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<strong>Construction</strong> <strong>and</strong> <strong>Per<strong>for</strong>mance</strong> <strong>of</strong><strong>Curtain</strong> <strong>Wall</strong> <strong>Systems</strong><strong>for</strong> <strong>Super</strong>-Highrise BuildingsPrepared byRaymond WM WongDivision <strong>of</strong> Building Science & Technology,City University <strong>of</strong> Hong Kong


What is curtain wallA curtain wall system is a lightweight exterior cladding whichis hung on the building structure, usually span from floor t<strong>of</strong>loor. It can provide a variety <strong>of</strong> exterior appearances but ischaracterized by narrowly spaced vertical <strong>and</strong> horizontalcaps with glass or metal infill panels.<strong>Curtain</strong> wall systems provide a finished exterior appearance<strong>and</strong> most <strong>of</strong>ten a semi-finished interior as well. They are alsodesigned to accommodate structural deflections, controlwind-driven rain <strong>and</strong> air leakage, minimize the effect <strong>of</strong>solar radiation <strong>and</strong> provide <strong>for</strong> maintenance-free long termper<strong>for</strong>mance. Most <strong>of</strong> today’s systems are constructed <strong>of</strong>lightweight aluminum alloys or steel sections


Development <strong>of</strong> <strong>Curtain</strong> <strong>Wall</strong> <strong>Systems</strong> inHong Kong1 st Generation – Early to late 1970’sfeatures: mainly non-proprietary products designby local window manufacturers.common systems: stick-type, sp<strong>and</strong>rel <strong>and</strong> cover,unit-in-frame typesmaterial: aluminum sections, fabricated locally<strong>and</strong> erected in-situ using manual means


Development <strong>of</strong> <strong>Curtain</strong> <strong>Wall</strong> <strong>Systems</strong> inHong Kong (Cont.)2nd Generation – Early 1980’s to early 90’sfeatures: mainly proprietary products usually inst<strong>and</strong>ard design out from the manufacturer’sinventorycommon systems: stick-type, sp<strong>and</strong>rel <strong>and</strong> cover,unit-in-frame <strong>and</strong> sometimes unitized typesmaterial: sections in aluminium or its alloys,fabricated overseas <strong>and</strong> delivered to site <strong>for</strong>installation.


Development <strong>of</strong> <strong>Curtain</strong> <strong>Wall</strong> <strong>Systems</strong> in HongKong (Cont.)3 rd Generation – mid 1990’s onwardfeatures: mainly proprietary or expert productsusually tailor-designed <strong>and</strong> made <strong>for</strong> highlyspecific purposescommon systems: majority are in unitized typesmaterial: sections in aluminum alloys, some instainless steel, large areas <strong>of</strong> glass was also used,large amount <strong>of</strong> accessories <strong>and</strong> fixing componentsare involved, components fabricated overseas (incl.China) <strong>and</strong> delivered to site <strong>for</strong> installation.


Use <strong>of</strong> <strong>Curtain</strong> <strong>Wall</strong> <strong>Systems</strong> in buildings1) Office buildings2) hotels3) Shopping centers4) Public/Functional buildings5) Residential buildings6) Other types


The city pr<strong>of</strong>ile <strong>of</strong> Hong Kong as viewed from theKowloon Peninsula. Generations <strong>of</strong> tall buildings sprungup from the harbour side since the 1970’s can be seen.


Aerial views <strong>of</strong> the downtownarea <strong>of</strong> Central District


Close up seeing the buildingfaçades <strong>of</strong> some high-risebuildings in downtown areas


Buildings using <strong>Curtain</strong>wall <strong>of</strong> the first generation- The <strong>of</strong>fice zone <strong>of</strong> EastTsim Sha Tsui developedin the late 1970’s


Merits <strong>of</strong> using curtain wall in buildings1) Can produce simple, neat <strong>and</strong> elegant building <strong>for</strong>m2) Can provide larger unobstructed exterior wall area3) Make the dead load <strong>of</strong> a building lighter due to theomission <strong>of</strong> solid external walls4) Reduce the use <strong>of</strong> <strong>for</strong>mwork <strong>and</strong> in-situ concrete duringconstruction5) Provide a reliable <strong>and</strong> almost maintenance-free externalenvelop <strong>for</strong> building


Common types <strong>of</strong> curtain wall systems <strong>for</strong>high-rise buildings1) Stick system2) Unit system3) Panel system4) Unit <strong>and</strong> mullion system5) Column-cover <strong>and</strong> sp<strong>and</strong>rel system6) Various types <strong>of</strong> glass wall system


Stick System<strong>Curtain</strong> wall in stick system is a cladding <strong>and</strong> exteriorwall system which is hung on the building structurefrom floor to floor. It is assembled from variouscomponents to include steel or aluminum anchors,mullions (vertical load taking member), rails visionglass, sp<strong>and</strong>rel panels, insulation <strong>and</strong> metal backingpans. For the fixing <strong>of</strong> the system, there are varioushardware components such as anchors, connectors,brackets, cramps, setting blocks, corner blocks,gaskets <strong>and</strong> sealants etc.


Glazing areaSp<strong>and</strong>rel areaTypical stick system wall –the Gateway at Tsim Sha Tsui


Unit SystemUnit systems are composed <strong>of</strong> modulated panels that arefabricated in factory <strong>and</strong> delivered to site in1-piece <strong>for</strong>installation. The panels are fully provided with all the glazing<strong>and</strong>/or the sp<strong>and</strong>rel panels, incorporated with the requiredinsulation <strong>and</strong> other architectural features, thus requiring verylimited 2 nd -fixed installation works on site.The panels are usually spanned in a floor-to-floor arrangement<strong>and</strong> may be designed in a number <strong>of</strong> st<strong>and</strong>ard/optional panelssuch as fully glazed, glazed with opaque panels, fully opaque inmetal or stone slab, louvered panels, or other special moduleslike the corner or bayed units. In order to get the best benefit <strong>of</strong>using this system, units are <strong>of</strong>ten produced to an optimisticlarge size so as to minimize the number <strong>of</strong> units used.


<strong>Curtain</strong> wall <strong>for</strong> theCyberport Office Blocks


Unit <strong>and</strong> mullion systemThis is a combination <strong>of</strong> the stick system <strong>and</strong> the unitsystem <strong>and</strong> may be regarded as a compromise <strong>of</strong> thetwo. It is more suitable <strong>for</strong> use in medium-sizedprojects so as to balance the factors <strong>of</strong> lead time, ease<strong>of</strong> installation <strong>and</strong> economy <strong>of</strong> scale.


Panel systemA panel curtain wall system is similar to a unit system, thedifference being that a panel system has homogeneous sheet orcast panel with few joints <strong>and</strong> may not have separate mullions.Unit systems are made up <strong>of</strong> smaller components fabricatedtogether to <strong>for</strong>m much complex panels that capable to per<strong>for</strong>mheavier duties or other more specific requirements. However,due to the relative simplicity <strong>of</strong> the system, curtain wall <strong>of</strong>panel system design may not be able to fulfill the usualrequirements most high-rise buildings required under HongKong’s environment. Its use is there<strong>for</strong>e more limited tocertain kinds <strong>of</strong> buildings like those <strong>of</strong> st<strong>and</strong>ardized design <strong>for</strong>low-income classes or <strong>for</strong> buildings <strong>of</strong> industrial purposes. Inthis case, the panels can be constructed <strong>of</strong> sheet materials <strong>and</strong>manufactured in large quantity in very low cost.


Column-cover-<strong>and</strong>-sp<strong>and</strong>rel systemColumn-cover-<strong>and</strong>-sp<strong>and</strong>rel system consists <strong>of</strong> columncovers, which are usually made <strong>of</strong> alloyed aluminum,metal sheet or other laminated/fibre-rein<strong>for</strong>ced sheet, <strong>and</strong>with glazing components <strong>and</strong> sp<strong>and</strong>rel panels that fitbetween them. It resembles certain similarity to a unit<strong>and</strong>-mullionsystem except that the structure <strong>of</strong> thebuilding is exemplified by the column covers.With the exception <strong>of</strong> the stick system <strong>and</strong> the unitsystem, other curtain wall systems are seldom used inHong Kong.


Structural glazing systemThe merit <strong>of</strong> using structural glazing system as external wallis to minimize the unglazed elements as much as possible,leaving glass panel almost as the only glazed surface on thewall. This can be done by providing larger mullion supportswhich span outward away from the structural floor <strong>of</strong> abuilding. Special clamping devices such as a spider bracketcan be used to hold the glazing panel in position. Structuralsealant is used to seal up the gap between the glazing panels.Structural glazing system <strong>of</strong>ten called also as the glass wall.It can sometimes be supported using a structural steel frameinstead <strong>of</strong> by the building frame itself thus easily give a free<strong>and</strong> open <strong>for</strong>m <strong>of</strong> design to building.


pGlass wall <strong>and</strong> skylight <strong>for</strong> the Festival Walk Shopping Mall


Glass wall <strong>for</strong> the TerminalBuilding at Hong Kong ChekLap Kok International Airport


pGlass wall used <strong>for</strong> theHong Kong Convention<strong>and</strong> Exhibition Center


Glass wall <strong>for</strong> theCyberport Development


The glass wall <strong>for</strong> theInternational Finance Center(Hong Kong Station)p


Glass Hubs at podium ro<strong>of</strong> <strong>of</strong> theInternational Finance Center


Glass <strong>Wall</strong> <strong>and</strong>Skylight used in theInternational FinanceCenter I Retail areas


Detail <strong>of</strong> the cablemullion/transom<strong>and</strong> spider clampWire mullion/Transom


Functions <strong>and</strong> per<strong>for</strong>mance requirements <strong>of</strong>curtain wall <strong>for</strong> high-rise buildingssituations where buildings in Hong Kong areexpected to face• Very large building envelop (say, up to 50000 sq m)• Typhoon situations (wind speed up to 60m/s)• Thunderstorm situations• Extreme temperature difference• Exposure to salty or polluted atmosphere• Long period <strong>of</strong> air-conditioning/cooling time


Functions <strong>and</strong> per<strong>for</strong>mance requirements <strong>of</strong>curtain wall <strong>for</strong> high-rise buildings1) strength <strong>and</strong> stability – dead load <strong>and</strong> wind load2) weather resistance – ability to keep out water & wind3) thermal insulation <strong>and</strong> condensation – max 30W/sq m4) sound insulation – 25dB or above5) fire resistance – usually no specific requirement ifenough separating distance from relevant boundary isprovided


Testing <strong>of</strong> curtain wall1) air infiltration2) water penetration under static & dynamic pressure3) structural adequacy under static & dynamic pressure4) vertical <strong>and</strong> horizontal seismic movement5) hinge <strong>and</strong> frame test6) in-situ pull-out test


Installation process1) transportation, storage <strong>and</strong> h<strong>and</strong>ling2) anchorage <strong>and</strong> connection provision3) installation arrangement4) final fixing <strong>and</strong> inspection


H<strong>and</strong>ling <strong>of</strong> thewindow units


Built-in anchor <strong>and</strong>hanging brackets


Detail <strong>of</strong> fixing (basicallyfixed onto build-in anchorby bolt <strong>and</strong> bracket)<strong>Wall</strong> fixing bracketwith 2-waydimensionadjusting slot


Inner lining to be provided in theinterior side <strong>of</strong> the curtain wall


Setting up <strong>of</strong> a mock-up wall section as sample be<strong>for</strong>e installation


Cases <strong>for</strong> References


Shun Hing Plaza- 68-storey <strong>of</strong>ficebuilding constructed incomposite <strong>for</strong>m (corewall plus external steelframe)


Installing <strong>of</strong> the curtain wall


Close up <strong>of</strong> the mullion frame at the external faces <strong>of</strong> building


Close up <strong>of</strong> thewalling frame withmullion <strong>and</strong>transom in position


<strong>Wall</strong> to cover thebracing memberslocated in thebuilding exterior


Fixing the mullion ontothe floor structure


Detail <strong>of</strong> the fixing bracket


<strong>Wall</strong> framing components


Manulife Tower(Lee Garden HotelRedevelopment) –50-storey <strong>of</strong>ficebuilding incompositeconstruction


Overview <strong>of</strong> the building’s exterior


<strong>Curtain</strong> wall installation<strong>for</strong> the typical floors


Close up <strong>of</strong> the rebate on the sides <strong>of</strong> the building exterior


Close up seeing the wallingarrangement <strong>of</strong> the sky garden


The hanger brackets <strong>and</strong> thesecured units on the floor edges


Transporting the wall unitsinto the building interiors


Placing the window unit into position


Close up <strong>of</strong> the st<strong>and</strong>ard units


The Center- A 80-storey <strong>of</strong>ficebuilding constructed instructural steel frame(mega-structure).


The configuration <strong>of</strong> the building frame


A separating line between the curtain wall <strong>and</strong> the building structure – worksuspended pending to the approval <strong>of</strong> the fixing detail


Gondola set up to facilitate theinstallation <strong>of</strong> the curtain wall units


Hanging, fixing <strong>and</strong>joining detail <strong>of</strong> the units


Pyramid feature atthe building corners


The backing structure <strong>of</strong>the pyramid feature


Detail <strong>of</strong> the backing frame be<strong>for</strong>e placing <strong>of</strong> the glass panes


Forming the invertedpyramid feature at one<strong>of</strong> the building corners


Seeing the window fromthe pyramid’s interior


<strong>Wall</strong> cleansing machine <strong>and</strong> the sliding door on the penthouse


Rail track <strong>for</strong> the hanging-typesliding door to provide a flushexterior look <strong>for</strong> an opening<strong>for</strong> the wall cleansing machine


Stretching out <strong>of</strong> thewall cleansing machinefrom a hydraulic arm


Close up detail <strong>of</strong> theautomatic cleansing robot thatmounted onto concealed trackprovided on the window units


Cheung Kong Center- A 62-storey <strong>of</strong>ficebuilding in compositeconstruction


Cheung KongCenter at night


Installing the curtain wall during the construction <strong>of</strong> the superstructure


Belt truss atbuilding top<strong>Curtain</strong> wall installation close to the building top


Belt-truss <strong>and</strong>Outrigger systemsTransfer Trusssystem


Backing frame <strong>for</strong> the louveredpanels at the transfer truss level


Installing the st<strong>and</strong>ardpanels on typical floors


Fixing detail <strong>of</strong> the panels


Fixing detail <strong>of</strong> the panels


Detail <strong>of</strong> the louvered panels


Exterior detail <strong>of</strong> the st<strong>and</strong>ard panels


Exterior detail <strong>of</strong>the st<strong>and</strong>ard panels


Elevation <strong>and</strong> sectional detail <strong>of</strong> typical panels


Enlarged detail <strong>of</strong> a typical panel unit


Storage arrangement <strong>of</strong> the panelunits inside building interior


Close up <strong>of</strong> st<strong>and</strong>ard panels seeing thesection <strong>and</strong> junction detail <strong>of</strong> the units


Stainless steel entrancecanopy <strong>for</strong>ming part <strong>of</strong>the building façades


ResidentialDevelopment atStubbs Road- A 66-storeyresidential buildingwith internal <strong>and</strong>external shear walls<strong>for</strong>ming the majorpart <strong>of</strong> the buildingstructure


Backing arrangement to thebuilding exterior be<strong>for</strong>e thefixing <strong>of</strong> the wall panelling


Detail <strong>of</strong> the built-in anchorchannel <strong>and</strong> the fixing bracket


Touching up <strong>of</strong> thewindow <strong>and</strong> wall units


Detail <strong>of</strong> the fixing atthe rebate window


Langham Place -Commercial Complex withhotel, retail <strong>and</strong> <strong>of</strong>fice block


Langham Place -Commercial Complex withhotel, retail <strong>and</strong> <strong>of</strong>fice block


Maintenance Considerationcommon problem sources where failures tocurtain wall <strong>of</strong>ten occurDesign failure – selection <strong>and</strong> appropriateness <strong>of</strong> thesystem, non-compliance to design <strong>and</strong> per<strong>for</strong>mancest<strong>and</strong>ards, imperfection in the jointing design <strong>and</strong>detailing, improper use <strong>of</strong> materials etc.<strong>Construction</strong> <strong>and</strong> structural failure – wrong locationor method <strong>of</strong> fixing, improper anchorage <strong>and</strong>connection provision (including failure in welding),failure in the walling components, unpredicteddeflection or de<strong>for</strong>mation appears in the backgroundstructure, poor supervision <strong>and</strong> workmanship.


Maintenance Considerationcommon problem sources where failures tocurtain wall <strong>of</strong>ten occur (cont.)Aging <strong>and</strong> deterioration – discolouring <strong>and</strong> surfacedamaging due to weather action; corrosion due to airpollution, acid rain, or electro-chemical effect todissimilar metals; aging <strong>and</strong> hardening <strong>of</strong> the glazingcompound or sealing gasket, deteriorating <strong>of</strong> theinsulating materials that lead to further dampening <strong>of</strong>the walling materials/components, disfiguring orloosening <strong>of</strong> the fixing <strong>and</strong> connections, loosening orbroken-<strong>of</strong>f <strong>of</strong> the glazing or other fitting items.


Maintenance ConsiderationSigns to observed during maintenance inspection-Sign <strong>of</strong> distress <strong>and</strong> deterioration <strong>of</strong> the entire wallsystem,- cracked, loose or missing glass panels,- bulging, bowing, separation, delamination, rotation,displacement <strong>of</strong> panels,- marks <strong>of</strong> water, staining <strong>and</strong> rust,- damaged <strong>and</strong> missing parts, corrosion, loosening orother defects,- extrusion, wrinkle, split, missing or other signs <strong>of</strong>deterioration <strong>of</strong> the sealing materials.- moisture appears around or behind the curtain wall.


End <strong>of</strong> Presentation

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