency evacuation policy. This guidance note has been prepared by the Institution of Structural Engineers’’ Health and Safety Panel. Engineers
REFERENCE:
1) Health and Safety Executive Executive (2016) Control of Substances Hazardous to Health (COSHH) (COSHH) [Online] [Online] Available at: www.hse.gov. uk/coshh/index.htm (Accessed: May 2016)
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FURTHER READING:
The Institution of Structural Engineers’ Health and Safety Panel (2012) ‘Managing Health & Safety Risks (No. 9): Hazardous materials’, The Structural Engineer , 90 (10), p. 23 The Institution of Structural Engineers’ Health and Safety Panel (2014) ‘Managing Health & Safety Risks (No. 27): Confined spaces’, The Structural Engineer , 92 (5), p. 28 Public Health England (2016) UKradon UKradon [Online] [Online] Available at: www.ukradon. org/ (Accessed: May 2016) General information on public health in the UK (methane, radon, etc.) is available at: www.gov.uk General information on gas safety is available at: www.hse.gov.uk/
Note: Indicative spans for given loads please contact our office for beam types for other spans & loading situations.
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TheStructuralEngineer
Professional Profession al guidance
June 2016
CROSS
Confidential Reporting on Confidential Structural Safety (CROSS) The latest CROSS newsletter from Structural-Safety includes news of an initiative to investigate weatherrelated damage to buildings. CROSS has launched an additional category of reports to capture damage to buildings and related infrastructure from the effects of weather. There appears to be a greater number of storms and extreme weather events and the question is whether our buildings are being affected more severely now than was the case previously. Accordingly, in the UK, the Department for Communities and Local Government has sponsored a programme to gather evidence which could help determine what changes might be required to future building regulations. Reports are being requested from all local authorities in England, and also in Scotland, Wales and Northern Ireland. Reports will be welcome too from anyone else who observes damage from weather effects. The aim is to build up a record of evidence, and events of interest include: • extreme rainfall • high winds • flooding (including tidal and surge effects) • freezing temperatures • ground movement • high temperatures • moisture • snow/sleet/hail/ice Reports will be submitted through the website and the usual confidentiality will apply to reporters, but locations will be recorded so that these can be linked to maps and to the severity of weather at the time. Categories of damage will be allocated so that the data can be analysed. The programme has started and reports are welcome. As with all CROSS material, there will be lessons that can be learned by designers, contractors, regulators, building control officers and academics. aca demics. Results R esults
will help to improve our knowledge and participation will help others. The success of the CROSS programme depends on receiving reports, and individuals and firms are encouraged to participate by sending concerns in confidence to www. structural-safety.org/confidential-reporting/ submit-report/.. submit-report/ Reports in the current newsletter1 are summarised below. Readers can register to receive the newsletter at www.structuralsafety.org.. safety.org
on domestic roofs. Unfortunately, because the market was buoyant, many “engineers” entered the market and drove the prices for assessments down by undertaking far less rigorous analysis, and suggesting that far fewer fixings were adequate.
Lifting large double-glazing unit Inadequate instructions were provided by a double-glazing pane supplier on how to lift and move their product, supplied on a flatbed truck, off the truck and onto the works.
Bridge wing wall collapse The masonry wing wall of a bridge fell as a single section and came to rest against an adjacent pile. Although the roles and responsibilities placed on individuals on site were clear, there there was a lack of direction on who held ultimate responsibility for identifying the need for temporary works.
Stored glazing panels
Incentivising safe behaviour through standard agendas
Falling lath-and-plaster ceiling
A reporter was investigating a near miss involving concrete construction in which precast and in situ concrete were used in combination. This type of construction offers efficiencies and, a nd, as in this instance, inst ance, can reduce reduc e the number of man-hours worked at height. It does, however, bring its own risks, and these need to be understood. The design had developed from all in situ to hybrid precast/ in situ over a series of design meetings. It was the combination of precast and in situ construction that led to the near disaster in which fatalities were a real possibility.
Sudden hole in piling mat This concerns a near miss on a site where a piling wall was being constructed. The reporter says that, while digging a trench, a 450mm diameter hole appeared in the pile mat about 0.5m from the guide wall. As the grab was being lowered into the trench, bentonite from the wall panel gushed out from the hole.
A reporter has been undertaking facade inspections for insurers across many buildings in the UK and the same issue keeps appearing on every site: glazing is not individually tied back to storage frames or to a secure place when being stored.
A 100-year-old lath-and-plaster ceiling in a shop unit collapsed in part, injuring the shopkeeper.. There were signs of d istress shopkeeper (cracking) shortly before collapse. Upon inspection, says the reporter, it appeared that the 35–40mm thick plaster had become de-bonded from the laths. At the time, some “soft” demolition was being carried out on the floors above.
Importance of bearings Bearings are an important component of the superstructure. A reporter says that they are often underestimated in their long-term characteristics and behaviour. It is vitally important to have regular inspections of bearings and seatings, with maintenance as required and the facility to replace faulty components. The reporter wonders whether any systematic study on the overall issues of bearing assembly and associated requirements has been done.
Comments PV panel installation A reporter’s firm used to carry out design work for installers of photovoltaic panels, many
Further details and comments on these reports from the CROSS panel can be found online at www.structural-safety.org www.structural-safety.org..
REFERENCE:
1) Structural-Safety.org (2016) CROSS Newsletter No. 42 – April 2016 [Online] Available at: www. structural-safety.org/publications/view-newsletter/?newsletter=8408 structural-safety.org/publications/view-newsletter /?newsletter=8408 (Accessed: May 2016)
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TheStructuralEngineer June 2016
35
Technical Articles that are technical in nature; focusing on methods of analysis, material properties and aspects of design of structures.
36 An err error or in Timoshenko Timoshenko’s ’s “Theory “Theor y of Plates Plates and Shells” 40 Conserva Conservatio tion n compendium. Part 18: Noninvasive qu quantita antitative tive app appraisal raisal of historic floor structures
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TheStructuralEngineer
Technical
June 2016
Theory of Plates and Shells
An error in Timoshenko’s An “Theory of Plates and Shells” Angus Ramsay Rams ay MEng, PhD, CEng, FIMechE, Owner, Ramsay Maunder Associates; Independent Technical Editor, NAFEMS Benchmark Challenge Edward Maunder MA, DIC, PhD, CEng, FIStructE, Consultant, Ramsay Maunder Associates; Honorary Fellow, University of Exeter, UK
Introduction The authors recently conducted a study into the elastic behaviour of thin (Kirchho (Kirchhoff) ff) plates using commercial finite-element (FE) software. In attempting to verify the FE solution, it was compared to results presented in Timoshenko’s Theory of Plates and Shells1 and a significant difference was observed. This article presents the work conducted to uncover the reason for this difference and reveals an error (probably typographical) in the text. The source of the error is identified and it is demonstrated how such errors might propagate into other texts on the subject of plates. The significance of the error to the practising engineer is also discussed.
Plate configuration considered The plate considered is rectangular with an aspect ratio b/a b/a.. It is simply supported on two opposite sides and loaded with a uniformly distributed load (UDL), as shown in Figure 1. 1.
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Figure 1 Plate configuration
This problem is considered in Article 48 (p. 214) of Timoshenko’s text 1 and the deflections and moments at points A and B are reported in the text (Table 47, p. 219) for a Poisson’s ratio of ν = 0.3. This table has been reproduced in Table 1 where 1 where D is the flexural rigidity of the plate and w is is the transverse displacement. In Figure 2, 2, an infinitesimal region around the centre of the plate is shown, together with the moments and stresses. The UDL causes sagging moments in both longitudinal and transverse directions, which induce stresses in the plate, linearly distributed across the thickness, as shown, with the stresses on the top surface both being compressive. compressiv e. Note that the moment m x causes a direct stress in the x direction direction σ x .
FE analysis of plate The aspect ratio of the plate considered was 0.5 and the authors chose to study the convergence of the moment ratio (defined
in Fig. 2) 2) with both mesh refinement and span-to-thickness span-to-thickn ess ratio a/t . The reason for considering convergence with spanto-thickness ratio was that the FE system used only provided thick (Reissner–Min (Reissner–Mindlin) dlin) plates, and it was therefore necessary to ensure that the chosen thickness was small enough to have removed the influence of shear deformation, which is not considered in the thin (Kirchhoff) formulation being investigated. The results from this converge convergence nce study are summarised in Figure 3, 3, where an initial mesh of 1 × 2 = 2 elements was used with uniform mesh refinement and span-tothickness ratios between 2 and 2000 were studied. Both studies converge to a moment ratio of 10.19 as shown in Fig. 3. 3. The ratio of the moments presented in Timoshenko 1 is 12.11, so there is a significant difference,, approaching 20%, between the difference FE values and the published moments, and this needs further investigation investigation..
2 �Figure Moments and stresses at centre of plate (point A) and definition of moment ratio
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Table 1: Timoshenko’s results Point A
Point B
0.5
0.01377
0.1235
0.0102
0.01443
0.1259
1.0
0.01309
0.1225
0.0271
0.01509
0.1318
2.0
0.01289
0.1235
0.0364
0.01521
0.1329
∞
0.01302
0.1250
0.0375
0.01522
0.1330
3 �Figure Convergence of moment ratio at point A (FE)
Development of computer program Timoshenko’s text provides an expression Timoshenko’s for the plate transverse displacement w as as a single, infinite series (attributed to Levy and presented on p. 217, Eq.(h)), which may be twice differentiated to produce the curvatures and then, through the constitutive relations, the moments – see p. 39 for an example1. The expressions for the moments were coded into a small program so that they could be evaluated at a given point within a plate of arbitrary aspect ratio b/a. The summation implied by the series solution is carried out in a loop for which only odd indices are considered and the upper value of the index is maintained as a variable in the program. Rapid convergence is observed, with the moment ratio for 26 terms in t he series being 10. 10.17843 17843 (Figure 4). 4). The program produces values of displacement and moment at any point. These values may be used to plot distributions across the plate, and inspection
of these distributions for satisfaction of the kinematic and static boundary conditions will provide verification that the program is correct. The displacement field, not shown in this article for conciseness, demonstrates that the zero displacement condition along the simply supported edges is satisfied and that the field possesses the expected symmetry about the lines x = a/2 and y = 0. The Cartesian components of moment are shown in Figure 5. 5. The static boundary conditions require there to be zero bending
moment along all edges and this is clearly seen. The torsional moments are not required to be zero along the boundary, as Kirchhoff theory is assumed, but they should be zero along the two lines of symmetry and this is seen to be the case. The principal moments and the von Mises moment field M νM are also shown in the figure and it is seen that the point of first yield is at point B, the centre of the free edges. An additional FE result was produced using a pure Kirchhoff finite element. This gave a moment ratio of 10.1784 1784 which, to four decimal places, is identical to that produced by the program, thus independently verifying the program. The moment ratios from the four independent sources considered are shown in Table 2. The results shown in Table 2 indicate 2 indicate that there is something amiss with the values published in Timoshenko’s text, at least for an aspect ratio of 0.5, and further investigation of the individual moment components used in the moment ratio show that it is the value of M y at point A which is in error, with the value in the text being 0.0102 and the value from the program being 0.0122. The table of point results produced in Timoshenko (and reproduced in Table 1) is attributed to a 1936 publication by Holl2 studying the problem presented in
Table 2: Summary of moment ratios at point A from different sources Source
Moment ratio at point A
Timoshenko
12.11
FE (Reissner–Mindlin)
10.19
Program
10.18
FE (Kirchhoff)
10.18
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TheStructuralEngineer
Technical
June 2016
Theory of Plates and Shells
4 �Figure Convergence of moment ratio at point A (program)
in the book value, since, if the last two digits are transposed, then it becomes 0.0120 and the error reduces to –1. –1.64%, 64%, which is much more in line with the error in the other values reported in Table 3. Practical conclusions
5 �Figure Moments from program
this article. In the era when the original publication was prepared, digital calculators/ computers were not available and so it is likely that the moment values were calculated by hand using tabulated data to obtain the hyperbolic trigonometrical functions and taking only a small (but presumably presumab ly suffi cient) number numb er of terms
in the series. The difference between the published values and those produced by the program is reasonably small for all but M y for an aspect ratio of 0.5, as shown in Table 3. As already noted, the values of M y at point A for the book and program are, respectively, 0.0102 and 0.0122. It is interesting to surmise that there is a typographical error
This article has uncovered, by chance, an error in the published result for the transverse moment at the centre of the plate configuration considered when the aspect ratio is 0.5. It illustrates the sort of care required by practising engineers when taking published data at face value, even when it comes from such revered texts as Timoshenko’s 1. With the wide availability of FE systems, the practising engineer can, and should, check the values they are going to use in the design or assessment of a structural member. It is also interesting to note the fact that published errors can propagate. In this case, erroneous data presumably first published in the first edition is still being used in t he 28th reprint of Timoshenko’s text 1 published in 1989 and also appears in Szilard’s 2004 publication on Theories and Applications of Plate Analysis 3 (case number 103). The authors of this current article have contacted the publishers of Timoshenko’s text1 regarding this error, asking whether it might be corrected at a future reprint. However,, it is understood that no further However reprints are likely. This raises the question of how one then might protect practising engineers against the propagation of erroneous published data. One way to
Table 3: Percentage difference in displacements and mome nts Point A
Point B
0.5
0.41
–0.12
–16.03
–1.47
–1.50
1.0
–0.03
–0.04
0.08
0.52
0.54
2.0
0.02
0.03
0.03
0.05
0.07
∞
–0.01
–0.05
–0.05
0.01
–0.01
Notes (i) Percentage differences calculated as 100 × (book – program)/ program)/program program (ii) The values in the table converge very rapidly with i ncreasing aspect ratio and the value used for the “infinite” aspect ratio was 10.
www.thestructuralengineer.org 39
do this would be to have an online repository of such errors which engineers can access to check that there are no reported errors in the data they are proposing to use. In the absence of such a facility, the best one can do is publish the finding, as here, with the hope that it w ill reach the intended audience. With regard to the engineering significance of this finding, the error leads to an under-prediction of the minor (transverse) component of the moment at the plate centre. The engineer designing a steel plate might use the moments to calculate the von Mises moment and ensure that this is below the yield moment for the steel being used. Since the von Mises moment is greater at the centre of the free edge (point B) than at the centre of the plate, then provided the engineer notices this, the erroneous value in the table would never be used. For a designer of a reinforced-concre reinforced-concrete te slab, however,, this moment value may well however be used to size the reinforcement lying parallel to the y axis and a n under-
prediction of some 16% might lead to a situation where the structure is pushed out of the elastic region and into the plastic region. The degree to which this will occur should, however, be well within the ulti mate capacity of the slab, but may be undesirable in terms of serviceability issues such as cracking of the concrete.
Portugal for running the plate through his Kirchhoff equilibrium FE software. Professor Husain Jubran Al-Gahtani of the King Fahd University of Petroleum and Minerals, Dhahran, in the Kingdom of Saudi Arabia for independently verifying the results produced by the program using Mathematica.
Acknowledgements Acknow ledgements
Contact details
The authors would like to thank: Professor J.P.B.M. J.P.B.M. Almeida of the Department of Civil Engineering and Architecture, IST, IST, University of Lisbon,
Angus Ramsay:
[email protected] Edward Maunder:
[email protected]
References �
1
Timoshenko S.P. S.P. and Woino Woinowsky-Krieger wsky-Krieger S. (1989) Theory of York, USA: McGraw-Hill Plates and Shells (2nd ed.), New York,
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2
Holl D.L. (1936) ‘Analysis of thin rectangular plates supported on opposite edges’, Iowa Engineering Experiment Station Bulletin, 129
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3
Szilard R. (2004) Theories and Applications of Plate Analysis, New Jersey, USA: Wiley
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TheStructuralEngineer June 2016
Technical Non-invasive appraisal
Conserv Conser vation compendium Part 18: Non-invasive quantitative appraisal of historic floor structures
This article forms part of the Conservation compendium, which aims to improve the way engineers handle historic fabric through the study of historic materials, conservation conservation philosophy, forms of constructi construction on and project examples. Articles in the series are written by Conservation Accredited Engineers. The series editor is James Miller.
Jon Avent BSc(Hons), CEng, MIStructE, IHBC, Accredited Conservation Engineer; Chair, Conservation Accreditation Register for Engineers Introduction
When existing buildings need to be inspected and assessed, the structural engineer is often presented with the challenge of needing X-ray X-r ay eyes. Lacking such a gift, and despite what clients may assume, the engineer draws instead on knowledge and experience to make value judgements in many situations, with appropriate margins of safety and consideration of appropriate risk incorporated along the way. Codes of practice and British Standards are not to be ignored, but are a useful tool to assist with this process. This article aims to discuss some of the issues, challenges, tools and techniques available to the practising structural engineer when assessing existing structures. While the article focuses principally on floor structures, the techniques can be used on a range of applications to provide an understanding of how existing structures are actually behaving, rather than how we might think they are working. BS 7913:20131 states in its introduction:
“The immediate objective of building conservation is to secure the protection of built heritage, in the long-term interest of society. Issues relating to building conservation are often complex and interwoven. The conservation of historic buildings requires judgement judg ement base based d on an unders understandi tanding ng of principles informed by experience and knowledge to be exercised when decisions are made. British Standards that are applicable to newer buildings might be inappropriate. The decision to conserve historic buildings can be justified on social, cultural, economic
1 Figure Phasing plan for Dunluce Castle
and/or environmental grounds, and usually a and/or combination of these. Conflicting pressures often need to be balanced to assist good decision making. Good conservation depends on a sound research evidence base and the use of competent advisors and contractors.” This is an important statement which focuses the mind, hopefully towards an approach that truly adopts the highest possible standards of conservation principles. It is important to recognise that British Standards are codes of practice that take the form of guidance and recommendation recommendations, s, and are generally not mandatory specifications that infer compliance or non-compliance non-compliance.. The structural engineer is able to seek alternative means of ensuring structural adequacy. adequacy. Where Whe re to to start start? ?
Gaining the greatest possible understanding of a building at the earliest opportunity is at the very top of any appraisal process,
and dating is a valuable tool available to the structural engineer. engineer. As with other forms of “dating”,, building dating can be challenging “dating” and lead up blind alleys; but ultimately it can be tremendously rewarding, yielding valuable information about building construction materials and techniques simply by knowing when a building was constructed. Figure 1 shows the phasing plan for Dunluce Castle, Northern Ireland: this simple timeline provides layers of additional information to aid interpretation and understanding. Structural movement that coincides with different phases of construction would be interpreted differently differently from movement within a phase of construction, and may allay concerns and avoid the need for intrusive investigations. In this way, dating may help simulate the impression of “X-ray eyes”. The structural engineer’s “go to” equation of wL2/8 for bending moment and 5wL4/384EI for deflection of a simply supported, uniformly loaded beam provides a perfectly reasonable starting point when making
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2 Figure Simply supported beam
initial assessments (Figure 2); 2); however, in the majority of cases this is a simplistic and conservative approach due to the idealised nature of support conditions. When using the data to establish predicted stress levels and deflection characteristics, the engineer might use properties for Young’s modulus that they are comfortable with, but this may be a further conservative factor in the appraisal. With modern codes containing in-built factors of safety for stress and deflection, the level of conservative assessment rises further. In practice, structures are rarely simply supported and a degree of end fixity exists (Figure 3). 3). In the case of full end fixity, the maximum deflection is on one-fifth of the simply supported prediction, which further illustrates the potential “worst case” assumptions in the simply supported approach to appraisal. When the use of such simplistic analysis techniques fails to yield a favourable conclusion for a listed building or important heritage asset, it is reasonable to look at alternatives to establish more accurate results. In some circumstances, this conservative approach is instead taken as definitive and unnecessary strengthening is proposed. There is also a risk that the structure may be condemned unnecessarily. In the case of historic buildings, this can result in irreparable damage or loss of fabric. In conservation terms this is in complete conflict with the core principal of seeking to adopt minimum intervention when dealing with repairs or renovation.. In commercial terms it can also renovation result in clients expending limited financial resources carrying out works that are unnecessary,, or losing structure that is unnecessary perfectly serviceable.
3 Figure Influence of end support fixity
4 Figure Hidden floor defects
cladding elements, such as ceilings, floor boards and strutting, can all act to enhance the stiffness of floors, but their influence is generally diffi cult to quantify quanti fy analytically. analyti cally. Similarly, the actual modulus of elasticity E of the principal timber elements is a largely unknown and somewhat variable factor, but has potential for enhancing performance assessments if true values can be established. While these aspects all provide potential enhancements, it is noted that concealed defects and historical alterations can also have negative influence on capacity. The destructive influence of poorly considered heating and plumbing installations (Figure 4) can 4) can lay hidden from view, but give reductions in capacity. As part of the appraisal, the engineer should consider the past history of a building or structure. Consideration should also be given to required future loading requirements. When looking at historical performance, it is appropriate to ask the following questions:
important that such matters are considered as part of the appraisal process.
• What loads has the structure carried during its life to date? • Are there defects or distress that have resulted from this historical use? • Does the evidence show that the structure has performed adequately?
Load testing The ability to understand this range of factors is critical to the proper assessment of existing structures. To achieve confidence in the capacity of an existing structure, load testing has traditionally been carried out to prove both serviceability and ultimate capacity. In practical terms, the serviceability assessment is often the principal consideration on a historic structure due to the long-span nature of many structures encountered. Tests Tests to destruction would be in conflict with conservation philosophy, philosophy, although in some excep exceptional tional circumstances such tests can yield useful research data. The load applied during a serviceability test should aim to be representative of the real-life anticipated service of the structure. The problem with physical load tests involving the application of static load on historic floors is that they often involve moving heavy materials around buildings with sensitive fabric, so good protection measures are necessary. This is also a labour-intensiv labour-intensive e exercise exer cise and is often limited to a small range of loading configurations.
Magnitude of loading When considering future use, the following questions should be considered:
Design criteria
• Is it intended that the structure should carry additional applied load (variable actions) over and above what it has already been subjected to? • Does its previous performance provide a better justification for its future life than the evidence produced by calculations based on assumed properties?
With historic floors, where beam spans are often relatively large, suitability for reuse is generally defined by limiting deflection criteria, and the influence of true material properties, beam end fixity and stiffness of support is of critical interest. Secondary
It is also important that poor building maintenance is not immediately taken as a reason to place disproportional weight on assumptions of a deficient structure. All buildings require maintenance, and it is
When designing new floor structures, it is perfectly reasonable to reach for an appropriate design standard such as BS EN 19902 and BS EN 19913 and to use the loads specified. Where the floor is existing, the engineer has the benefit of seeing how the floor has performed in its previous existence. If the floor or structure has been shown to perform adequately historically, then this is a relevant consideration. A pragmatic compromise can be reached which represents an appropriately safe situation that avoids unnecessary and potentially intrusive strengthening works. It is usual to consider the load capacity of the floors in terms of strength (the loading which can be supported before a
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TheStructuralEngineer
Technical
June 2016
Non-invasive appraisal
5 Figure Room occupancy
6 �Figure Dynamic floor
equivalent to domestic loading
appraisal in progress
8 Figure Octagonal Gallery, Mount Stewart House
7 Figure Accelerometer data collectors
structural failure occurs) and the deflection characteristics of the floor (which may cause damage to supported finishes and/ or a perception of “liveliness” in the floor). It is generally the case that the first sign of a “problem” is fractures to finishes resulting from deflections, and for this reason a focus on deflection characteristics is the primary consideration. When considering imposed loading, it is useful to present figures to clients in an easily understood format and occupancy is one useful illustration (Figure 5): 5): Average weight male = 84kg; average weight female = 69kg Average loading = 76.5kg = 0.75kN BS EN 1991-1-1 domestic imposed loading (variable action) of 1.5kN/m2 equates to two persons per square metre Office imposed impose d loading (variable (varia ble action) actio n) of 2.5kN/m2 equates to just over three persons per square metre Part 7 of the Conservation compendium, on assessing imposed loads, provides further useful information and illustrations4.
Dynamic assessment Although simple analysis and physical load testing are useful tools available to the structural engineer, the preference should always be to seek non-invasive and lowimpact techniques that could reveal the true in situ performance characteristics of
the structure. The dynamic properties of floors are primarily linked to their natural frequencies and their associated mode shapes. They are dependent on the mass distribution, stiffness and boundary supports. While it is unusual for a floor to change its mass distribution, over time the stiffness can change because of deterioration or damage and the boundary supports can relax. An assessment of the condition can be made by an inspection involving removal of the floor finishes; however, this is inevitably intrusive and often undesirable in heritage buildings. By measuring the natural frequencies and mode shapes, an assessment of stiffness and boundary supports can be made without intrusion. Additionally, the frequency of the first natural mode ca n be checked against the guidelines that apply for certain uses, giving additional qualitative data. The measurement technique involves applying impulses to one location on the floor and measuring the vibration response at a map of locations around the room. The measurements are processed into frequency response functions, which are further processed into the natural frequencies and mode shapes. From this data an assessment of the floor performance can be made. The technique can be extended to give a value for deflection under static loading. This is based on deriving the stiffness of the floor from an estimate of the weight of the
floor and the measured frequency of the first natural mode. From the stiffness value, the deflection under dead loads and live loads can then be determined. Figure 6 shows 6 shows the simple equipment being used to assess a typical floor structure. The equipment is easily transported and data collection on an averaged sized room can be completed in about half a day. A dynamic impulse is applied to the floor at a fixed location and accelerometer data collectors are placed around the room on a standard grid pattern of typically 1m × 1m to record the responses. Figure 7 shows 7 shows the accelerometer sensors used. Analysis of collected data, combined with some basic estimated construction mass information, enables the generation of a three-dimensional (3D) finite-element (FE) structural model, whose characteristics will almost exactly mimic the performance of the floor structure that has been measured, based on matching natural frequencies. This provides structural properties and performance characteristics of the structure and permits assessments to be made of any proposed load cases completely non-invasively and with a high level of confidence. The added benefit of the technique is that any weakness or defect within any assessed structure will be factored automatically into the appraisal.
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43 11 Figure Modal response output of Octagonal Gallery
Case study: Repair of Octagonal Gallery, Mount Stewart House
12 Figure FE model generated from test data to predict performance of Octagonal Gallery
The Central Hall Octagonal Gallery at Mount Stewart House, Northern Ireland (Figure 8), 8), had significant structural movement and had been closed to public access for many years. The gallery was a fully cantilevered structure and had dropped by around 80mm at the balustrade. Investigations revealed significant defects in the floor as a result of historical alterations and damage from inappropriate services insertions which had weakened the principal timber structure (Figure 9). 9). Understanding the structure and how it performed was essential to defining appropriate remedial works. The simple analysis of the cantilever member, member, even without the defects from the notching, showed very little structural capacity and the possibility
that extensive strengthening was necessary. Using dynamic appraisal (Figure 10), 10), the performance of the existing structure revealed significant 3D interaction of the structural elements and how the gallery was performing as a single ring, revealed by the mode shape response (Figure 11) and 11) and the subsequently generated FE model (Figure 12). 12). Although the notching of the joists had weakened the structure and required repair, the i nherent structural form was shown to be adequate. The process of repair and strengthenin strengthening g involved carefully jacking the gallery to close up the notch-rela notch-related ted deflection (Figure 13) and providing simple splint repairs to the notches. All existing fabric was retained and a simple, cost-effective solution was achieved. The gallery was restored to its original configuration and reopened for public access.
Conclusion
Figure 10 Dynamic appraisal of Octagonal Gallery
With existing building appraisal there is a natural tendency for engineers to take a conservative and “safe” approach to evaluation of structures; in many cases, this is a reasonable approach. However, However, where new techniques can be developed to assist in the process of assessment, the benefits to clients and associated heritage protection can
13 Figure Support structure used to lift floor and permit repairs to gallery floor structure notching
be significant. The use of dynamic appraisal enables the engineer to achieve a significantly higher level of confidence in a structure where previously there had been a need to use a combination of experience, engineering judgement judge ment and conser conservati vative ve analysi analysis s using using assumed structural properties. The technique can minimise, or potentially avoid, repairs and ensure that the conservation principle of minimum intervention is achieved.
References
�1
British Standards Institution (2013) BS 7913:2013 Guide to the conservation of historic buildings , London, UK: BSI
�2
British Standards Institution (2002) BS EN 1990:2002 1990:2002+A1:2005 +A1:2005 Eurocode 0. Basis of structur structural al design , London, UK: BSI
Figure 9 Notches from earlier plumbing installation resulting in severe movement to gallery structure
�3
�4
British Standards Institution (2002) BS EN 1991-1-1:2002 Eurocode 1. Actions on structures. Actions structures. General General actions. Densities, Densities, self-weight, self-weight, imposed imposed loads for buildings , London, UK: BSI Hume I. and Miller J. (2015) ‘Conservation compendium. Part 7: Imposed load in historic buildings: assessing what is real’, The Structural Engineer , 93 (6) pp. 40–43
2016
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TheStructuralEngineer
45
June 2016
Opinion Letters or longer articles written from a personal perspective, on topics of current interest interest that offer a particular opinion and often encourage further discussion and/or debate.
46 Pr Profile: ofile: Anne Ann e Fuller 48 Viewpoint: 48 Viewpoint: What do women want? 50 Conservation 50 Conservation compendium. Epilogue: The future futur e of conser conserva vation tion engineering enginee ring 52 Viewpoint: Inspiring the the next generat generation ion 55 Verulam
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TheStructuralEngineer
Opinion
June 2016
Anne Fuller
Profile Anne Fuller has been an Institution chief examiner, has designed challenging buildings all over the UK, and is now director of Capita’s civil and structural engineering division in the North. She discusses her career with Jackie Whitelaw and wonders whether talking to girls at school is really all we have in our armoury in the battle to increase diversity in the profession.
Who remembers this question from the Institution’s Chartered Membership Examination in 2008? To paraphrase: A tank is required in a wildlife centre to accommodate crocodiles. Three islands are required required in the tank on which the crocodiles may roam. Prepare a design appraisal etc. “How likely is that commission going to be?” the author of the question, Anne Fuller, Fuller, was asked at the time she wrote it. Fuller, who became a chief examiner for the Institution in 2004, was then a regular at setting questions. Although she agreed that it was an unlikely thing to find yourself doing as a structural engineer, engineer, the question was deliberately chosen as something unexpected with which to challenge people. How apposite was it then that several years later Fuller Fuller was herself designing a crocodile tank (Figure 1) and 1) and islands as part of a £30M project for Chester Zoo? It turned out to be one of her favourite schemes from her entire 33-year career so far – and, yes, it was challenging! At the time, Fuller was working with AECOM managing the building engineering team in the north of England. But Chester proved to be her last job with the firm and, after over 30 years with the company company,, she left in 2014 to join Capita as its director of civil and structural engineering for the Midlands and the North. She is now engaged in an equally fascinating project – the Defence and National Rehabilitation Centre for charity BS Stanford at Stanford Hall in the Midlands. The facility is being designed to house the latest technology and specialist rehabilitation services for injured servicemen and women and involves 18 new buildings, along with refurbishment of the Grade II listed hall, which houses its own Art Deco theatre. “It is very close to my heart,” she says. “The nature of what we are doing and the people we are doing it for requires that we do our very best work.” It was also one of t he first projects that Fuller bid for and won, with contractor Interserve, in her new Capita role. Stanford Hall has been a catalyst for expanding her team. “We’ve doubled in i n numbers to 40 – 35 at the th e office in Cheadle Hulme Hu lme in Manchesterr and five at a new office in Redditch. Mancheste Reddit ch. It’s very satisfying,” satisf ying,” she says, “and there is much more to come.”
Rising to the challenge After spending three happy decades wi th one employer, Fuller, Fuller, now 54, surprised herself when she decided to jump ship for a new firm. “I assumed I’d never leave. I was approached, which is always flattering, but my first response was no – and then I thought, it’s time!” It was an even bigger decision given she was in the middle of the Chester Zoo project, but she left the work on the islands scheme, with its biodome and treetop walkways for visitors, in capable hands and has since returned to see the finished project. “It was fantastic to work on,” she says, “not least because you had to understand the animals in order
to be able to design accommodation for them. There are macaque monkeys and orangutans in the biodome so everything has to be tamperproof and you have consider how far they can reach! “The islands, each housing animals you would find on different Southeast Asian islands, are joined by a river complete with crocodiles and an underwater viewing area. “The crocodiles stretched my structural engineering skills and I’d never built a river before; or a tiger enclosure for that matter.” Capita was a big attraction because it was a chance for her to lead and grow a small team into a big business and it took her out of her comfort zone of largely public sector work, particularly in university laboratories, healthcare healthcare and education, and full on into the world of commercial property. Fuller is from the North West and loves Manchester, so an extra attraction for joining Capita came from knowing that the firm was a serious player in transforming the city and she would be playing a part in that. “It wasn’t until I was approached that I realised the full extent of the work Capita had been doing, that effectively it could claim to be Manchester’s engineer.” The property and infrastructure arm of the firm has worked on several of the 20 new buildings that make up the £1.5bn Spinningfields business, retail and residential development, the BBC MediaCity at Salford Quays, the Etihad Bridge for Manchester City Football Club (her team), Manchester Metropolitan University’s Birley Fields development, and the refurbishment of the historic pavilion and design of a new conference venue (Figure 2) at 2) at Lancashire County Cricket Club, among many others.
An accide accidental ntal engine engineer er Fuller has worked in Manchester for almost all of her career, apart from a year in the Oscar Osc ar Faber (now AECOM) AECOM ) St Albans office after she
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47 1 �Figure Crocodile viewing area at Chester Zoo
graduated from Leeds University in civil engineering in 1982. She also spent 18 months on site with a contractor at Heysham 2 nuclear power station as part of her professional education. She admits she fell onto the Leeds course. “I’d studied maths, physics and chemistry at school but I didn’t want to focus totally on any of those. Civil engineering was a good bet. I know I didn’t think it through enough and I’d advise my own children to think a lot more. It was by complete good fortune that it was the right t hing for me. “I did always intend to go down the structural engineering route though – Leeds covered both, but I knew what I wanted to focus on.”
2 Figure New stand and historic pavilion at Lancashire Cricket Club
O O Z R E T S E H C
It was the late 1970s when Fuller started studying and if engineering is still not the norm as a choice of career Figure 3 Alan Turing Building, Manchester University for women nowadays it was even rarer back then. As with most women from the era, Fuller is uneasy talking about being a female engineer. “On the one hand I am happy to talk about women in engineering – it needs to be talked about. But I also “Equally,, the assumption that women want something completely “Equally feel uncomfortable – I’ve always been in a minority but never felt I was different from a career than men is unfounded. one,” she says. “I’ve just gone on and done i t.” “Everyone wants more flexible working and sensible working At university her sex was never an issue. “Leeds had a reputation for hours, the right to a safe working environment, decent pay, improved attracting more women, but even so, out of a course of 150, there were job security security,, and a clear clear career career progr progressio ession. n. We We need need to chang change e just 10 of us. But But it didn didn’t ’t matter matter at all.” all.” construction to be a better place for everyone; when that happens it Throughout her career the only blatant sexism encountered was will automatically be a place for women to want to work.” when she was on site with the contractor. contractor. “That was from the senior people. They told me they didn’t want me there because I was a Embracing confrontation woman. That was a bit of a shock, to pitch up on your first day, at 22, Fuller says she has been fortunate in her own career. “I was very and be told ‘we don’t want you’. I’m sure those types of people have all happy at AECOM, otherwise I wouldn’t have stayed. I was always gone from the industry now, but it was a shame because being on the progressing, and always working on interesting projects, such site was a great experience. as designing the Alan Turing Building (Figure 3) at Manchester “I stuck it out though and it toughened me up. And it confirmed to me University for astronomy, maths, physics and photon science, where that I loved engineering whatever the challenges.” vibration issues were key; and Manchester Interdisciplinary Biocentre (now Manchester Institute of Biotechnology), also at the university, where I had to get to grips with the various needs of the research to An industry industry for all be undertaken in the building.” What are her views on women in engineering now? “I appreciate that work is needed to increase the numbers,” she says. “But I feel resentful Now her focus – and pleasure – is on developing her team at Capita and continuing to design and deliver projects. If there is a that we have to do that by singling women out. We need to get to a point when being a woman in engineering is not special.” downside, it is all the HR paperwork – “it’s very time-consuming and I am sure it can’t be cost-effective to have me doing it.” She is unimpressed that the main weapon in the industry’s armoury is still to focus on going into schools to talk to girls about careers in Her management style, she says, is inclusive rather than dictatorial. She has never been put off her stride by the confrontation that construction. “I agree it is valuable – I do it myself – but I can’t help thinking, is this is a natural part of the construction business – that Heysham 2 experience has stood her in good stead. “Everyone is under the best we can come up with? Instead of trying to change the views of women so that they are prepared to consider a career in construction, pressure, budgets are tight, so confrontation is inevitable. My advice is to say your piece, hold your ground and keep it to the meeting shouldn’t we be trying to change construction to make it an industry women want to enter and, just as importantly given the poor retention room. The rule is to make sure you can still be friendly with the team rates, to stay in? outside of that room.”
L E E P E K I M
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TheStructuralEngineer
Opinion
June 2016
Women in engineering
Viiewpoint V What makes an engineering practice attractive to women, asks Margaret Cooke of Cooke of Integral Engineering Design. Could it just be a happy, healthy, friendly and flexible workplace that appeals to everyone – regardless of gender?
What do women want? I had dinner a few months ago with some of the illustrious members of the Institution’s Institution ’s History Study Group and we fell to talking about the state of “women in engineering”. I mentioned that, at Integral Integral,, 50% of our technical staff are women, despite the average across the industry being considerably lower. Expressions of surprise and delight followed, with a discussion on why that should be – what is it that we do as a practice which makes it easy for us to recruit and, more importantly, retain our female staff? It is terribly easy to sound “holier than thou” when discussing these things: this article is simply a reflection of our experience and the things that have worked for us.
The major difference came, as you might expect, later in people’s careers. We genuinely embrace part-time working – for us part-time does not mean undercommitted, it means that we can afford more brilliant engineering brains. And because those brains are, perhaps, working a three- or four-day week, if you need extra days for a short period of time then often
"THIS ARTICLE IS SIMPLY A REFLECTION REFL ECTION OF OUR EXPERIENCE AND THE THINGS THAT HAVE H AVE WORKED FOR US"
A flexible approac h We canvassed our female staff to discover whether there was anything in particular about our practice which they felt made it more attractive to them. Generally, the things which motivated our younger engineers were exactly those which motivate any young engineer: good career path, i nteresting wor k, suffi cient remuneration, good training. Interestingly, having role models in the form of female directors and associates was not something they put high on their list (although, (although, for my own ego, I like to think that it sends a subtle yet important message!)
this can be accommodated. Obviously, we pay the extra or give time off in lieu – but as a practice we have the potential for greater flexibility than a wholly full-time workforce would give us. Clearly, this offer of flexibility is not confined to the female members of staff, but until the world changes more profoundly (and let’s hope that this is happening), then the current users of this flexibilit y in our offi ce happen to be female.
A matter of confidence More personally, I observe that (forgive the
sweeping generalisation) women tend to express themselves differently from men. When we pick up graduate engineers we also pick up 25 years of cultural expectation.. Ask a woman if she can do expectation a task and she will hesitate, say she will give it a go, leave you with the impression that she is likely to mess up badly, and then complete the task with brilliance in half the time you expected. Ask a man and they will tell you with a high degree of confidence that the task is no problem. This may be true, but if they then get stuck it is that bit harder to ask questions. There is nothing wrong with either approach – they are just very different. If you, as a manager, accept the first answer from the woman then you are likely to label her as under-confident and potentially less good than her male colleague. I wonder how many women and their managers have fallen into this trap? The lesson goes both ways, of course: women engineers have to have confidence in their ability and get rid of the false modesty; male engineers have to feel that it is allowable to say you don’t know how to do something. We have two rules rule s in our ou r offi ce: • there are no stupid questions • if you get stuck for more than, say, 15 minutes then you have to ask
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Collaborative working The last thing I note is that we work collaboratively a cross the offi ce. Problems are shared. Teams are loose so that, while each person feels individually responsible for their projects, they know that if there is an issue they will always have back-up from the rest of the offi ce. Early advice and early sense-checking are encouraged so that small problems do not become big ones. We work for the collective good of our clients and for each other – financially and socially. We don’t monitor every project in financial competition against the next, although we know which are doing well and which need support. My suspicion is that this very gentle monitoring of performance is conducive to better productivity all round and suits those
"IF YOU DON’T SET COMPETITION BETWEEN TEAMS,, THEN OVERAL TEAMS OVERALL L YOU END EN D UP WITH WIT H A HAPPIER, HEALTHIER AND MORE MO RE FRIENDLY FRIE NDLY WORKPLACE"
performing to the best of their ability. If you don’t set competition between teams, then overall you end up with a happier, healthier and more friendly workplace. Is this what attracts our female engineers? I am not sure – but whatever it is, it appears to be working for us.
Author Aut hor biogr biograph aphy y Margaret Cooke
BSc (Hons), CEng, MIStructE, Conservation
who enjoy working collaboratively. If you know that your time spent giving advice on someone else’s project can be put down to “training”, then overall we will perform better. Perhaps this suits a team of people, male and female, who enjoy each other’s company and delight in seeing everyone
Accredited Engineer Margaret is a Director at Integral Engineering Design Ltd. She specialises in conservation work and has just completed the multi-award winning Middleport Pottery project.
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TheStructuralEngineer
Opinion
June 2016
A bright future
Conservation compendium Epilogue: The future of conservation engineering
This article forms part of the Conservation compendium, which aims to improve the way engineers handle historic fabric through the study of historic materials, conservation conservation philosophy, forms of constructi construction on and project examples. Articles in the series are written by Conservation Accredited Engineers. The series editor is James Miller.
James Miller brings Miller brings this series to a close by looking back over ground covered and forward to a bright future in which conservation accreditation is increasingly valued and engineers are able to innovate through the application of emerging technologies. The Conservation compendium began in January 2015 and ends this month. Over that period it has covered subjects as diverse as the scaffolding of historic buildings1, the development of loading2, the appraisal of ruins3 and the assessment of filler-joist floors 4. The authors hope that it has been of practical use. One aim of the series was to provide a perspective on conservation and, through the subject matter, matter, to equip engineers with at least some of the attributes necessary to become accredited in conservation. During the past 18 months, the Conservation Accreditation Register for Engineers (CARE) has seen a tangible rise in the number of applications. It seems that the series has borne fruit. At the same time, the designation Conservation Accredited Engineer has continued to make a strong advance in the UK. It is now mandatory for certain projects in Northern Ireland and requirements for assessment of various historic works by a CARE-registered CARE-register ed engineer now regularly appear in planning conditions. That, along with the acknowledgement of the Register in BS 79135, is reassuring for the future.
1 Figure Although heavily corroded, the majority of ironwork to these cantilever trusses was retained during the restoration of Tynemouth Station
and is the challenge of the specialism. To achieve this we must understand how the structures were built, the materials used and be gentle in making changes. We must adhere to the principles of the Burra Charter 6 and Historic England’s Conservation Principles7: minimising intervention, aiming for reversibility,, keeping faith with original load reversibility paths and materials where possible (Figure 1). 1).
Sensitivity, excellence and innovation Conservation engineers, of course, take to their subject as a mark of their passion for historic fabric, just as those engaged in highrise have a passion to build taller, faster faster and more efficiently. There is a clear path pat h and this has emerged through the series: Sensitivity To work with historic fabric and, in many cases, leave little mark is essentially a vocation. It is learnt through commitment. This is largely what other heritage professiona professionals ls expect
Excellence To practise in the field of conservation requires a deep understanding of materials, load factors, risk, stiffness and redundancy – all these being attributes key to the discipline of structural engineering. Most historic structures protected by heritage legislation do not conform to modern codes; the engineer needs to know exactly why they stand up and what is likely to happen when change is introduced. They must diagnose defects with confidence.
Innovation Working with new buildings is, in one sense, easier than with old ones. In a new building the engineer knows largely how the fabric will perform because they designed it in the first place; in an existing building there may be very many unknowns. This provides much of the challenge for innovating in the discipline – in survey,, assessment, monitoring and modelling survey – and it provides a largely untapped area for engineers to exploit as Building Information Modelling (BIM) initiatives take further ground over the next few years (Figure 2). 2).
New initiatives Some of the articles in the series have touched on relevant and developing technologies. Laser scanning has penetrated most aspects of surveying and the point cloud is now at the disposal of the engineer at almost no additional charge: all that is required is to learn to manipulate and thin the mass of data before
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51 2 Figure In the recent analysis of the Iron Bridge, point-cloud data was used to model unique element geometry and crack defects
Becoming Conservation Accredited Find out more about becoming a Conservation Accredited Engineer at the following links: ICE website www.ice.org.uk/careers-and-professionaldevelopment/careers-advice-for-civilengineers/specialist-professionalregisters
D N A L G N E C I R O T S I H & L L O B M A R
inserting it directly into Revit® or another relevant modelling platform. Airborne lidar surveying has become common, as has the use of drones for inspection and recording. The use of laser scan overlays for the measurement of movement movement is also now familiar, as described by Ed Morton in his article on monitoring8, together with current research into satellite monitoring. Jon Avent looks at signature monitoring of vibration elsewhere in this i ssue (page 40). 40). The use of BIM as a tool for modelling and managing historic portfolios is perhaps an area for development. Geometries harvested from point-cloud data through the scanning process can be very helpful in setting up inventories of parts for historic fabric. They can help create an intelligent database which can be interrogated through a threedimensional interface.
How to become Conservation Accredited We conclude with a reminder of the accreditation process. The Register is supported jointly by The Institution of Structural Engineers and Institution of Civil Engineers; details can be found on both institutions’ websites or through the CARE website (Box) (Box).. Applicants must be Chartered and demonstrate key attributes in a number of areas through submission of case studies, statements and evidence of continuing professional profession al development (CPD). There is no doubt that the existence of the Register has encouraged many people to formalise a specialism they have been pursing for some time. We trust that the series has helped focus on just some of the fascinating forms of construction and the thought processes necessary to enact change. This puts the UK’s engineers among the best in the world in their understanding and handling of historic, protected fabric.
Authorr biograph Autho biography y JamesMiller MA, CEng, FIStructE, FICE, Conservation Accredited
Engineer James Miller is Consultant for Heritage at CTP Consulting Engineers and has been in practice for over 30 years. His experience includes the stabilising of settlement in Westminster Hall, facilities at Wells Cathedral, the restoration of Tynemouth Station and an assessment of the Iron Bridge.
IStructE website www.istructe.org/about-us/ www.istructe.org/ about-us/organisationorganisationstructure/subsidiary-organisations/ conservation-accreditation-register-forengineers CARE website www.careregister.org.uk
References Ruddy J. (2015) ‘Conservation Compendium. Part 12: Scaffolding of historic structures’, The Structural Engineer , 93 (11), pp. 40–44 � 1)
Hume I. and Miller J. (2015) ‘Conservation compendium. Part 7: Imposed load in historic buildings: assessing what is real’, The Structural Engineer , 93 (6), pp. 40–43 � 2)
Aventt J. (2015) ‘Conservation compendium. Part 11: Aven A career in ruins (the challenges presented by derelict structures)’, The Structural Engineer , 93 (10), pp. 38–42 � 3)
Miller J. (2016) ‘Conservation compendium. Part 17: Filler-joist floors – development, capacity and typical defects’, The Structural Engineer , 94 (5), pp. 44–47 � 4)
British Standards Institution (2013) BS 7913:2013 Guide to the conservation of historic buildings, buildings, London, UK: BSI � 5)
Australia ICOMOS (1979) The Burra Charter (The Australian ICOMOS Charter for Places of of Cultural Significance) [Online] Available at: http://australia.icomos. org/wp-content/uploads/BURRA org/wp-cont ent/uploads/BURRA-CHARTER-1999 -CHARTER-1999_charter_charteronly.pdf (Accessed: May 2016) � 6)
English Heritage (2008) Conservation Principles, Policies and Guidance [Online] Guidance [Online] Available at: https://content.historicengland.org.uk/imagesbooks/publications/ books/ publications/conservation-princi conservation-principlesplessustainable-management-historic-environment/ conservationprinciplespoliciesguidanceapr08web.pdf/ (Accessed: May 2016) � 7)
Morton E. (2016) ‘Conservation compendium. Part 16: The monitoring of movement in historic buildings and structures’, The Structural Engineer , 94 (4), pp. 39–42 � 8)
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Opinion
June 2016
Inspiring the next generation
Viiewpoint V In this article Philip article Philip Isaac, Dan Bergsagel and Sinead Conneely propose Conneely propose small, short, local design-and-build projects as an effective means of engaging students with engineering, and as a process which all members can get involved in.
Inspiring the next generation Where Whe re are all the eng engine ineers ers? ? The UK and many other countries around the world are currently not training enough engineers to meet the skills demands of the future. A recent survey of business leaders showed that over half could not find the employees they wanted, and 59% believed that the shortage of engineers was a significant threat to their businesses1. One estimate puts the shortfall of engineers produced at 55 000 each year, almost twice the current rate of training in the UK1. A concerning indicator is engineering’s low rank among preferred careers for schoolleavers. A comprehensive survey compiled by the Education and Employers Taskforce in 2013 showed that just 2.5% of 17–18-year-olds were considering careers in an engineering discipline (civil, mechanical, electrical)2. This is with the engineering sector contributing an estimated 27.1% of UK GDP3.
Whydo we we all all look look the sam same? e? The House of Commons Select Committee on Science and Technology has raised concerns about both gender equality and ethnic diversity in engineering fields4. It is claimed that there are still more than eight times as many men as women in the engineering sector5. This sustained lack of diversity could be damaging to business, as well as being ethically and legally questionable6. Many factors contribute to the careers people pursue, but our experiences at school play an important role. Until 2013, careers services for 16-year-olds in the UK were provided by external specialist organisations. Since 2013, this responsibility has been transferred transferr ed to cash- and time-strapped schools themselves. This has left schools
with an impossible task: to convey information about all professions to all students, debunking as they go stereotypes and prejudices about professions like engineering. Even students who do want to be structural engineers often have little opportunity to garner experience of the profession before applying to university. This lack of exposure to the industry is perpetuated in parts of society which are currently underrepresented underrepresented within it, and can be detrimental when it comes to interviews and writing personal statements.
Whatt are Wha are we we curr current ently ly doing doingabou aboutt it? it? In this context, encouraging young people from all backgrounds and genders into the profession is a crucial goal which we are failing to achieve, despite a concerted industry effort. The industry supports large-scale schemes, and organisations such as STEMNET, the Big Bang Fair UK and Tomorrow’s Engineers. The Royal Academy of Engineering’s “Ingenious” public engagement awards underwrite many excellent excell ent projects, like the British Science Association’s “Engineers: Engage!” and Open-City’s Structure Rocks!”. Professional institutions and university departments nationwide invest resources into inspiring potential young engineers. These are popular events which are built around easily repeatable activities. However,, while reaching large audiences, However the participants are often from self-selecting groups, and are consequently not always those underrepresented in the sector. While acknowledging the fantastic work done, the Commons Select Committee highlights three issues which are holding engineering development back: misconceptions in the perception perceptio n of engineering, engineering , insufficient careers “
advice, and under-engagement of local employers with schools7.
Whatt more Wha more cou could ld we we do? do? We believe more can be done to encourage students to consider careers in engineering; in addition to broad initiatives, members could adopt a localised approach in their community. We propose supplementing the current nationwide approach with short, focused, local interventions to provide students with a holistic insight into the construction industry in a fun and creative way. Here, we describe and appraise a simple collaborative venture to run a two-day designand-build workshop at BSix Sixth Form College in Clapton, London, which culminated in the construction of a winning student design in the college garden (Figure 1). 1).
Pavilion Project, Clapton We learn best from doing. To discuss engineering in the context of something tangible that the students could see and understand, we developed a local project brief – the design and construction of a small pavilion to be located in the grounds of their college, and built together by us and the students. We prepared a project brief with restrictions on building area, height, available materials and, most crucially, complexity – it was important to stress that construction of the pavilion would be achieved by unskilled workers with limited equipment in a short space of time. Over two days the students dissected the brief in groups (helped along with four lectures on relevant topics), with the end of the workshop marked by presenting their work through a design critique to
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53 1 �Figure Completed pavilion in college garden
I O H C A C I R E
2 Figure Students presented their
3 �Figure Model making helped
work to industry professionals
visualise the design
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industry professionals (Figure 2). 2). The students were given an insight into the design process by developing the concept and design for a pavilion on a site they were familiar with (their own school) and to fulfil a function they felt was undercatered for (their leisure time at college). The local focus of the project meant the students were in the unique situation of being the client, the designer, the main contractor and the end-user. By designing and helping to build a structure which they w ill use for the year to come, they experienced the satisfaction every structural engineer has in contributing to our built environment.
What worked? worked? Using local buildings as case studies to discuss architectural and engineering design drivers in a simple way. Familiarity with structures like St Paul’s Cathedral, 122 Leadenhall Street and the London Eye meant we could discuss how different they might look without certain design constraints (e.g. cost, available materials, site topology and planning restrictions). Would St Paul’s Cathedral have two redundant domes with a tighter budget? Would 122 Leadenhall Street be cheesegrater-shaped without St Paul’s? Would the London Eye be the largest cantilever viewing wheel if the River Thames wasn’t in the way? Focusing on model making and drawing production to clarify the design process. Being able to visualise a design (Figure 3) and draw it clearly made it much easier to persuade a jury of its buildability. The drawing process helped the students grapple with the design constraints much more effectively than any guidance from us did.
R E K O O H S E M A J
Dividing the participants into small multidisciplinary design groups. Incorporating art BTec students with maths and science specialists gave them a safe environmentt to produce creative designs, and environmen the skills to develop and present them. Motivating students with a friendly competition. Providing a goal to aim for – the mini-critique to a prestigious panel of industry professionals – produced inspiring results. The students worked constantly through all available breaks, and presented their work with more poise and belief than many of us would manage now. Trusting the students to design the pavilion. Wisely or not, we had committed to building the winning scheme – designed by them and built with them (Figure 4). 4). This token gave them the confidence to engage with the t ask. It demonstrated that we believed they could all succeed as engineers.
Whatdidn didn’t ’t work? work? Doing it all in less than three weeks. To fit in with the AS-level calendar, we completed the workshops, design and construction of the pavilion in two-anda-half weeks, working around full-time employment to design the pavilion on a Wednesday evening, consult with carpenters on a Thursday evening, produce construction drawings on a Friday morning and build the pavilion over the following two weekends. While this seemed necessary to match the school’s schedule, and was certainly
exhilarating, the speed of the initial exhilarating, i nitial design meant more had to be resolved during construction under time pressures. There should be no reason to try and condense the project into such a short space of time unless you enjoy waking up with the dawn chorus at the weekend to go to site by choice. Pre-ordering materials. In addition to the design implications, the short programme meant that the procurement of the core bulk materials had to be arranged prior to the workshop. While the pre-order pre-ordered ed material provided a useful constraint for the brief, it also led to a necessary surplus of material for the final design. This led to project waste.
Is it worth your time? Small-scale, focused, local interventions like this one can be time-consuming and exhausting. Compared to the numbers of young people that the national-lev national-level el outreach events reach, they may seem a poor return on time, money and energy invested. So, is it worth it? We believe it is. We witnessed first-hand how engaged the participants were, hailing from all backgrounds and each with di fferent ambitions. By finding the school and coopting its students – as opposed to readymotivated students finding us – we can ensure we access hard-to-reach groups of young students. By focusing attention on one local intervention at a time, we can provide students with a prolonged period of contact with young professionals profession als in the industry industry.. During the period working together, we saw the participants
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Opinion
June 2016
Inspiring the next generation
References �1) The Economist (2015)
Mind the gap [Online] Available at: www.economist. com/news/britain/21648003-lackskilled-workers-and-managers-dragscountry-down-mind-gap country-do wn-mind-gap (Accessed: May 2016) �2)
I O H C A C I R E
Mann A., Massey D., Glover P., Kashefpadkel E.T. and Dawkins J. (2013) Nothing in common: The career aspirations of young Britons mapped against projected labour market demand (2010-2020) [Online] Available at: www.educationandemployers.org/wpcontent/uploads/2014/06/nothing_in_ common_final.pdff (Accessed: May 2016) common_final.pd
�Figure 4 � Students finished by building the winning scheme
grow in confidence, with perceived gender,, class and racial barriers gender to architecture and engineering tumbling. Projects like these can be immensely rewarding for the students, but also for those organising them. They provide an opportunity to teach, design, manage and build, on a small, manageable scale and on one’s own terms. For the organisations that support the venture (the schools, the material suppliers, the engineers, the contractors), it is an opportunity to develop industry links and give back to their local community.
�3) Engineering UK (2015)
Engineering UK 2015: The state of engineering [Online] engineering [Online] Available at: www.engineeringuk.com/ EngineeringUK2015/EngUK_ Report_2015_Interactiv Report_2015_I nteractive.pdf e.pdf (Accessed: May 2016) �4) House of Commons Science
I O H C A C I R E
A call to arms
Acknow Ack nowledg ledgeme ements nts
The enthusiasm of the students during the build and the manner in which they prepared for the critique was fantastic. The completed pavilion situated in the college garden acts as a daily reminder to the student cohort of their endeavours. It seems clear that, given the opportunity and resources, there are many enthusiastic young adults from diverse backgrounds ready to join the industry and help us meet our future skills demand. There are countless different local design-and-build design-andbuild projects which could be run, and by necessity each one should be tailored to the interests of the students and the nuances of the site. However, what we hope this project demonstrates is how simple, rewarding and effective small, local interventions can be in augmenting the current gamut of public engagement and outreach schemes that thousands of Institution members are already engaged in. Our experience was one of enormous satisfaction satisfactio n and pride at seeing so many young people excited by the things we do every day. Our aim is that sharing this excitement might act as a call to arms for other members to take up projects in their community in the same spirit.
Financial support for the Pavilion Project was kindly provided by AKT II, with free labour donated by Conneely Dry Lining and materials provided at reduced prices/for free by Home Build Supplies/Transport Supplies/Transport for London. Thank you to BSix Sixth Form College for its support and cooperation in organising the workshops and the build. Special thanks to the panel of jurists: juris ts: Asif Asif Khan, Khan, Cyril Cyril Shing Shing,, Ed Mosel Moseley ey and and Jeroen Janssen; and to architect Ishbel Mull for her help in organising the workshops.
and Technology Committee (2013) ‘Chapter 2: The engineering skills gap’, In: Educating tomorrow’s engineers: the impact of Government reforms on 14-19 education [Online] education [Online] Available at: www.publications. parliament.uk/pa/cm201213/cmselect/ cmsctech/665/66505.htm (Accessed: May 2016) �5) Sanghani R. (2015) Male-dominated
engineering has an 87 per cent gender gap - but it it pays pays pretty pretty well well [Online] [Online] Available at: www.telegraph.co.uk/ women/womens-business/11692996/ Women-In-Engineering-Day-Gendergap-in-male-dominated-industry-falls. html (Accessed: May 2016) �6)
If you would like more information, or are interested in organising and running a similar workshop at a school near you, images, lecture notes and resources from the project are available for free at https://scalerule.org/ education/pavilion-project-bsix-2015/ .. education/pavilion-project-bsix-2015/
Royal Academy of Engineering (2016) Why is diversity important? [Online] Available at: www.raeng.org. uk/policy/diversity-in-engineering/whyis-diversity-important is-diversity-i mportant (Accessed: May 2016) �7) House of Commons Science
Author Aut hor biogra biographie phies s Philip Isaac MEng, PhD Dan Bergsagel MEng, MA (Cantab) SineadConneely BEng, MSc
Phil, Dan and Sinead are structural engineers interested in teaching design and learning through the process of doing. By day they work at AKT II in Clerkenwell, London; in their spare time they engage with small community education projects as part of Scale Rule (https://scalerule.org/).
and Technology Committee (2013) ‘Chapter 4: Inspiring the next generation’, In: Educating tomorrow’s engineers: the impact of Government reforms on 14-19 education [Online] education [Online] Available at: www.publications. parliament.uk/pa/cm201213/cmselect/ cmsctech/665/66507.htm (Accessed: May 2016)
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Opinion
TheStructuralEngineer
Letters
June 2016
Ve V erulam
55
Send letters to… All contributions to Verulam should be submitted via email to:
[email protected]
Contributions may be edited on the grounds of style and/or length by the Institution's publishing department.
Topics of importance openly discussed
Advent of computer design Cliff Billington MBE writes in with some of his early experiences of computers in designing engineering components. The recent issue concentrating on computing in structural engineering (March 2016) got me thinking a bit. In the early 1970s, I was working as Chief Designer with a major manufacturer of prestressed hollow-core hollow-core flooring units. The design of these lent themselves to some sort of automation, so I taught myself COBOL, a computer language intended for finance and not really aimed at structural analysis. It did, however, enable me to write programs, inputting data via punchcards, which were then run on the company’s mainframe computer, computer, the size of a small room. The success of this venture persuaded the company to invest in a desktop machine with 8k of memory and a dot-matrix printer, at a huge cost. This used BASIC language and was an amazing leap forward in design tools. Younger members of the Institution will not have a clue what I am talking about. Fast-forward some 40 years, however, and all has changed. With the advent of simple spreadsheets,, anyone can produce effective spreadsheets analysis tools to suit specific needs. The need for mental ability to design should not be lost, however, however, by turning to the keyboar keyboard d for everything. I managed a full career producing many complex structures and buildings with no need at all for finite-element analysis, or indeed any sophisticated software tools. A full-page advertisement for software in the issue showed the outer envelope of the SSE Hydro in Glasgow, consisting of large ETFE pneumatic panels. I designed all the connections for these “by hand”. Some of the connections were complex, with up to 24
bolts resisting equally complex loadings. It was quite refreshing to turn to my old textbooks to remind myself of some of the theories, before putting pencil to calc-sheet. I have always had a slight distrust of complex analysis software, which does not give the user a feel for what is going on. I am reminded of my mentor in the early days of limit-state design and CP110, of which he was an author. He used to look over my designs and say, “It’s “It’s all very well, but does the concrete know it’s supposed to be doing this?” Perhaps a slightly naive view, but a question that remains unanswered to this day. It’s always nice to receive reminiscences about how things used to be. But Verulam is sure Cliff would agree that computing doesn’t have to be about “complex analysis”. It can equally be about faster and automated routine design, just to save cost.
Divided responsibilities Regular correspondent, Alasdair Beal (no friend of the Eurocodes!), writes in to assist Andrew Dawber with his recent queries.
The answer to all the interesting conundrums posed by Andrew Dawber (Verulam, April 2016) can be found in BS 449 Appendix E.4 and BS 5950-2 Appendix B5, which both state: “dimensioned shop drawings or details should be submitted in duplicate to the steelwork designer who should retain one copy and return the other to the steel suppliers or the steelwork contractor with any comments”. The National Structural Steelwork Specification for Building C onstructio onstruction n (NSSS) section
3.6 spells out this requirement in more detail: although the fabricator designs the connections, the consulting engineer must check that the fabricator has interpreted the design drawings correctly and provided connections which are structurally adequate and compatible with the frame design. Some may see this as unnecessary but, in reality, it is an essential part of the design process, “closing the responsibility loop” and allowing the design engineer to ensure that the connections are compatible with the frame design and vice versa. Andrew’s list of possible problems is a timely reminder of the issues which can arise if this is not done. No matter how clever the design and calculations for a steel frame are, without connections it is just a heap of metal pieces. In some cases, a quick check by the design engineer that the fabricator’s connection designs look OK could make the difference between safety and disaster. Unfortunately, Eurocode 3, unlike previous codes, treats the design of “joints” (Part 1-8) as a separate subject from the design of “buildings” (Part 1-1). This is a big mistake which can only encourage the attitude among engineers about which Andrew complains. It is also part of the reason for the web buckling problems discussed in Verulam (January, February and March 2016): is the end of a beam on a simple bearing a “joint” or a “member”? EC3 1-1 does not cover this common situation at all, so the engineer has to try using the guidance for column webs in EC3 1-8 (which gives conservative results) or else to follow David Brown’s advice (February 2016) and explore some very complicated clauses in EC3 1-7 (“plated structures subjected to outof-plane loading”). I hope that the committees responsible for revising EC3 will consider putting the design of members and connections back t ogether again. While they are at it, can we also have a practical, economical method for the design of steel beams on simple end bearings?
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Opinion
June 2016
Letters
Alasdair draws attention to the NSSS (as did Verulam in May). One aim of the NSSS is to make contractual responsibilities clear. Alasdair is surely correct in asserting how essential it is for main designers to agree that as-designed connections fulfil the overall design objectives.
Robert Atkinson also replies to Mr Dawber’s letter. Robert reminds us of a lesson that everyone should understand, but that seems often overlooked. Any experienced steelwork contractor contractor will advise that a “least-weightt design” may not be least “least-weigh cost and its adoption frequently spells trouble. With today’s strong steels and efficient design, design , deflection demands demand s and the ability to make connections become ever more important design aspects to consider from the outset.
Mr Dawber’s contribution raises interesting issues. It is my long-held opinion that the lead consultant must retain overall responsibility for their design, and it is not good enough to blame sub-consultants when matters go amiss. The fundamental problem of competitively subletting steelwork design is that the successful scheme will be a minimum-weight solution and, more likely than not, have greater deflections than its competitors. A consultant’s design may well be more robust with any “additional” cost lost within myriad other items. I present two examples concerned with the investigation of failures where competitive designs went amiss, both involving very large portal-framed buildings. The first had a “hitand-miss” frame designed “down to the bone”. The complex deflection patterns resulted in leaks at the laps in the roof cladding. The other was a factory building, again to a minimumsteel design, where overhead cranes were to be laser controlled. Deflections resulted in the system being partly inoperable. The designs for these schemes probably complied with current codes and it could be argued that, in both cases, the brief was at fault. It may be that portals were not necessarily the appropriate solution. In competition a contractor will invariably offer no more than to comply with the brief. This may not always give the required outcome. In my limited experience of Private Finance Initiative schemes, a similar situation appertains. To summarise, the lead engineer has to keep control of the whole process and minimum cost is not necessarily best value! Verulam is sure there are many more Verulam salutary tales out there. If we are all to
become better all-round designers, lessons must be learned!
We all learn best from real-life examples exampl es and Simon Goodman provides some real feedback.
I read with interest the recent item on split responsibilities between the engineer who designs a steel frame and the fabricator who is asked to design the connections. I spent my first 10 years training and working with a commercial steel company and found that we would be responsible for connection design on maybe 60–70% of projects. At the time, this seemed a natural thing to me and, invariably, we might gain a commercial advantage in doing so; 10 minutes’ fabrication time saved on multiple connections could save hundreds or even thousands of pounds. Having moved on to general consultancy practice, I still find I design the main connections as I feel this i s fundamental to my design philosophy. The purpose of this letter, however, is to raise the question of split design responsibility, especially on residential projects which seem to carry the highest risk-to-reward risk-to-reward ratio. I have been brought up to design the steel frame, supporting joists, pad stones, piers, walls – in fact everything structural on the project – and to detail this in such a way that a competent contractor can build the works. R ecently ecently,, I have been asked by several contractors to “finish” the engineer’s design due to caveats or inadequacies in the design. Clearly, as a member of the Institution I am unable to criticise the design, which is often frustrating and sometimes completely infuriating! I offer three recent cases: the first where the side of a two-storey house was being removed and a steel beam installed to carry the roof, wall and joists. The beam was applying a 5t bearing load at the supports, which at one end comprised a 300mm length of cavity wall split on one side by a door and the other by a window. The wall itself was specified as having a central vertical damp-proof course cut through the outer skin. I called the designer, who saw no problem in the design but agreed to build a solid engineering brick pier in front of the wall. “But the client doesn’t want a pier,” he said. Well, he certainly didn’t want the roof on his head either! The second case involved the construction of an open-plan, modern, architect-designed house. The structure was steel-framed with a simple structure, but with no reference as to how stability was achieved; there was a caveat on the engineer’s drawings stating the floor joists and stud walls were to be designed by the contractor. There was no reference to lateral loadings, connection requirements or
any form of design philosophy whatsoever, whatsoever, but clearly the engineer was asking the contractor to design the timber frame to provide lateral stability to the structure. In the third case, the ground-floor rear wall of a house was being removed to make way for a large glazed garden room. The glazed rear wall and sliding door were supported on a simple goalpost frame designed by the engineer with small SHS pinned base posts supporting a small eaves beam via a dubious fin-plate connection; no doubt the inherent stiffness in the pinned base and a nominal factor of safety in the design would have meant the frame would just about work if the architect had not then offset the posts by 200mm (yes, out of the plane of the frame!) and added a caveat that the resulting thermally broken connection should be designed by the builder! Was the engineer aware his goal post was no longer as designed and was the contractor aware he was about to design a critical moment connection? My concern with all these cases is that if there is a subsequent failure, who is responsible? responsible ? In my mind, if I am the engineer, I am responsible for the design and any loss due to a defect in my design renders me liable. In case 1, clearly if we had not intervened by calling the designer, there would have been a problem and they would have been liable; however,, what happens in case 2 if the steel however frame moves because the timber walls have not provided adequate restraint? Again, I would say the engineer is liable for not clarifying their design philosophy and completing the “full design” as they should. But case 3 really is a worry: the engineer’s design, although dubious, probably works; but they are not aware of the posts being moved and the contractor does not realise the importance of the connection because, again, there is no design philosophy. Surely as experienced structural engineers we are responsible for designing the entire structure? If you can only design in steel, don’t take on projects requiring extensive assessment of timber and masonry elements in the hope you can pass responsibility on to others. If you are unable to undertake the full design because the fee is too low, don’t take take the project on in the first place. Robert Atkinson’s letter echoes the same theme, i.e. that professional engineering requires one guiding hand to take responsibility for defining the overall load paths, the overall provisions of stability and robustness: defining how the structure will stand up and assuring every aspect is compatible with that. There is a place for subletting component design, but only when the parameters are fully defined in a manner that reflects the overall design intent.
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TheStructuralEngineer June 2016
At the At back The home of diary dates, updates on Institution services and other miscellanea, plus products, services and jobs.
58 Diary 58 Diary dates 59 Spotlight 59 Spotlight on Structures 60 And 60 And finally… 61 Pr Products oducts & Servi Services ces 63 Services 63 Services Directory 64 TheStructuralEngineerJobs 64 TheStructuralEngineerJobs
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TheStructuralEngineer
At the back
June 2016
Diary dates
Diary dates Note that more current information may be available from the Institution website: www.istructe.org/ www.istructe.org/events-and-awa events-and-awards rds
MEETINGS AT HQ 47–58 Bastwick Street, London EC1V 3PS, UK Thursday 9 June Managing assets with digital engineering Tim Stidwill, Herman Ferreira, Tony Nicholls, and Chris Brock Registration: 17:30; start at 18:00
Wednesday 15 June Gold Medal address 2016 Robert A. Halvorson Registration: 17:30; lecture: 18:00 Lecture: free to attend (registration required); dinner: £70
HISTORY STUDY GROUP 17:30 for 18:00 Tuesday 14 June Historic gasholders in Italy Barbara Berger
REGIONAL GROUPS
Surrey Lancashire and Cheshire Tuesday 21 June Design of Manchester Engineering Campus Development Greg Hardie Arup, 6th Floor, 3 Piccadilly Place, Manchester M1 3BN 17:30 to 20:00 Contact: meetings@ istructe.com Secretary: Ian Tickle (email: ian.tickle@nuvia. co.uk)
South Eastern Counties Thursday 23 June The Canterbury Forum – Ancient Buildings of Hythe Andrew Mills Kent and Canterbury Club, The Elms, Old Dover Road, Canterbury, Kent CT1 3JB 19:00 for 19:30 Secretary: Eric Li (email:
[email protected])
Sunday 3 July The Weald and Downland Open Air Museum Singleton, Chichester, West Sussex PO18 0EU Meet: 13:00 at café kiosk (tour starts at 13:30); museum opens at 10:30am to public Price: £10.50 for adults and £4.40 for children aged 4–15 Email: nwestwood@swh. co.uk Book before 17 June 2016 at: www.eventbrite.co.uk/e/ the-surrey-regional-groupsummer-event-2016tickets-24201578573 Secretary: Ruslan Koutlukaev (email:
[email protected])
Thames Valley Thursday 16 June CDM 2015 Dr Mike Webster Copthorne Slough-Windsor, Cippenham Lane, Slough,
Unless otherwise stated, technical meetings start at 18:00 with refreshments from 17:30 - they are free of charge to attend, unless stated otherwise. Registration for evening technical meetings is required via
[email protected] History Study Group meetings start at 18:00 with refreshments from 17:30. Registration is not required for History Study Group meetings except for the Annual business meeting held in January.
Regional Group Committee members should submit details of forthcoming events to:
[email protected]
Berkshire SL1 2YE 18:00 for 18:30 Registration and details: www. ise-tvrg.eventbrite.co.uk Secretary: Parminder Mann (email: parmindarkmann@ hotmail.com
Western Counties Tuesday 14 June Engineering Aid at the Cusp of History (Tuesday Group) Charles Pallant Pugsley Lecture Theatre, Queens Building, University of Bristol, Bristol BS8 1TH 18:00 for 18:30 Details: western.
[email protected]
Thursday 30 June Construction Products Regulation and CE marking updates Dr David Moore Arup, 63 St Thomas St, Avon, Bristol BS1 6JZ 18:00 for 18:30 Register at: http://bit.ly/ ISE_JUN_16
Friday 1 July BRE Innovation Park Watford (meeting point at M&S end of Cribbs Causeway Mall, Bristol; arrive by 07:45 latest) 08:00–16:30 Cost: £27.50 (travel, entrance, guided audio tour, and tea/coffee; lunch extra) Contact: Jeremy Crew Book by 23 May 2016 to secure place: www.istructe. org/events/regional/ western-counties/2016/ visit-to-bre-innovation-parkwatford Secretary: Mahara Booshanam (email: maharabooshanam@gmail. com)
Yorkshire Tuesday 14 June Stanbrook Abbey Speaker: TBA Thorpe Park Hotel, 1150 Century Way, Leeds LS15 8ZB 18:00 for 18:30 Details: j.f.carr@sheffi j.f.c arr@sheffield.ac.uk Secretary: Nick Buxton (email:
[email protected])
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Spotlight on Structures
June 2016
59
Spotlight on In this section we shine a spotlight on papers recently published in Structures – the Research Journal of The Institution of Structural Engineers. Structures is
a collaboration between the Institution and Elsevier, publishing internationally-leading research across the full breadth of structural engineering which will benefit from wide readership by academics and practitioners. Access to Structures is free to Institution members (excluding Student members) as one of their membership benefits, with access provided via the “My account” section of the Institution website. The journal is available online at: www.structuresjournal.org
Volume 6 Structures Volume 6 (May 2016) has recently been published online.
Editor’s highlights The Editor-in-Chief has selected the following highlights: Construction Details and Observed Earthquake Performance of Unreinforced Clay Brick Masonry Cavity-walls Marta Giaretton, Dmytro Dizhur, Francesca da Porto and Jason M. Ingham http://dx.doi.org/10.1016/j. istruc.2016.04.004 Finite element modeling of structural steel component failure at elevated temperatures Mina Seif, Joseph Main, Jonathan Weigand, Therese P. McAllister and William Luecke http://dx.doi.org/10.1016/j. istruc.2016.03.002
plates with damage under thermomechanical loading V.M. Sreehari and D.K. Maiti http://dx.doi.org/10.1016/j.istruc.2016.01.002 Robustness analysis of 3D Composite buildings with semi-rigid joints and floor slab S. Jeyarajan and J.Y. Richard Liew http://dx.doi.org/10.1016/j.istruc.2016.01.005 Analytical Modeling in Deformation Analysis of Interference-Fit Structures Nelli Aleksandrova http://dx.doi.org/10.1016/j.istruc.2016.01.003 Design implications of a new load introduction mechanism into concretefilled steel tubular columns Mohammad H. Mollazadeh and Yong C. Wang http://dx.doi.org/10.1016/j.istruc.2016.01.004
Influence of a Deformable Contour Ring on the Nonlinear Dynamic Response of Cable Nets Isabella Vassilopoulou and Charis J. Gantes http://dx.doi.org/10.1016/j. istruc.2016.02.007
Slots of Power-Law Profile as Acoustic Black Holes for Flexural Waves in Metallic and Composite Plates E.P. Bowyer and V. V.V. V. Krylov http://dx.doi.org/10.1016/j. istruc.2016.02.002
Full issue
Seismic performance of composite plate shear walls Sandip Dey and Anjan K. Bhowmick http://dx.doi.org/10.1016/j.istruc.2016.01.006
The issue also contains the following articles: Effect of the thickness of concrete cover on the fatigue bond strength of GFRP wrapped and non-wrapped reinforced concrete beams containing a lap splice Rayed Alyousef, Tim Topper and Adil AlMayah http://dx.doi.org/10.1016/j.istruc.2016.01.001 Buckling and post buckling characteristics of laminated composite
Hencky bar-chain model for buckling analysis of non-uniform columns E. Ruocco, H. Zhang and C.M. Wang http://dx.doi.org/10.1016/j.istruc.2016.02.003 Influence of soil–structure interaction on fragility assessment of building structures Chara Ch. Mitropoulou, Christos
Kostopanagiotis, Markos Kopanos, Dennis Ioakim and Nikos D. Lagaros http://dx.doi.org/10.1016/j.istruc.2016.02.005
Refined spatial beam-column element for second-order analysis of lattice shell structure Lin Qi and Yang Ding http://dx.doi.org/10.1016/j.istruc.2016.02.001 Second-order analysis of non-prismatic steel members by tapered beam–column elements Si-Wei Liu, Rui Bai and Siu-Lai Chan http://dx.doi.org/10.1016/j.istruc.2016.02.006 Review on recent developments in the performance-based performance-b ased seismic design of reinforced concrete structures Mohd. Zameeruddin and Keshav K. Sangle http://dx.doi.org/10.1016/j.istruc.2016.03.001 A general characterization of the Hardy Cross method as sequential and multiprocess multiproces s algorithms John Baugh and Shu Liu http://dx.doi.org/10.1016/j.istruc.2016.03.004 Impact Statement on “Partial Safety Factor for Reinforcement” Andrew Beeby and Paul Jackson http://dx.doi.org/10.1016/j. istruc.2016.02.004 Corrigendum to “Improved formulation of travelling fires and application to concrete and steel structures” [Structures 3 (2015) 250–260] Egle Rackauskaite and Guillermo Rein http://dx.doi.org/10.1016/j. istruc.2016.03.003
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And fin ally...
And finally... finally...
The place to test your knowledge and problem-solving ability. If you would like to submit a quiz or problem, contact
[email protected]
This month we bring you another question from the Institution’s Structural Behaviour Course. The topic is deflected shapes. Answers will be published in the July issue.
Question Choose the correct deflected shape under the load shown.
A
B
C
D
The Structural Behaviour Course is available at www.istructe.org/resources-centre/structural-behaviour and is free to Student Members of the Institution.
Answers to May’s quiz* Identify the correct bending moment diagram for the load case shown. Ignore self-weight. The bending moment should be drawn on the tension side.
A
B
C
Correct.
The right section – between the pin and the outer right support – has no external load on it and therefore cannot have moment. It rotates, but it does not bend.
The right section – between the pin and the outer right support – has no external load on it and therefore cannot have moment. It rotates, but it does not bend. Also, there cannot be moment on a pin joint.
* A production error meant that the wrong diagrams initially appeared in May’s quiz. A corrected version is available online.
D The point load pushes the pin down; therefore, the section between the middle support and the pin must go into hogging. You correctly identified that the portion on the right of the pin cannot bend.
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June 2016
Introducing the new bond Ancon has launched a new ultra-low thermal conductivity wall tie, based on the existing TeploTie product, with a conductivity of 00.7W/mK. This ultra-low thermal property virtually eliminates heat loss through thermal bridging in cavity wall constructions. The Teplo-BF basalt fibre wall tie features specially moulded safety ends that are said to improve buildability and enhance mortar bond strength, especially with lime and other slow-drying mortars. The composite material, created by setting pultruded basalt fibres in a resin matrix, provides the Teplo-BF with a combination of high strength and outstanding thermal efficiency. Available in the same range of lengths and types as TeploTie, the new wall tie is suitable for cavities up to 450mm wide and buildings up to 18m high. The ultra-low thermal conductivity means it is exempt from U-value calculations to BS EN ISO 6946, helping to minimise insulation and wall thickness, a particular benefit in modern low-energy construction applications. Further information: Ancon (web: www.ancon.co.uk)
Heating loss reduction boosted by airpop insulated floors With cavity wall and roof insulation now the accepted norm in new build properties, insulated flooring is gaining in popularity for new build houses and apartments. A new video (https://youtu.be/SU0kGYw8oB4) highlighting the advantages of airpop® floor insulation, available in simple slab or tailored ‘beam and block’ applications, has been launched. Installation of the expanded polystyrene system is simple and is said to result in reduced fuel bills and in time and cost savings during installation. Once in place, it provides a firm, level insulation ready to take the final screed. It can also create a ventilated airspace and even act as a stable ‘carrying board’ for underfloor heating systems below the screed. Further information: Airpop (web: www.eps.co.uk; email:
[email protected];
[email protected])
Revolutionary deburring machine ups capacity and turnaround at machine components manufacturer Engineering Utilities has supplied a revolutionary surface finishing machine to precision machined component manufacturer, CE Turner. The innovative Loewer deburring and edge finishing machine, sourced exclusively from Germany, has resulted in a much quicker turnaround in the deburring process at Leicestershire based CE Turner, which was previously conducted by hand. Installation of the new machine has freed up capacity and saved valuable man hours and associated costs. Nigel Soulsby, director at Engin eering Utilities, commented: “As the exclusive distributor of Loewer products, we recommend the Loewer DiscMaster 4TD-1500 Deburring & Edge Rounding machine to help increase performance, while reducing space and energy consumption.” Further information: Engineering Utilities (web: www.engineeringutilities.co www.engineeringutilities.com; m; tel: +44 (0)113 255 8887)
Soffi ts altern alt ernati ative ve steel system Ancon’s latest innovation, Nexus, developed in partnership with cut brick specialist Ibstock Kevington, offers a modular lightweight steel alternative to cast concrete brick-faced soffits. The Nexus system is designed to be easier to handle on site than precast concrete soffit systems and be used without the need for mechanical lifting equipment. To demonstrate the speed and simplicity of Nexus, an animated installation video is now available at www.ancon.co.uk/Nexus. This step-by-step video shows the process from initial fixing of the Ancon MDC Nexus support system, through the bolting on of the lightweight Nexus brick faced fa ced soffit unit and how it can be adjusted and levelled in all three planes, to the final pointing of the brick slip face. Further information: Ancon-Ibstock Nexus Nexus (web:ww w.ancon w.ancon.. co.uk/Nexus; tel: +44 (0)114 275 5224)
Working Workin g with Eurocodes? You’re Y ou’re not still doing it like lik e this, are you? To use Eurocodes you need to research and cross-reference them with various separate documents, document s, including: the National Annexe Annexes, s, Execution Standards and Non-Contradictory Complementary Information (NCCI). But not just once, you will need to reference forwards, backwards and forwards again, within, across and between documents. But there is another way - Eurocodes PLUS digitizes all 15,000 pages of the Eurocodes, making them more accessible and easier to understand, helping you reduce the time and cost of implementation. Find out how Eurocodes PLUS can help you clear your desk. Further information: information: BSI Group (web: www.bsigroup.com/eurocodesplus)
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TheStructuralEngineer June 2016
Timber design software: Teretron 2016+ The Rope Effect Ltd has released the first major update to its Teretron software. This new version contains a range of new features including: • multiple loading combinations for connections • fastener database • new glulam databases • a fully redesigned UI Connection design is supported extensively, with coverage of pinned and moment-resisting connections with all Eurocode 5-supported fasteners. Prices start at £245 per licence. Further information: The Rope Effect Ltd (email:
[email protected]; web: www.teretron.com)
Reveal hidden slab strength with LimitState:SLAB Limitstate:slab Limitstate :slab speeds up slab analysis and reduces the costs of building refurbishme refurbishment. nt. Determining the true strength of reinforced concrete slabs is crucial in many rehabilitation projects. The yield-line method excels at identifying slab strength, and LimitState:SLAB is the only software to systematically automate the method. It rapidly finds the critical failure mechanism for problems of any geometry. A Concrete Centre report on the subject states that yield-line design is “a great opportunity for more competitive structures” and engineers can benefit from it with LimitState:SLAB. LimitState:SLAB. Furtherinformation:Limitstate (email:
[email protected]; web: www.limitstate.com)
IDEA StatiCa: The future of steel connection design For many years, there was a huge gap in steel connection design, since all existing software packages were either not capable of handling complex connections that are often used in modern structures, or they were highly sophisticated FEM tools that are not productive enough to be used by practising engineers, and do not provide code checks. We are happy to announce that there is now a software package that fills this gap, by offering complete freedom in the geometry of the connection and full EC3/AISC checks. IDEA StatiCa is based on CBFEM, a new method that offers a much more detailed analysis of a connection and design “beyond the code”, since it uses finite element analysis to calculate the internal forces within a joint. This enables the engineer to model any connection even if it is not covered by current standards, such as EC3. At the same time, it offers some unique features like local buckling analysis and stiffness analysis/classification, which provide much more information for the behaviour of the connection. Further information: TechScience Ltd. (email:
[email protected];
[email protected]; web: www.idea-rs.uk; tel: 020 3579 9397)
Metsec provides framing solution to Manchester regeneration project voestalpine Metsec plc has been providing SFS infill walling for the construction of 29- and 21-storey new build apartment buildings, in the Cambridge Street regeneration project in Manchester. The construction of the two towers specified Metsec’s infill walling, which allows for a quick speed of installation. By utilising Revit (BIM) as well it allowed Metsec to produce drawings of the project, which allowed clashes to be detected and floor-by-floor material lists to be produced. One additional requirement on the project was working around the use of heavier brick-finish cladding, Corium, which was utilised by the architect, Terry Farrell, in ensuring the construction maintained characteristics synonymous with the area. Metsec was able to ensure the steel framing solution was as effi cient as possible when supporting the heavier cladding, which enabled a reduction in the cost of cladding brackets. Further information: Metsec (web: www.metsec.com; Metsec via @MetsecUK; facebook.com/MetsecUK) facebook.com/MetsecUK)
Bespoke posi-attic solution for Lincolnshire house UK supplier of trussed rafters, Pasquill, has created a bespoke posi-attic solution for an impressive 290m� five bedroom property in Washingborough, Lincolnshire. Pasquill converted an original design using traditional attic trusses into a version incorporating Posi-joists ™. Manufactured off-site by Pasquill, the posi-attic solution was then delivered to site fully ready to be craned into position, supported by design drawings detailing where each posi-attic truss was to be positioned. The traditional configuration of attic trusses sees solid structural timber members used. However, in the case of posi-attics the bottom chords are replaced with Posi-joists ™, i.e. a combination of the strength of a steel web with the light weight of timber flanges. The strength of a Posi-joist ™ floor provides increased living space within an attic, thereby delivering maximum value to the homeowner. Furtherinformation:Pasquill (web: www.pasquill.co www.pasquill.co.uk) .uk)
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ANALYSIS & DESIGN
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RETIREMENT SALE Owner of well established protable specialist timber frame structural engineering consultancy is looking to retire, either completely or with reduced hours to help the transition to a new owner. Current turnover is in excess of 200k p.a.. The main o ce is situated in the West Midlands but varied client base could be easily transferred to a new owner as very few are local. Current owner has 40 years experience and contacts within the industry. The business oers an excellent opportunity for an existing consultancy to acquire new business with little additional overhead or advertising. Equally the business would be of interest to individual qualied engineers looking to start on their own with a ready made client base and business infrastructure. 90% of the turnover is recurrent work from existing clients, leaving room for a buyer to expand the business through re-invigorated marketing. Interested parties please email
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DEPARTMENTAL HEADS SOUTH LONDON OFFICE
Our client, a well-known and reputable multi-disciplined Practice wishes to appoint two new Directors with specific experience and knowledge in the specialised fields as below. STRUCTURAL Engineering Lead - Ref. 6305 To lead the structures team comprising a small team of principal, senior and To intermediary engineers producing design work for established end users or as partners with recognised major contractors operating throughout the UK. The business unit has a broad range of client relationship relationships s serving the commercial, educational, health and leisure sectors and the Board has set a strategy to expand the Unit’s Unit’s presence and increase market share. The right individual will therefore possess sound managerial and business planning skills and the confidence to take the business forward through having excellent leadership and organisational ability. AVIATION Lead Lead - Ref. 6317 6317 Long established in this specialised field, the new Director for the Aviation division will join the business at a time of positive change when the Board has determined that the Aviation business can and should win and execute more tier one work given the fine reputation it has enjoyed over many years with airport owners and airport operators throughout the UK and in several overseas venues as well. This individual must have a solid backgroun background d in the planning, design and construction of civilian and military airports. Well connected within the Airport community the individual will have the business development, commercial and technical knowledge associated with Airport developments from grass roots to completion and be attracted by this opportunity to oversee a programme of profitable expansion and receive the recognition for achieving this objective through financial and promotional incentives. The packages relating to both these appointments are highly attractive, details to be discussed at interview. For both above roles our client is prepared to consider candidates who might not have reached this level of seniority just yet but believe they have the potential and want the chance to prove it.
Please apply in confidence quoting ref to David Knowles (david.knowles@
[email protected]) ecutivesear ch.co.uk) tel 01767 631843 for a preliminary discussion if required.
Structures ResearchJournalofTheInstitutionof StructuralEngineers
Papers are accepted from, but not limited to, the following subject areas: materials structural form ● structural design ● construction engineering ● structural innovation ● extreme events ● sustainability ● architectural topics (that impact structural performance) ●
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NOW AVAILABLE www.structuresjournal.org
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Editor-in-Chief: Professor Leroy Gardner (Imperial College London) Editor-in-Chief: ● All articles articles freely freely available available to fee-payin fee-paying g IStructE IStructE members via www.istructe www.istructe.org/my.org/my-account account ● Student Members should contact their university library for access details ●
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further your career Team Leader
Senior Engineer / Associate
Associate Structural Engineer
Manchester £60,000-£65,000 Plus Benefits
Bristol £55,000-£60,000 Plus Benefits
Central London £75,000-£80,000 Plus Benefits
Our client is currently looking for a dynamic candidate to help lead and develop their structural engineering business whilst managing numerous exciting projects. You will be expected to build and promote the company externally, networking with existing and potential clients. For this role our client is looking for a candidate with experience in building structures which has been gained across a broad field, proven structural design and project management experience, with good leadership and business development capabilities.
This practice and its staff have a wealth of experience in the design of buildings intended for public use including housing, industrial and retail warehouses, supermarkets, petrol filling stations, offices, commercial and retail developments, as well as Listed Building alterations involving submissions to the Fine Arts Council for the structural schemes. The growth of the practice is based on its innovative approach to design and the ability to work within budget and program constraints. As a result of their success they need an engineer to take a senior role within the practice, who will enjoy working closely with architects on exciting buildings projects.
This leading consultancy offers a multi-discipline service from its Central London office. office. They are currently seeking an associate structural engineer to take a lead role on projects up to multi million pounds in value, managing more junior engineers and technicians. The office enjoys a friendly atmosphere, where the teams are client focused and success driven. A Chartered engineer with excellent building structures design skills.
Senior Structural Engineer Central London £47,000-£52,000 Plus Benefits This medium sized award-winning practice is seeking an ambitious and self motivated engineer at senior level to join their thriving business. business. Working closely with with architects and more junior designers, you will oversee buildings structures projects ranging from a £50,000 domestic extension to £100million commercial scheme. The role offers autonomy autonomy and a superb opportunity for a senior engineer looking to progress progress their career. The ideal candidate will be Chartered or near to with excellent technical design and communication skills.
Associate Director Leeds £58,000-£62,000 Plus Benefits This is a key position with a prestige consultancy. You will have responsibility for initial scheme design, fee negotiations and will manage project teams during detail design phase. They require a talented structural engineer who has good commercial and client liaison skills. You will have the opportunity to work on a challenging stream of high profile projects and the opportunity to quickly progress to Director level.
Senior Structural Engineer Dorchester £40,000-£45,000 Plus Benefits Our client's small but busy office has a continued workload developed through their excellent reputation. They are currently seeking a professional engineer to maintain current workloads & develop new relationships. The opportunity to develop into a management position is on offer for the right person.
Partnership Opportunity
Associate Director Norwich £60,000-£65,000 Plus Benefits This busy, friendly but progressive Structural Engineering Consultancy now require a top level individual to help manage projects projects and people. people. Current projects are up to the value of £50 million and include a warehouse conversion, prestigious housing developments and a variety of new build commercial projects. You will be responsible from the initial design through to overall completion of schemes. Supervising a small small team of technicians, you will also liaise directly with clients and be a flexible team member.
Central London £110,000 Plus benefits An opportunity for a driven engineer to join the structures teams of this blue chip company in Central London. Their reputation for delivering innovative and sustainable designs is globally recognised and sought by clients across all sectors. You will become become involved in leading prestigious and exciting national and international schemes, whilst successfully carrying out a business development and client liaison role. role. An inspirational leader with a broad experience in the buildings structures market. The role offers a partnership opportunity for the right candidate.
Find more jobs online at conradconsulting.co.uk For more information about any of these positions, please contact
[email protected] or, for a confidential chat, call Graham on 0203 1595 387
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This is a unique opportunity for an ambitious Chartered Structural Engineer to run, manage and own a regional consultancy as an independent extension of an established practice.
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Consulting Civil and Structural Engineers
Ross-Gower Associates
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Chartered Structural Engineer, Director Designate We require a Chartered Engineer (MIStructE preferred) with a mbition to become a Director of a longstanding practice of Consulting Civil and Structural Engineers. A key part of the role will include structural certification/checking under the Institute’s SER Scheme and the Engineer must therefore have at least 5 years post-chartership experience in all forms of domestic (new build and renovation) and commercial construction, typically up to 6 storeys in height. Founded in 1981, we are a progressive, award winning practice, with an upcoming workload of high profile projects. We presently have 10 technical staff including 3 chartered engineers/directors, one of whom is retiring later this year. Experience of taking a lead role in the management of medium and large scale schemes is expected. A full local housing licence is available, and the position would suit a person seeking a change in lifestyle for themselves and/or their family. Assistance with relocation will be provided to the successful candidate.
Structural Engineer – Building Control Hay 10 – £34,380 - £40,896 We need a professional structural engineer – who wants an opportunity to be involved in more complex and exciting projects – to support the regeneration and development of our vibrant and diverse borough. Become part of an experienced and supportive team and we will offer you development opportunities opportunities and training. You’ll have considerable building control experience covering major commercial and residential projects through to domestic properties. Keen to make a difference, you’ll bring a comprehensive understanding understanding of the current building control system and relevant legislation. A confident communicator, you’ll also represent the Council in building-related matters. Above all, your ability to get to grips with the sheer breadth of projects in Southwark will make you stand out. To find out more visit www.jobsatsouthwark.co.uk Closing date: 15th June 2016. Interview/Assessment: 24th June 2016.
Please apply initially by email to
[email protected] with a CV and covering note.
[email protected] with
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Senior Structural Engineer Central London Ref: 51003 Up to £50,000 + Benefits Premier 50-strong niche consultancy based in Central London has a requirement for a Senior Structural Engineer up to Associate level to join the the expanding expanding studio as it continu continues es to win new work including a £60million project with (arguably) the best Architects in the world. Candidates will need to be Chartered with IStructE and/or ICE and must have worked in either premier or niche London consultancy.
knowledge based recruitment in structural engineering consultancy Structural Design/ Project Engineer South West London Ref: 50912 Up to £40,000 + Benefits
Premier niche consultancy has a requirement EXPEDITION for a Structural Design/Project Design/Project Engineer to join the head head of�ce. Candidates Candidates will will need to be a Graduate member of IStructE and/or ICE, have Civil Infrastructure a MEng/MSc and will have, as a minimum, Engineers good design skills in the major materials. They should be capable of working Central & Greater London with support and looking to Up to £55,000 + Benefits advance their career with one of Walker Dendle Technical has around 20 roles London’s top consultancies. for Civil Infrastructure Engineers across Greater London from Design Engineer up to Associate grade. Candidates will need to be a Graduate or Chartered member of ICE, be educated to MEng/MSc level and have as a minimum, good design skills in roads, drainage & associated infrastructure works and at more senior level good project-running skills.
HEYNE TILLETT STEEL
Senior Structural Engineer Central London London Ref: 51007 Up to £52,500 + Benefits FLUID STRUCTURES
Leading premier international consultancy with a London studio has a requirement for a Senior Structural Engineer to join the business due to a continuing increase in workload. Candidates will need to be near or recently Chartered with IStructE and must have gained experience working on large newbuild high-rise RC and steelwork construction at another premier London-based consultancy.
Chartered Structural Engineer Central London London Ref: 50933 Up to £53,000 + Benefits MILK STRUCTURES
Premier consultancy based at London Bridge has a requirement for a Chartered (or near) Structural Engineer to join one of its teams to work on a new large high-rise residential development. 2 Associate Candidates will need to be Chartered with Structural Engineers IStructE and/or ICE and must have good (current) design and project-running Central London Ref: 50909 experience gained working at Up to £65,000 + Benefits another premier consultancy on Rapidly-expanding premier consultancy large new-build projects based in Farringdon has a requirement for 2 Associate-lev Associ ate-level el Structural Structural Engine Engineers ers to manag manage e and develop existing teams as well as continuing to run projects. Candidates will need to be Chartered with IStructE (ideally) and/or ICE and have good project and teamrunning skills gained working at another premier or niche structural engineering consultancy. PRICE & MYERS
2 Structural Project Engineers North London London Ref: 51001 51001 Up to £47,500 + Benefits Rapidly-expanding niche Structural Engineers based in North London has a requirement for 2 Structural Project Engineers to join the practice as it continues to win exciting new projects. Candidates will need to be a Graduate member of IStructE and/or ICE, be educated to MEng/MSc level and will have gained good design and project-running skills on typical niche consultancy innerLondon projects.
ECKERSLEY O’CALLAGHA O’CALLAGHAN N
STRUCTURAL AWARDS
WANTED!
For the sixth year running we are a proud sponsor of The Structural Awards by IStructE and this year we have again chosen to sponsor the “Award for Community and Residential Structures”. Structures”. Good luck to all consultancies consultancie s that have entered and we are keen to continue to offer our ongoing support to the industry through this sponsorship.
With the London market now totally candidate-driven we seek good sole-agency candidates looking for a move in premier or niche London consultancy. We will be able ENGENUITI to secure you a number of interviews with some of the best London consultancies of differing sizes, that have an architectur architectural al edge, paying the best salaries & benefits and providing a dynamic studio environment working on a range of interesting and challenging projects. IMAGES SHOW RECENT PROJECTS
UNDERTAKEN UNDERTA KEN BY SOME OF OUR CORE CLIENTS
CONISBEE
T 020 8408 9971 E
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