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Redevelopment of the Lee GardensHotel – The Manulife Tower

Redevelopment of the Hilton Hotel –Cheung Kong Center

International Finance Center Tower 2

International Finance Center Tower 1 – RC core + RC perimeter columns configurationup to 23/F, 23/F to 38/F becomes a composite structure with columns & slabs in steel

Characteristic for buildings constructed in compositemanner in Hong Kong• Size of building usually very large – floor area ranging from1800 to 2500 sq m, total floor area from 80000 to 200000 sq m• Structural forms bear similarity – RC core as the inner tubeprovide rigidity, external frame with perimeter steelcolumns/edge beams, floor in composite deck with RC topping• Very few columns provided at base/lower level to createspacious lobby at Ground entrance• External bracing members are seldom used to avoid blockingof valuable exterior view. Belt truss and outrigger systems areused instead• Buildings usually consist of a very large and deep basement

IFC 2 – structural configuration of thetower with the first set of Transfer/BeltTruss on 6/F, mega-columns, edgebeams, floor deck. and the RC core

Connecting the steel frame tothe inner core as seen in theCheung Kong Center

External bracingDiagonal bracing on external wallseldom used in Hong Kong’sbuilding. The one as seen here isthe Shenzhen Shun Hing Plaza

A 5-level basement wasconstructed using topdownarrangement at thesame time together withthe IFC2 superstructure

Similar situation ofconstruction a deepbasement using topdownarrangementalso appeared in theCheung KongCenter project

Major elements in Composite Building StructuresCore wall• Serves as the major load taking element and to providerigidity to resist deflection caused by lateral load (wind)• Usually formed by mechanical-lifted formwork systemsuch as climb form or jump form• Connection provision such as anchor plate for steel beams,build-in bar couplers or starter bar box for slab, andanchor frame for outrigger, will be provided in the corewall during its construction

Systematics and ClassificationMonophyletic Group29Systematics and ClassificationParaphyletic Group3015

Manulife TowerForming the core wall usingtraditional timber formworkinside the basement levels

Climb form system for theconstruction of the core wall for theManulift Tower’s superstructure

International Finance CenterTower 2Climb form system for theconstruction of the core wall for theInternational Finance Center Tower 2

Anchor frame and connecting plateembedded in the core wall for furtherconnection to the external steel frame

Anchor frame used in the Shun Hing Square project in Shenzhen

Work deck of theClimb-form systemConnectingplate for steelfloor beamsStarter bar boxConnection arrangement provided in the core wall

Another view of the connection arrangement at the core wall cornerStarterbar box

Major elements in Composite Building StructuresStructural steel external frame• Composing of steel columns that tied onto the core wallby steel beams• Steel columns can be- in the form of H-section, square, rectangular orcircular section- in-fill with lightweight concrete to increase rigidityand fire resistance- in the form of composite with reinforcing steel barsencased with load-taking reinforced concrete- in the form of concrete-filled column design

Concrete filled steel column used inCheung Kong Center

Square sectioned columnsInlet forconcrete infill

Various forms of composite columns

Composite column composing ofthick fabricated steel section andencased with reinforced concrete

Composite columns forming themega-column for the IFC2

Composite columnencased with RCComposite column composingof H-section sub-stanchion

External steel column being erected & tied back onto core wall by steel beams

Connecting steel beams ontothe core wallBeams weld or boltconnectedonto the gussetplate anchored firmly intothe anchor palte/framewithin the core wall

Major elements in Composite Building StructuresFloor plate• Usually in the form of RC topping composite to steelbeams by shear studs• GI corrugated decking used as permanent form for theplacing of the RC topping• Floor plate is connected to the core wall by starter barsembedded in the core wall

Placing the steel deckonto the steel beams

Detail of the slab (beforeconcreting) with steel barsand shear stud to allow theforming of a firmcomposite with the beams

Starter barsConnecting composite slabwith the core wall and thecolumn using starter bars

Welding the shear stud ontothe steel joist to enable thefloor slab to form firmcomposite with the beams

Placing concrete to form the RC topping of the composite slab

Major elements in Composite Building StructuresTransfer truss• Common design in Hong Kong to provide a spaciousground lobby to a building by using the minimumnumber of columns at the lower floors to support theentire superstructure• Transfer truss is used to transfer the building loads fromthe upper columns down onto the main columns at lowerlevel• Transfer truss sometimes connected to the outrigger toincrease the rigidity of the building at lower levels

The arrangement of theTransfer Truss for theManulife Tower

Detail of the Transfer Truss located at3/F-4/F for the Cheung Kong Center

Erecting the transfer truss system –temporary support frame to be provided forinstalling the large-section truss members

Elevation and InstallationArrangement for the TransferTruss of Cheung Kong Center

Transfer Truss located at 6/F-8/F for theInternational Finance Center Tower 2

Construction zonefor core wallCore wall and buildingframe lapping zoneBuilding frameerection zone6/F-8/FTransfer TrussOverall structural/constructionarrangement of the IFC 2

Major elements in Composite Building StructuresBelt truss and Outrigger• Provided to building frame at interval every 20 to 25floors to allow building to regain its stiffness.• Often in the form of inclined bracing, stretching inward,outward or in “X” or “Y” configuration• An anchor frame is embedded in the core for connectingthe outrigger in order to cater for the strong pulling outtendency

Belt truss and outrigger systemsof Cheung Kong Center

Layout detail of the belt truss andoutrigger systems of Cheung Kong Center

Outrigger and the column connection detail

Overview of the belt truss systemCheung Kong Center

Installation of the belt truss atcarefully arranged sequence

Elevation detail of thecompleted outrigger andbelt truss system

Installation ofthe belt trussInternational Finance Center 2

Corner steel postembedded in the core wallOutriggerCompositecolumnThe outrigger connecting into the core wall in IFC 2

Installing the bracing frame for the outrigger using a retro-installation process –core wall cast in 2 phases with the bracing frame installed in between

Corner steel postembedded in the core wallEmbedding the anchor frame into the core wall

Sequential detail of theretro-installation process ofcasting the bracing frameinto the core wall

Connection detail of the outriggerand the mega-column – a devicesto control differential shorteningbetween the steel column and theRC core wall is introduced

Detail of the column shortening controldevices with the use of shimming packadjusted by hydraulic action

Similar column shortening controldevices was also provided in theCheung Kong Center’s design

Production concerns for the construction ofcomposite structureThe construction of composite structures in Hong Kong is verycomplicated in terms of their size and work nature. Thefollowings are some of the common problems oftenencountered.1. Site layout to cater for very congested site environment2. Simultaneous works3. Cranage requirements4. Provision of temporary work arrangement during construction5. Height and headroom problems6. Works at peak period7. Controlling of rain water during construction

Extremely complicated site layout during the construction – demolition of theold basement, foundation works, forming of the building core, erection of steelcolumn and constructing the ground slab worked almost at the same timeLee Garden Hotel redevelopment

Layout situation during the later stage of basement formation period

Layout situation during the ground slab formation and corewall construction period

Layout situation during the constructionperiod for the superstructure and thetop-down basement

Foundation for Hotel block andbasement access arrangementhad just commencedPodium and basementbelow was partiallycompletedConstruction of thesuperstructure up tothe typical cycleLayout arrangement for the IFC2 at its peakIFC 2

Layout as shown 4 months later

Working and handling ofmaterial at height

Core wall and steelframe worked atdifferent phases –A lapse of sometimesmore than 10 floorsmake access to thedeck level of the corewall very difficult

Temporary access provision inside the core wall

Delivery and liftingof steel members

Handling of very heavyfabricated components

Provision of lifting equipment forthe hoisting of heavy steelmembers as seen in “The Center”and “Manulife Tower” projects

Cranage provision in Cheung KongCenter – 2 luffing cranes with600Tm capacity was provided atcorner position of the core wall

Locating the cranesinside the core wall

Cranage demandThere are altogether about 26000 steel members (averageabout 0.9 ton) being used in the Cheung Kong Center.The construction period for the building frame takes about50 weeks. That means, the cranage requirement at average isabout 520 ton/week, or about 100 ton/day, excluding thelifting of other materials such as the decking sheet or usualreinforcing bars

Temporary work provision –Erection of a temporary steeltruss for the erection of veryheavy or large span elements

Erection of temporaryscaffold to carry outwelding works (to theoutrigger system of IFC 2)

Erection of temporarysuspended platform for thefinal installation of theoverhanging steel components

Slot opening on roofTemporary work arrangement –Formation of a slot opening in thestructure for the access of large andheavy components

Intensive use of dry wall makingwater-tightness become morecrucial in composite buildings

Fire Resisting treatment to steel incomposite/structural steel buildingsThese can be done either by• Encasing the structural steel elements with concrete• Covering the elements with fire resisting boarding(e.g. cement board)• Covering the element with fire resisting plaster(e.g. spray-on vermiculite/cement-base plaster)

Applying spray-on fireresisting plaster to exposedstructural steel members

Gate valve for theinfilling of lightweight concrete tosteel column (a wayto improveperformance of thecolumn under fire)Outrigger frame inCheung Kong Centerafter the applicationof fire resistingplaster material

Encasing the fire escape and lift shaftwith fire resisting board/partition

Encasing the steel beams withconcrete for fire resisting purpose

Concrete encasement to steel membersConcrete encasement is provided to steel column in order to:• Convert steel column into composite column• Increase the rigidity of the column• Make the column fire resisting

Steel column before encasedwith reinforced concrete

Encasing a column using traditionalmanual/timber formwork

Encasing a column usingsteel gang formwork

Encasing a column usingself-climbing formwork

Operation of the self-climbing formfor the composite column in IFC2

Future development of using structural steel orcomposite structures in Hong KongInstead of building very large and complex building usingcomposite manner, which resulted to very high cost inconstruction, the following ways may be adopted in orderto achieve more cost effective application of technology infuture.1. Use more simple and straight forward design like regular steelframe structure in grid layout2. Use more standardized components such as universal sections,lattice trusses or prefabricated standard sections in the design3. Apply more to other types of building structure/construction asin many developed country like Japan, USA, or even Korea andTaiwan4. Forming hybrid structure with other prefabricated elements

The use of standard structuralsteel members in construction

Convenient products in market allowingthe use of very cheap and effectiveready-install structural steel members toform various building systems

A hybrid structure in Melbourne, Australia with the mixed use ofPrecast concrete, cast-in-situ concrete and steel composite

Detail of the hybrid elements

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