Crystalamazes assustainableurbanshowcase

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naturally ventilated in both theoffice and exhibition crystals,using opening vents in the facadesand roofs.

The dynamic building form isdriven by this sustainable agendaand incorporates two parallelo-gram “crystal” forms broken into aseries of triangulated facets andlinked by an internal street.Because the facets have varyingorientations, they will reflect thelight differently to create, accord-ing to the architect, a dynamic andreciprocal reflection of its water-side setting.

Each of the two crystal-shapedsections is supported by 14 taper-ing steel columns. The north sidehouses an exhibition space explor-ing best practice in urban planningand design. To the south are officesfor 250 Siemens staff plus confer-ence facilities including meetingrooms, a café, a restaurant and a300-seat auditorium.

At either end of the triangularstreet are public and privateentrances, the public one to theeast nearest the dock. In the cen-tre of the street is the main recep-tion with views into the exhibitionhall.

“No piece of glass or angle ofsteelwork is the same, which is a

very interesting challenge,” saysSebastien Ricard, a director ofWilkinson Eyre.

“While the facade appears to bemade up of a set of random shapes,we created a rational geometry bydefining the overall building formaround two main parallelogramsin plan with a very large spanstructure inside.

“Working with Arup, wedesigned a diagonal grid, a set ofvariable span portal frames. Thecolumns/roof beams vary inheight/depth and thickness in rela-tion to their respective span in aparametric way, offering an opti-mised lightweight structure which‘picks up’ all the key nodes defin-ing the roof geometry.”

The lightweight facade struc-ture of the exhibition section isself-supported from the roof to the

The mostinteresting andelegant part of thestructural design isthat of the taperingand twistingcolumns, accordingto structuralengineer ChrisCarroll, director ofArup.

The columns — 14 per crystal — arelocated in the pointswhere the roofplane folds in orderto maximise thecolumn-free spaces,and range in heightfrom 8-17m aboveslab level.

These areconnected by roofgirders to make aportal frame withspans rangingbetween thecolumns from 9m tothe maximum spanof 42m. However,they also act ascantilevers.

WIND LOADSTo provide sufficientwind load rigidity,the columns rotatethrough 90 degreesand taper towardsthe ground. Bytransforming insection over itsheight in this way, itis strong in onedirection at the top(in the direction ofthe portals) andstrong in the otherdirection at thebottom (to allow thecolumns to canti-lever from the basein this direction).

All have “collars”for the floor to slotneatly beneath.

“Our aim was todeliver somethingstructurally elegantthat minimised theamount of material

and optimised cons-truction time byprefabricating andmodularising asmuch as possible,given that thegeometry hadinherentcomplexity,” saysCarroll. “Thestructure wasreacting to thedesign rather thandriving it.”

RAINWATERCOLLECTIONFour of the cornernode columns —two per crystal —have integralstainless-steeldrainpipes thatunobtrusivelydeliver water intothe rainwatercollection systemand are cranked tofollow the facade.This was achievedby cutting a sectionout of the hollowcolumn section toinsert the kinked200m-diameterdownpipe and thenwelding it all upagain.

“All you see is asquare hollowsection columncoming down butthe amount of workthat went into it wasimmense,” saysRowecord’s RichardCherrington.

ISG seniorproject managerMike Jenner said:“The design conceptled to the decisionto use structuralsteelwork. Toachieve the project’sslenderness and getthe detailing correctwould have beenextremely difficultwith any otherframing material.”

In association with The BritishConstructional SteelworkAssociation and Tata Steel

The Crystal, a dramatic urban sustainabilitycentre built for Siemens in east London’sdocklands, uses an innovative steel frameworkto enable its complex crystalline form

By Pamela Buxton

Originally known as theSiemens Urban Sustain-ability Centre, this £30million building hasbeen renamed the

Crystal as the design of itseponymous faceted geometry hasevolved. According to Siemens,the shape is intended to representthe many facets of sustainabilityand the complexity of urban life.

Designed by Wilkinson EyreArchitects, the building is locatedon the western edge of the RoyalVictoria Dock in east London andis intended as a showcase for sus-tainable design for both businessesand the public.

The Crystal, which is nearingcompletion, will be Breeam Out-standing and LEED Platinum.Conceived as an exemplar projectfor sustainable construction, thisstructural steel-framed buildingincludes high-performance glaz-ing, PV panels and energy-efficientservices including a ground-sourceheat pump. Grey and black waterrecycling is expected to reducewater demand by 90%. Designedto be all electric, the building willbe able to operate free of fossilfuels. It will make use of a mixedmode ventilation strategy and,where seasonally possible, will be

The two parallelogram forms are linked by an internal street.

The Crystal is locatedbeside theRoyal VictoriaDock in east London.

The columns rotate through 90 degrees for greater rigidity.

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TAPERING COLUMNS

floor and is cranked to follow thegeometry of the main facets. The main structural componentsare formed of bespoke steel mul-lions which are approximately 2m apart.

Located within London’s GreenEnterprise District close to thenew cable car and the OlympicPark, the Crystal is on course tocomplete ahead of the Olympicsand will host the world’s largestexhibition focused on urban sus-tainability, which is expected toattract 100,000 visitors per year.The aim is that it will provide aglobal knowledge hub to help adiverse audience understand howto build better cities.

PROJECT TEAM

ClientSiemensArchitect Wilkinson Eyre Interior architectPringle BrandonMulti-disciplinary engineeringArupProject management/costconsultant Turner & TownsendMain contractor ISGSteelwork contractorRowecord Engineering

‘No piece of glass or angle of steelwork isthe same, whichis an interestingchallenge’

One side of the Crystalhouses an exhibition space,the other contains officesfor 250 Siemens staff.

The complex irregulargeometry of the building, with each column andbeam a different height orspan, led the design teamto consider many optionsfor the roof includingfanning and spider webapproaches before settlingon a diagonal solutionformed by seven portals.

The roof surface is in sixplanes with the outer onecantilevering out from thegrid of columns by amaximum 15m.

The roof plate is carriedby steel plate box girders,prefabricated and boltedtogether. These are shapedto match the stressdemands so are deeperwhere necessary andstronger and shallowerelsewhere to optimise theamount of steel plate used.

All the primarysteelwork includingcolumns and edge beamsare fabricated boxsections. Eighty-five percent of the roofconnections were weldedin situ, including the 72mlongest main rafters, whicharrived in two pieces.

“One of the biggestproblems was makingconnections work thatwould be aestheticallyacceptable,” says RichardCherrington, contractsmanager of steelworkcontractor Rowecord.

“We had to come up with some quiteimaginative welding.”

ROOF STRUCTURE

The roof structureof each “crystal” isa pattern ofdiagonal formscreated by sevenportals and 14columns.

The roof cantilevers up to 15m from the grid of steel columns.

LEVEL 1

LEVEL 2

Leeds Arena will be theUK’s first “supertheatre”,according to its architect,Populous. Under con-struction on a tight city-

centre site, the 12,300-seat venuewill host both music and sportsevents and feature a distinctivecranked and faceted steel-framedform.

American-style sports arenasusually have in–the-round orhorseshoe configurations, but the£60 million Leeds venue will bebased on a traditional theatre for-mat built on a much larger scaleaided by both an enhancedacoustic performance and a mas-sive 54m-long by 10.5m prosce-nium arch that supports one-thirdof the roof structure.

Leeds was one of the few Britishcities that didn’t have an arena. Thecouncil is developing the schemeto attract regeneration in the areasurrounding the Claypit Lane sitenorth of the city centre — the high-est part of the city.

The design takes advantage ofthe 8m drop in height across thesite to allow the arena to nestleslightly, reducing its visual impact.At the rear, it is bounded by the ringroad but the front will open on to apublic plaza.

Externally, the facade is facetedon a series of grid lines relating tothe geometry of the seating bowlwithin, where three tiers of seatinghang off the main structure, with a row of boxes between thelower/main and upper tiers.

Around the column-free bowlare a lower concourse and catering

facilities on the ground floor, and amain concourse on the second.VIP areas are on the third floorwith another concourse on thefourth. In the fan-shaped arrange-ment, all seats face the centre of theperformance area, with a longestdistance to the stage of 68m com-pared with a standard arena’s 95-110m.

“We wanted to create a cathe-dral-like experience,” says Popu-lous associate principal JohnRhodes.

The arena’s structure contains4,200 tonnes of steel. “A steelframe was a really good solution forthis building. We have some quitelong-span roofs and complicatedgeometries and overhangs and to

have created that in another mate-rial would have been very difficult,”says Arup associate director JimBell, adding that nothing on thebuilding was orthogonal.

“The building is a really nice balance between steel for the spanning and concrete as anacoustic barrier.”

At £4,800 per seat, the cost istwo-thirds that of a traditionalarena seat, according to Rhodes,who describes the building asrugged and economical. Crucialto achieving such a tight budgetwas the team’s use of a co-ordi-nated bim model estimated tohave saved a tenth of the overallbuilding cost, including £300,000on steelwork alone.

“Leeds Arena was designed ascompact as possible for specificvolumetric and acoustic purposes,so the thorough integration of allbuilt components was key,” saysproject architect Nuno Guerreiro.

The building is designed to beflexible enough to cater for all typesof events and formats with the helpof two floors of internal rigging

above the stage and a 60-tonneloading capacity.

The first 16 rows will beretractable to create room for athrust stage or mosh pit, and forsmaller events a curtain can bepulled around both sides to reducecapacity and create a more intimateatmosphere.

Externally, the honeycomb-likeelevation is conceived as a “kalei-doscope” of glass, mesh and metal“shingles” set at 45 degrees and ani-mated by a tracery of LEDs plusprojections tailored to suit theevent taking place. Windows arelocated to take advantage of keyviews over the city. Shingles fade towhite towards the top of the build-ing to reduce impact.

“The overall shape of the build-ing and the geometry of the steel-work was the most challengingpart,” says Robin Hamill, projectmanager at Fisher Engineering.“It didn’t lend itself to very easystructural steel detailing.”

Another issue was an acceler-ated timetable in order to procurethe steel in the most cost-effectiveway. The arena is due to completenext spring in time for a summer2013 opening.

PROJECT TEAM

ClientLeeds City CouncilLead architect PopulousStructural engineer ArupMain contractor BAM ConstructionSteelwork contractorFisher Engineering

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The external facade isfaceted on a series of gridlines which relate to theseating bowl inside. Three tiers of seating hangoff the main structure.

In association with The BritishConstructional SteelworkAssociation and Tata Steel

Thirteen trusses form themain skeleton of the roof, withspans ranging from 40m to72m, and up to 75 tonnes inweight. These were spliced inthe air and took 15 weeks toinstall.

The trusses span at 9mcentres with five spanning ontothe 54m-long proscenium archtruss, which was delivered tosite in 32 sections andassembled there ahead of a75-hour continuousinstallation.

When Arup joined the BAMConstruction project team,after first acting as technicaladviser to the council, one of itsfirst innovations was to reworkthe roof design. Originally thetrusses were combined, withtwo layers of expensive

acoustic cassette build-up. Arup’s more economical

solution was to make thetrusses deeper in combination,with a 150mm top layer of in-situ concrete and metaldecking that forms the roof.

A second internal acousticlayer of boards and insulationis positioned 1,250mm downfrom the concrete, thermallyisolated from the mainstructure.

In such a city-centrelocation, acoustic efficiencywas a high priority to limit theimpact of noise on thesurrounding area, so a similarapproach has been used forthe walls. Here there is a gapof 500mm between theexternal precast concrete andinternal walls.

“We increased the overallmass of the roof to make theacoustics work, pushing up thetrusses into the void andmaking them deeper so theycould take the significantmass,” says Arup’s Jim Bell.

A bravuraperformanceSteel-frame construction hasenabled Populous and Arup todeliver the complex geometries oftheir Leeds Arena to a tight budget

By Pamela Buxton

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Fifteen buttresses from themain steel structure enablethe building to crank at aheight of 30m.

Initially, the engineerslooked at making this part ofthe primary structure, but thispresented difficulties becauseof the interface with theglazing system, so the facadesare instead supported by asecondary structure.

“The main challenge wasthe geometry. Every elementwas inclined in two directionsand it’s very difficult to drawthat, which is where the powerof 3D modelling comes in,”

explains Arup’s Jim Bell.Because of the 45-degree

angle of the glazing system, alot of the steel connectionshad to be co-ordinated withinhidden connections. With thecrank creating an incline of 22degrees, drainage was also anissue, especially over theentrance where the audiencewould be vulnerable to rainrun-off.

The solution was a systemof hidden gutters andpipework within the tracery ofthe facade to take the wateraway to the sides and into therainwater storage system.

ROOF TRUSSES

CRANKED FACADE

‘A steel frame was a really goodsolution for the complicatedgeometries’

Above: The 22-degree inclineon the facadeuses a systemof concealedgutters andpipework to protect theaudience fromrain run-off.

Partial sectionshows how crankedcolumns form thebuilding’s exteriorshape.

Roof trusses were assembledon site and continuouslyinstalled over 75 hours.

Leeds Arena master model showing the steel skeleton.

The arenacontains4,200 tonnesof steel, whichenabled theteam to createlong-spanroofs andoverhangs.

ical 24- hour cycle. In thicker con-structions of 1.5m-2m, theresponse is seasonal. According toKing however, only a very thinskin — as little as 30-50mm — isneeded to moderate temperaturesover a 24 hour cycle for generalpurposes.

For thermal mass to work, theconcrete soffits must be exposed tothe air and not covered up — forexample with dry lining or a sus-

pended ceiling that would ther-mally isolate the concrete and limitits capacity to absorb excess heat.Instead, casting in provision forservice ducts allows the soffits tobe exposed, but this must beplanned in upfront to be an inte-gral part of the design.

Although high quality commer-cial buildings, such as AHMM’sAngel Building in north London,demonstrate the appeal of an

exposed concrete aesthetic, thereare many precast flooring systemsavailable with a finely finished sur-face. And King says that plasteringthe soffit doesn’t reduce thermalperformance greatly. Acousticmineral fibre baffles that hangdown from the ceiling are anothersolution where an exposed con-crete soffit is felt to be aestheticallyundesirable.

No-one is claiming that thermalmass in itself is a panacea — its fullpotential can only be exploitedwithin a considered whole build-ing environment strategy along-side factors such as building ori-entation, glazing and solar gain —but the building fabric can be usedto regulate internal temperatures.However, this is achieved mostsuccessfully only if it is consideredearly in the project by the wholedesign team, says Murphy.

“It’s important that architectstalk to building performance engi-neers when they start because wecan have a very beneficial effect onthe carbon performance of thebuilding without curtailing inno-vation in the design process.”

FOR MORE INFORMATIONwww.tatasteelconstruction.com/en/sustainability/thermal_mass/

Want to achieve ther-mal mass? You’llneed a concrete-framed building then,won’t you? Not

necessarily, say building en-gineering experts and the steelindustry — which is under-standably keen to show thatthermal mass can be usedsuccessfully within steel-framedbuildings too, despite commonperceptions to the contrary.

Indeed, in recent research by theBritish Constructional SteelworkAssociation and Tata Steel only 9%of respondents associated thermalmass with steel.

The capacity of buildings of allconstruction types to provide acomfortable and stable internalenvironment in the most energyefficient way possible is a growing

priority, given rising energy pricesand the projected increase in aver-age temperatures over the nextcentury due to climate change.

“It is a common misconceptionthat a building needs lots of con-crete or masonry to achieve ther-mal mass. In fact we only requirea thin skin of concrete or masonry,and this can be constructed on asteel frame every bit as easily as ona concrete frame, provided theconcrete or masonry surface isexposed directly to the internalenvironment,” says Edward Mur-phy, technical director of engineer-ing and development consultantMott MacDonald.

Doug King, visiting professor ofbuilding engineering physics atBath University and founder ofconsulting engineer King ShawAssociates, believes that buildingdesigners need to make more use

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Association and Tata Steel

ArchitectAssociated ArchitectsLocationAston, Birmingham Completion dateAutumn 2011

Birmingham Council’s new£38 million Woodcock Streetoffices in Aston provide22,000sq m ofaccommodation over fivefloors for more than 3,000Birmingham City Councilemployees.

To meet the fast projecttimetable, the architectdesigned a steel-framedstructure combined withexposed concrete floors toachieve the necessarythermal mass to reducemechanical cooling needs.

Open-plan office floorplates are arranged in threeaccommodation wings offour storeys each,interconnected by bridges.

A two-storey internalstreet acts as the primary

circulation route through thebuilding.

Built by main contractorThomas Vale, the projectexpects to achieve a BreeamExcellent rating, havingreduced CO2 emissions byaround 31%, compared tothe minimum standardsrequired for BuildingRegulations Part Lcompliance.

Sustainability featuresinclude CHP, rainwaterharvesting and brown roofs.

ArchitectFairhurst DesignLocationBlacon, Cheshire

Cheshire Police’s new 2800sq m headquartersaccommodates 120 combattraining spaces for staff and apublic inquiry area.

With a tight timetable todeliver the building, thedesign team chose a steel-framed building with a hollowcore deck to incorporate anexposed concrete soffit.According to engineering and development consultantMott MacDonald, thisproduced time and costefficiencies which savedapproximately four weeks intime and 5% on the cost ofthe frame.

“Buildingperformanceengineers canhave a beneficialeffect on carbonperformance”Edward Murphy

Architect+3 ArchitectureLocationSouth Shields, TynesideCompletion dateSummer 2012

One Trinity Green is a three-storey, managed workspacecontaining 41 office, workshopand hybrid units within a 2,700sq m structure. Itrecently won the Breeamaward for the mostsustainable office building inthe UK.

Thermal modelling was

undertaken to inform adetailed mathematicalsimulation of the building’sthermal environment. Thishighlighted the opportunity toachieve thermal mass bycombining the building’s steelframe with exposed concretefloors. The design team madethis a key part of the proposal,seeking to create the look andfeel of a “modern Victorianwarehouse”.

Using the building’s thermalmass was one of a number ofsustainability measures thatcontributed to a Breeam

Outstanding rating, with ascore of 87.77%. One TrinityGreen is Energy PerformanceCertificate A-rated, with a 20%improvement over therequirements of Part L.

The £5.1 million building isdue to open this summer andis being developed by SouthTyneside Council inpartnership withenvironmental organisationGroundwork South Tynesideand Newcastle. Fundingincluded £2,466,500 offinance from the EuropeanRegional Development Fund.

CASE STUDY ONE TRINITY GREEN

HOW THERMAL MASS WORKS

Steel steps up to satisfythermal mass demands

One Trinity Green won the Breeam award for the UK’s most sustainable office building.

‘We only require a thin skin of concrete or masonry, and this can be constructed every bit as easily on a steel frame’

The steel-framed building has a hollow core deck with anexposed concrete soffit.

Cheshire Police’s Blacon HQ.

The new Aston officesof Birmingham Councilare expected to achieveBreeam Excellent.

Birmingham Council’s steel-framed office has exposed concrete floors.

CASE STUDY CHESHIRE POLICE HEADQUARTERS

1 The structure allows the free flow of air across exposed surfaces2 Heat is stored in the structure by day and expelled at night by theflow of cool air across the exposed surfaces

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of thermal mass in buildings of allconstruction types, includinglightweight steel and timber aswell as concrete.

“I’d estimate that 40% of theenergy used to control tempera-ture in buildings is just wasted,”says King.

Of course there is nothing newabout thermal mass — theRomans after all were experts inexploiting it in hypocaust heatingsystems. But King says its appli-cation today is hampered by a lackof skills and understandingwithin the industry and educa-tion, although he does acknowl-edge that this is improving.

Fabric energy storageThermal mass — also known asfabric energy storage — is the abil-ity of the building fabric, in par-ticular the exposed concrete slab,to absorb excess heat, thusimproving thermal comfort andreducing the need for mechanicalcooling.

Over a 24-hour cycle, the con-crete can absorb and store heatduring times of peak tempera-ture, then release it later as inter-nal temperatures fall at night time.After the concrete has cooled suf-ficiently, it can re-absorb heatwhen temperatures rise again.Such an approach works best inbuildings, such as schools andoffices, which do not have round-the-clock occupancy, rather thanthose that do, such as hospitals.

Concrete is effective for this use because it readily absorbs heatby radiation, but its relatively low conductivity means the heat remains isolated within thematerial.

“You can warm concrete and itwill absorb an awful lot without itstemperature changing a greatdeal. If we can have that exposedin a point of direct contact withthe space, we can use it to absorbthe heat of sun, people, comput-ers and other electrical devices,”says Mott MacDonald’s Murphy.

The thickness of the concreteslab required is a moot point. A thickness of 100mm of concrete,which can be accommodated inboth steel and concrete buildings,is generally considered the opti-mum amount as long as the con-crete is exposed directly to theinternal environment, with thefirst 25mm playing the greatestrole.

Beyond 100mm, there is littlegain in thermal performance.King says it is a myth that thethicker the concrete, the more thethermal mass benefits over a typ-

CASE STUDY BIRMINGHAM CITY COUNCIL WOODCOCK STREET OFFICES

Despite belief to the contrary, thermalmass can be achieved in steel-framed as well as concrete buildings

By Pamela Buxton