39CONNÆCT

services without restricting head height andthe residential floors were typically flat platedue to the head height constraint – 2.7 mceilings. These slab systems were chosenwith the aim of providing the most efficientand low-cost solution to the client. This wasachieved by the attendant reduction inmaterials and increase in the speed ofconstruction without compromising thestructural integrity, quality or architecturalrequirements of the structure.The Level 1 podium slab is a heavy transferslab with complex concrete profiles due tothe combination of varying slab thicknesses,deep folds and steps, large spanning beams –some in excess of 16 m – to cater for thelarge column-free space below required forthe loading dock, diagonal beams and themagnitude and positioning of the transfercolumns. Input from the design team wascritical to arriving at a practical solution. Theslab depths and beam dimensions werereviewed – in discussion with the consultingengineers, the architect and services con-sultants – and this led to significant changes inthe concrete profiles. Due to the geometricconfinements of some slabs and beams, weused 12.7 mm and 15.2 mm diameter strand.

In addition, the dimensions of various transferbeams were restricted in depth and widthand could not be increased due to headheight limitations – widths could only beincreased to a certain extent. This createdissues with practicality and great difficulties inphysically installing the considerable quantityof post-tensioning strand required to controldeflections. Therefore, the design of thebeams used a combination of BBR CONAflat slab post-tensioning and BBR VT CONACMI which reduced congestion and improvedthe construction efficiency of the floor.With the use of post-tensioning, thoughtfuldesign and efficient construction, the projectrecovered from being well behind its targetconstruction program – when we began thesuspended structure – to finishing ahead ofschedule on its completion. l

MAGISTRATES’ COURTS, ESSEX,ENGLAND

Reducing legal costs

Post-tensioning which was designed andinstalled by BBR Network MemberStructural Systems UK has beenused to reduce the environmentalimpact on two new Magistrates’ Courtbuildings currently being developed inColchester and Chelmsford, Essex.Richard Gaskill takes up the story.Both buildings were designed to sit onexisting car parks and have a similarlayout. During the initial design reviewworkshops, some 50 potential designchanges were identified with 11 ideasflagged up for further discussion and,finally, this number was distilled down tofour which were analyzed in detail. Post-tensioning, along with retention ofexcavated material, pre-engineered stairsand CFA replacement piles reduced theoverall cost of the structures. TheColchester structure had slab depthsvarying from 200 mm to 400 mm,whereas the one in Chelmsford variedfrom 200 mm to 500 mm thick. TheMagistrates’ Court scheme was procuredthrough a Private Finance Initiative (PFI)scheme by the County Council, to securethe new courts as part of a countywidecourt strategy. Her Majesty’s CourtService is expected to pay £30 millionfor the Colchester Magistrates’ CourtComplex. The Court is due to hold itsfirst case in summer 2012.The Courthouse is designed to theHMCS Design Guide 2007 and is set toachieve BREEAM excellent and otherspecific targets from the UK GovernmentFramework for Sustainable Development.

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TEAM & TECHNOLOGYOWNER Her Majesty’s Court Service

MAIN CONTRACTOR Galliford Try

TECHNOLOGY BBR CONA flat

BBR NETWORK MEMBERStructural Systems (UK) Ltd

Local insight: Dee Why

Today, Dee Why is undergoingconsiderable urban regeneration

and proving popular with youngprofessionals, perhaps attracted by aneasy commute into the Sydney CBD. The first written reference to the townappears in the field book of Irish-Australian explorer and surveyorJames Meehan: “Wednesday, 27th

Sept, 1815 Dy Beach – Marked aHoney Suckle Tree near the Beach.”Explanations for his description rangefrom the DY simply being a code thathe used on maps, or that it originallycame from the local Aboriginallanguage or was derived fromcalculus and refers to the shape of thecurve of the beach as seen on a map.From 1940, the town was known as‘Deewhy’ and it was only in the 1950sthat it took the present form – DeeWhy.Since construction of the new civiccentre in the early 1970s, the townhas housed the administrativeheadquarters of Warringah Council,the local authority.

TEAM & TECHNOLOGYOWNER Dee Why Developments

MAIN CONTRACTOR Thiess Pty Ltd

DESIGNER Structural Systems Limited (Australia)

TECHNOLOGY BBR CONA flat BBR VT CONA CMI internal

BBR NETWORK MEMBERStructural Systems Limited (Australia)

… A COMBINATION OF BBRCONA FLAT SLAB POST-TENSIONING AND BBR VTCONA CMI ... REDUCEDCONGESTION AND IMPROVEDTHE CONSTRUCTIONEFFICIENCY OF THE FLOOR.

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44 CONNÆCT

ExCeL London is an international events andconference centre, located in the RoyalDocks, which hosts a variety of events fromhigh profile exhibitions and conferences tointernational association meetings, awardceremonies and sporting events. In 2012, thevenue will host seven Olympic and fiveParalympic events.This second phase of development was afurther massive investment focused onproviding superior world class event facilitiesin London, as well giving added support tothe capital’s ambition to host an everincreasing number of high profile domesticand international shows. This internationalevents venue – now valued at around £300million in total – is the largest and mostversatile space in London.

In addition to the vast halls totaling 65,000 m2, there are five on-site hotelscatering for budget and luxury clients, whichprovide 1,500 rooms, plus over 90 fullyserviced apartments, 45 meeting rooms and3,700 on-site parking spaces.We teamed up with concrete constructionspecialist P.C. Harrington Contractors, whohad commenced a 47-week contract whichincluded the groundworks, drainage, pile capsand structural concrete for construction ofthe new North Hall and lorry way, as well asthe South Hall, lorry way and ramp.The scheme was designed by maincontractor Sir Robert McAlpine’s in housedesign team who indicated a PT density of30 kg/m3 for North and South Lorry waysand 25 kg/m3 for both the North and South

Hall. As part of their specification, they hadindicated that all strands should be 15.7 mmseven wire super-grade with a minimumbreaking load of 279 kN.Concrete strength was specified as aminimum of 40 MPa and the designaccommodated a one hour fire ratingrequirement. Each hall was separated intopours – with the North Hall having 10 andthe South Hall 12. The lorry ways were splitinto a further three and four poursrespectively. The slab was nominally 240 mm thick, with 475 mm deep beams – which covered approximately 65% of thescheme – at centers ranging from 7.8 m to10.5 m and a 600 mm deep beam at oneend. Pours 3, 6, 9 and 12 were 270 mm thick on the North Hall and 300 mm thick on the South Hall, with all ofthese areas being adjacent to the lorryways. The area of the halls and lorry waystogether totaled 27,689 m2.During our 16 weeks on site, we installedour CONA flat 206, 306 and 406 bondedpost-tensioning systems. Internal pans, where

International showcaseEXCEL, LONDON, UK

ExCeL London represents a £150 million investment in theexhibitions industry. The recent second phase of development haspushed ExCel London to around 100,000 m2 of flexible flat floor

exhibition and conference space. Richard Gaskill of Structural Systems– the BBR Network Member in the UK – describes this huge development.

TEAM & TECHNOLOGYOWNER ExCeL London

MAIN CONTRACTOR Sir Robert McAlpine

TECHNOLOGY BBR CONA flat

BBR NETWORK MEMBERStructural Systems (UK) Ltd

45CONNÆCT

required, were installed along each side adjacent to the lorry way toallow post-tensioning to take place.The project has provided much-needed additional exhibition andconference space, as well as a 5,000 seat semi-permanent auditoriumat this venue. One of the more unusual features of the constructionprocess was that – after completion of the column pile caps – themain contractor erected the steel frame and roof, while thesuspended post-tensioned floor slabs for the exhibition halls andlorry access way were constructed afterwards. Among the challengesduring our construction period was the need to maintain access formaritime exhibits during the London International Boat Show! l

Bahrain Investment Wharf (BIW) is a joint venturebetween the Bahrain Government and Al Khaleej

Development Company (Tameer). Roland Zachar, DesignManager for BBR Network Member NASA StructuralSystems LLC, reports how they have helped to developthe wharf by post-tensioning the floor slabs of the newfive star BIW Hotel. The master plan of the US$2 billion BIW project is divided intofour major sectors – an industrial park, business park, residentialand service areas – totaling 1.25 million square meters ofrentable area. BIW is strategically located – near to Bahrain’sInternational Airport, the Seaport, the highway leading to thecauseway linking Bahrain and Saudi Arabia, as well as the newlyproposed causeway between Bahrain and Qatar – for ease ofimport and export of goods.Given the significant overall length of the project, each level of thehotel was divided into three pours by the inclusion of expansionjoints. All 13 levels above the ground were designed as post-tensioned flat slabs using the BBR CONA flat system with 305 and505 anchorage sizes. The lower, more heavily loaded levels,consisted of 220 mm deep post-tensioned flat slabs, whereas slabdepths of only 200 mm were required for the upper levels.The majority of projects in the Middle East over recent years havebeen carried out at a much faster pace than is typically experiencedin Europe. The period between signing the contract, finalizing thedesign, mobilizing on site and pouring the concrete can be limited toa matter of days – and this BIW job was a prime example. A pricewas agreed with the main contractor on Thursday, the letter ofintent received on the following Saturday – and the first pour atground floor level was cast within a 10 day period.The whole project progressed at a similar pace – with all 21,000 m2 of post-tensioned slabs designed, installed, poured andstressed in less than five months from receiving the go-ahead onthe project. In recognition of our excellent service during theworks, the contractor awarded us the design and installation ofpost-tensioned slab for the associated multi-functional hall. l

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BIW HOTEL, BAHRAIN, UNITED ARAB EMIRATES

Fast and five star

TEAM & TECHNOLOGYOWNER Bahrain Investment Wharf

MAIN CONTRACTOR Al Namal Construction Co.

TECHNOLOGY BBR CONA flat

BBR NETWORK MEMBERNASA Structural Systems LLC (United Arab Emirates)

Local insight: Docklands

The ExCeL exhibition centre sits close to the Isle ofDogs, in the heart of an area defined by its seafaring

and trading past. Although hard to imagine now, LondonDocklands was once a hive of activity, fuelled by thearrival and departure of ships transporting goods fromall over the world. The docks here grew up primarily inthe early 1800s, with later additions in 1880 and 1921.However, by the 1970s, commercial shipping consistedmainly of container ships which required deep waterberths. Thus, the old docks progressively fell into disuseuntil the vision of regeneration was born in the 1980s.Now, the shining Canary Wharf development – duringwhich Britain’s tallest building was constructed – standsas a beacon for regeneration and has established asecond major financial centre in London.

THE SLAB WAS NOMINALLY 240 MM THICK, WITH 475 MM DEEPBEAMS – WHICH COVEREDAPPROXIMATELY 65% OF THE SCHEME...

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46 CONNÆCT

MAKING WAVESThe £19 million new Marine Building atPlymouth University now accommodatesstate-of-the-art research facilities,including the most technically advancedwave tank and testing facilities in Europe.The two giant ocean and coastal wavetanks are – at 48 m by 16 m – nearlythe size of an Olympic swimming pool,and will contain 225,000 liters of water,all suspended from the floor above.During the project, BBR NetworkMember, Structural Systems UK provid-ed post-tensioning expertise for the con-struction of some of the largest concretebeams ever produced in the UK.The structural system chosen wasprecast post-tensioned beams spanning16 m, with secondary spanning 100 mmdeep wide-slab precast unitsincorporating a 125 mm structuralscreed. The 32 beams are 500 mm by750 mm deep at midspan, reducing to400 mm by 690 mm deep at 3.4 m from

1 each column to accommodate a cranefixed to the underside of the beams.Each beam comprised two BBR VTCONA CMI 706 bonded multistrandanchors with single end stressing. Asdeflection remained an issue after initialstressing, a full-scale FE vibration analysisconfirmed a response factor of 3, thiswas accepted by the building client.Transporting the 16.3 m beams to sitewas a logistical feat in itself and requireda specialized trailer and a special highload capacity crane, imported from Asia,on site to lift the beams into position.Beam design also had to consider thedifferent permutations and stressesinvolved in the lifting process. Supporting the beams on a relativelysmall column width meant that thetraditional recess provided for the multi-strand anchor interfered with theanchorage length for the supportreinforcement. Placing the anchorbearing plate on the external face of the

UNIVERSITY BUILDINGS IN THE UK AND AUSTRALIA

Degrees of differenceTwo different university buildings, two different countries –

and two very different challenges. Long after they hadgraduated, engineers from the BBR Network recently found

themselves back on the campus. In both cases, they providedtechnically excellent solutions in some very unusualcircumstances – each one leading edge and perhaps providingfood-for-thought for any engineering undergraduates whohappened to pass by the construction sites!

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47CONNÆCT

beam removed the recess requirement, butleft the anchor exposed. The architectaccepted the detail once a plastic end capwas sourced to minimize the impact of theprotrusion on the building space. We also undertook the in-situ prestressing oftwo 800 mm wide by 1,000 mm deep beamsproviding support for one of the suspendedcoastal tanks. Use of two CONA CMI 706tendons for each beam eliminated threelayers of congested bottom reinforcementand provided a crack-free structure, increasingthe durability and design life of the tank.

VITAL DEGREESMichael Losinski, Design Manager forAustralian BBR Network Member, StructuralSystems Ltd, reports on the engineeringchallenges and development of theconstruction techniques that led to thesuccessful completion of SwinburneUniversity’s iconic Advanced TechnologyCentre in Melbourne.We provided the main contractor with acomplete structure package that includedpost-tensioning design and installation,formwork, steel fixing and concreteplacement. Understandably, SwinburneUniversity was keen to make use of their newfacility and all parties were constrained by anextremely tight design and constructionprogram. The horizontal structure

2

incorporated approximately 120 t of 15.2 mmdiameter slab and beam post-tensioning,stressed to 212 KN per strand. In addition tothis, seven strand vertical multistrand PTtendons were also installed at the extremecorners of each of the service cores tocounteract the large lateral loads generatedwithin the buildings.The large double-height clear span lecturetheater, presented our design team with aseries of unique challenges. To achieve thelarge open space, four complex transferbeams were required at level 3. These were

formed with a maximum structural depth of3.45 m and each was required to spanapproximately 20 m to carry all eight of thelevels above. The BBR VT CONA CMImultistrand system was utilized within thesebeams, with each beam containing a total of93 strands each – or three 31 strand tendons. Stage stressing of both monostrand andmultistrand tendons within the transfer deck was imperative to ensure adequate stress anddeflection criteria were met throughout all construction stages. Monitoring of beamedges was conducted by daily surveys toensure that shrinkage of the transfer beamswas maintained within the calculated limits.Construction requirements and site logisticsrequired that the large transfer beams werepoured as one single element with no

horizontal construction joints. This ultimatelyraised concerns regarding the heat ofhydration generated within the deep beams.Of major concern were the excessivedifferential temperatures that could occurthrough the large depth, potentially generatingstructural voids and failure planes within thebeams. To combat this issue, specific concretedesign mix, formwork and curing procedureswere implemented to monitor and minimizethe calculated temperatures expected. Along with our concrete suppliers, weundertook extensive analysis of the concretemix, and thermocouplers were installed withinall the transfer beams to monitor the heatgenerated. The delivery temperature of theconcrete was imperative in achievingacceptable temperature criteria and, hence,we explored – and later used – cooledaggregates. This additional measure ensuredthat the maximum delivered concretetemperature did not exceed 10 ºC.The formwork remained in place, acting as aninsulator until ambient temperatures in thebeams had been achieved. Curing of the slabsurface was vital to ensuring that surfacetemperatures were kept at a relatively consis-tent rate, compared to that within the beams. Results from the thermocouplers indicatedthe maximum core concrete temperature wasapproximately 52 ºC and the differential tem-perature between core of beam and externalface was minimized to less than 20 ºC. The use of multiple post-tensioned systems,techniques and design considerationsthroughout this structure, ensured thatconstruction continuity could be maintained.Casting transfer beams in one single pourmeant that formwork could be stripped at anearly stage allowing for all contractors tobegin works earlier, thus meeting the tightdeadlines set by the client. l

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TEAM & TECHNOLOGIES

PLYMOUTH UNIVERSITYOWNER University of Plymouth

MAIN CONTRACTOR Leadbitter Group

TECHNOLOGY BBR VT CONA CMI internal

BBR NETWORK MEMBERStructural Systems (UK) Ltd

SWINBURNE UNIVERSITYOWNER Swinburne University of Technology

MAIN CONTRACTOR Kane Constructions

ARCHITECT H20 Architects

STRUCTURAL CONSULTANT Watermans

PT DESIGNER Structural Systems Limited

TECHNOLOGY BBR CONA flat BBR VT CONA CMI internal

BBR NETWORK MEMBERStructural Systems Limited (Australia)

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DURING THE PROJECT, BBRNETWORK MEMBER,STRUCTURAL SYSTEMS UKPROVIDED POST-TENSIONINGEXPERTISE FOR THECONSTRUCTION OF SOME OFTHE LARGEST CONCRETE BEAMSEVER PRODUCED IN THE UK

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51CONNÆCT

TANKING UP IN SPAINOver the past seven years, BBR PTE has constructed four LNG tanksin Barcelona and one in Cartagena as part of Enagas installations andare now constructing a further two tanks for them in Gijon (seepages 52 & 53).

AWARD-WINNING LNG CONSTRUCTIONThe UK’s largest civils project in 2008 was declared the winner in thecivil engineering category of the Concrete Society Awards. The teamfrom BBR Network Member Structural Systems (UK) constructedfive 92 m diameter post-tensioned LNG storage tanks at the SouthHook site in Pembroke Dock in South Wales.

TANKS

& SILOS

WORLD’S FIRST OFFSHORE LNG TERMINALThe Isola di Porto Levante offshore LNG Terminal – a Floating Storage and Regasification Unit – is a gravity-based structure (GBS) and wasconstructed in a large dry dock facility in southern Spain.The project attracted a special mention in the 2010 fib Awards for Outstanding Concrete Structures and the judges praised the project for theway in which congested areas were handled and for the high quality of workmanship.BBR PTE developed the post-tensioning works in association with two other companies. The GBS was taken by tugboat to its final destination –17 km off the coast of Italy.

78 CONNÆCT

The Al-Wehdah Dam is a roller-compactedconcrete (RCC) dam, designed forconstruction in two stages. The first stagetakes it to 70 m high to a crest elevation of116 m, and the second stage involves raisingit by 30 m to a crest elevation ofapproximately 146 m. The owner required that provisions should beincluded to permit the raising of the dam at alater stage. The dam was constructed usinggrout-enriched RCC (GERCC) facing on boththe upstream and downstream surfaces.A grout curtain cut-off was constructed at theupstream foot of the dam and the abutmentswere extended to a depth sufficient toaccommodate second stage construction. The multi-stage intake structure consisting of a

tower with three intakes at heights of 70 m,80 m and 90 m – along with two concrete-encased 3 m diameter steel conduits and adischarge structure – was constructed in theleft abutment.Our scope, as nominated subcontractor,consisted of the construction of all the CVC

(Conventional Vibrated Concrete), in additionto all necessary upstream and downstreamfacing formwork using climbing formwork atthe upstream face and stepped formwork atthe downstream face and for galleryconstruction.The very tight schedule for constructiondemanded the use of special climbingformwork and scaffolding – plus a 24-hourworking pattern, as the RCC work wascarried out in a continuous 24 houroperation. In just 72 hours, we had completedthe formwork for the grouting gallery –approximately 1,170 liner meters of threemeter high galleries of widths varying from 1.5m to 2.4 m. The PT bar technology helped usgain time and enough strength to deal withthe great forces projected from the RCC andthe working plant. l

TEAM & TECHNOLOGYOWNER The Ministry of Water and Irrigation,Jordan Valley Authority

MAIN CONTRACTOR Ozaltin ConstructionTrade & Industry Co.

DESIGNER Montgomery Watson Harza (MWH)

CONCRETE WORKS Marwan Alkurdi &Partners Co. Ltd. (Nominated Subcontractor)

TECHNOLOGY PT bar; climbing formwork

BBR NETWORK MEMBER Marwan Alkurdi &Partners Co. Ltd (Jordan)

UK-based BBR Network Member, Structural Systems hasbeen busy assisting with preparations for the 2011 HydePark’s Dextro Energy Triathlon ITU World Championship byconstructing a temporary structure which forms the TataSteel VIP zone. The pavilion is constructed from ‘post-tensioned steel technology’which is an innovative solution and believed to be the first of its kindto be applied to such a temporary structure in the UK.Structural Systems has been working in collaboration with S2 – anAustralian company wihich specializes in the design and constructionof large span steel solutions. The structure comprises a post-tensioned structural steelwork hollow section latticed arch that ispinned at each corner. l

TEAM & TECHNOLOGYOWNER TATA Steel

MAIN CONTRACTOR TATA Steel

DESIGNER S-Squared Corporation Pty Ltd

TECHNOLOGY BBR VT CONA CMI external

BBR NETWORK MEMBER Structural Systems (UK) Ltd

TRIATHLON VIP ZONE, LONDON, UK

First for temporary PT structure

BBR Network Member, Marwan Alkurdi & Partners has been working on atechnically demanding construction project for the new Al-Wehdah Dam.The site is in the northern part of the Hashemite Kingdom of Jordan on the

Yarmouk River which forms the border between Jordan and Syria in this location.

AL-WEHDAH DAM, IRBID, JORDAN

Strength against forces