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building, both internally and exter-nally. The sail profile was chosen toreflect the seafaring heritage of Dubai. The architecture and thestructure have been integrated inevery way possible so that each com-plement of the tower takes advantageof the other. Even the steel-framed

exoskeleton, the primary function of which is to provide horizontal stabili-ty to the structure, acts to please thesenses of the viewer. Furthermore,the placing of the tower on a man-made island 300 m offshore not onlyreinforced the sail concept, but alsohas the practical benefit of freeing upspace on shore for the other parts of the development. Another signifi-cant consideration was minimizing the impact of the tower’s shadow onthe adjacent resort.

Because WS Atkins & Partnersserved as both the CM and the archi-tect/engineer, the time for the over-all program was substantiallyreduced, with design and construc-tion kept under six years from initialpresentation of design concepts,through construction of the island,island substructure, shell, core and-hotel.

By Martin J. Ha lford andPaul J. Walter s

The instruction from the clientwas to design not just a hotel, but asignature building—one that wouldannounce, “Welcome to Dubai.” Theclient wanted a dramatic statementwith imagery that would immediatelyconjure up images of the city, inmuch the same way the Opera Housedoes for Sydney and the Eiffel Towerdoes for Paris.

Functionally, Burj Al Arab is partof the Jumeirah Beach Resort and issited on a man-made island 300 moffshore, which includes the “five-star,” 600-bedroom Jumeirah BeachHotel and the Wild Wadi Aquapark.

The building height is 321 m,making it the tallest hotel in theworld. The hotel includes, among other amenities, the worlds tallestatrium at 180 m in height, 202 luxu-ry suites laid out in V formation andan average of 158 m2 standard singleroom. It has 202 “seven-star” superluxury suites, each two stories high.

Burj Al Arab is an extraordinary

Modern Steel Construction / August 2000

Building Team

Architecture, Engineering,Construction Management &Landscaping: WS Atkins &Partners Overseas

Superstructure Contractor:Joint venture of Fletcher ofNew Zealand, Murray andRoberts of South Africa andlocally based Al Habtoor

Steel Fabricator: Genrec(10,000 tonnes)

Island Contractor: DutcoBalfour Beatty

Designing a

Landmark for theUnited Arab Emirates

Designing a

Landmark for theUnited Arab Emirates


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quake risk and consequently there is

the possibility of tremors in Dubaiduring a seismic event in Iran.

Thus, the BRE recommend thatbuildings in the region be designedto resist an earthquake of MM VIIintensity, which equates approxi-mately to a Zone 2 earthquake,according to the Uniform Building Code (UBC). This corresponds withthe both the requirements of theDubai Municipality and UBC Zone2B, therefore a seismic zone factor

of Z = 0.20 was adopted for thedesign.

Structural Analysis

A three dimensional finite ele-ment analysis of the entire towerstructure was undertaken using thein-house ASAS suite of programs.The walls and floors were modeled asplate elements and the steel-framedexoskeleton was modeled using beamelements.

Response spectrum methods wereused to determine the forces and dis-placements on the structure due toseismic loading and the wind loadswere scaled so that the overall shearand bending moment at the base of the building correlated with theresults of the force balance tests inthe wind tunnel.

ported on these piles, is 2.7 m thickreinforced concrete and the base-ment walls are typically 750 mmthick.

Superstruc ture

The vertical load bearing elementof the superstructure is made of areinforced concrete honeycomb of walls and floor slabs extending up toa height of 210 m. The accommoda-tion wings extend in a V formationbetween the main core at their inter-section and stair cores towards theirextremity. Structural steel withmetal deck composite floors are usedto frame the end suites, which can-tilever beyond the stair cores.

The front elevation of the tower,between the two wings, encloses theatrium and consists of a tensionedmembrane made from Teflon coatedfiberglass fabric.

The tower’s resistance to horizon-tal loading is provided by a combina-tion of its reinforced concrete struc-ture and exoskeleton. The latterconsists of two frames, one externalto each accommodation wing, con-nected at third points up the heightof the main concrete core. These arefounded on the concrete substructureat ground level, and extend up to aheight of 270 m, to support the mast.In combination with the main core,these exoskeleton frames provide lat-eral stability in the front to backdirection.

The rear braced frame comprisesthree tiers of cross bracing betweenthe stair cores located towards theends of the accommodation wings.The bracing is attached by large steelembedments into the concrete struc-ture of the stair cores, which providethe chords for the bracing systemresisting lateral loads in the side toside direction.

The front and rear legs of theexoskeleton consist of pairs of 3 mdeep by 1 m wide plate girders, lacedtogether with I sections, to form arectangular member approximately

A more det ai led model of th e

exoskeleton was used at a later stagein the design process to help with theassessment of risk regarding vortex-shedding induced oscillations of theupper section of the structure.

Island Construction and Substructure

The island is essentially a conven-tional rockbund with a single layerarmour system, lined internally witha geotextile membrane and hydrauli-cally filled with sand dredged from

the seabed offshore. The armour sys-tem comprises precast concrete“shed” units, manufactured by using white cement above the waterline toimprove appearance.

Temporary works were incorpo-rated within the island as it was builtto enable the three levels of base-ment to be constructed within theisland. Tubular steel piles were dri-ven into the seabed and incorporatedinto the perimeter rockbund. Within

the rockbund, and just outside thefuture line of the basement, a highmodulus sheet piled wall was con-structed and anchored back to thetubular piles. This enabled excava-tion of the fill within the sheet piledwall to be carried out to a depth of 11 m below pile carpet level.

The building is founded on 250bored piles, with each pile measuring 1500 mm in diameter. The raft, sup-

Modern Steel Construction / August 2000


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3 m by 6.5 m in plan. These legswere erected in 12 m lengths, bycraning in each plate girder section,temporarily bolting them into posi-tion, lifting in the lacings and bolting them up and, after final survey andalignment, welded to the plate girder

joints in situ.The rear braced frame is com-

prised of 1.7 m by 2.6 m stiffenedbox sections, erected in approximate-ly 12 m lengths, temporarily boltedtogether and then, after final surveyand alignment, welded together insitu. Due to the geometry and size of some of these elements, they had tobe lifted into position using a tandemcrane lift, which required extremelycareful planning and coordination on

site.

Fabr ic ation and Er ection

Three new self-climbing cranes,each with a capacity of 760 tonnemetres, were purchased to erect thesuperstructure. These were posi-tioned one in the main core and onenear the end of each accommodationwing, and climbed within the con-crete structure on specially fabricatedsteel grillages. The cranes were care-

fully selected and sited by the con-tractor in order to be able to coverthe entire building area and to beable to lift the majority of the large,heavy steel elements of the exoskele-ton and mast.

The cranes were used to lift cus-tom-made table forms for the mainfloors, 12 m by 8.5 m on plan andequal to the floor area of one suite. Also, taking full advantage of thehigh lifting capacity of the cranes,

the intermediate mezzanine floorswere pre-cast at ground level, adja-cent to the building and lifted intoplace by the cranes.

The majority of the structuralsteelwork for the tower was fabricat-ed by the contractor in South Africaand transported by ship to Jebel Aliport, about 25 km from the sitewhere a yard was set up to paint thesteel. The exceptions to this were the


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far as the centre of Dubai, some15 km away. With a floor plate of over 1000 m2, it is supported bytapered steel box sections up to1.7 m deep, cantilevering up to 27 mand anchored into the main concretecore by large steel embedments.

These embedments had a mass of upto 40 tonnes.

Due to the large cantileversinvolved, careful consideration hadto be paid to the erection methodolo-gy and presetting of the steelwork toensure that the completed structurewas level under the final dead load-ing.

Springing from the roof of thetower, with an elevation of 212 m, isthe helipad. This is a steel framedstructure supported by a 2 m deepbox shaped lattice truss. The helipadis anchored at one end into the mainconcrete core and at the outer end ispropped by two 1 m diameter steelcircular hollow sections. The helipadis designed to accommodate twin-engine helicopters, up to 7.5 tonnesin mass, for both VIP access and tosatisfy Civil Defense requirements asa means of escape in case of fire.

Projecting a further 60 m abovethe top of the exoskeleton, to aheight of 321 m above the level of the island, is the elliptical shapedmast formed from a stiffened steelplate tube, with slip-critical bolted joints between the 12 m long sec-tions. From the outset, it was realizedthat the mast would be vulnerable towind induced oscillations and, there-fore, a detailed analysis was carriedout to determine its natural frequen-cy and susceptibility to vortex shed-

ding and buffeting. The resulting natural frequency of around 1 Hzgives a windspeed typical of thatexpected on a daily basis in Dubai.The solution was to incorporatethree tuned mass dampers into theupper sections of the mast, to damp-en out oscillations in each directionof sway. Similar dampers were alsorequired in the upper parts of therear exoskeleton legs, to controloscillations.

diagonal elements of the exoskeletonthat, due to their design, had to befully constructed before erection.

Each diagonal was up to 85 m inlength with a mass of up to 165tonnes. Therefore, they were toolarge to be transported economicallyby ship and too heavy to be lifted bythe luffing cranes. These diagonalswere fabricated in Jebel Ali, and thentransported by road to the site in onepiece using special multi-axledwheeled bogies pulled by heavy trac-tor units. The diagonals were thenlifted and tilted into position on thestructure using strand jacks fixed tospecially made steel truss cathead

structures and then bolted, via tem-porary embedments, into the con-crete structure.

Skyview Restaurant, Helipadand the Mast

Near the top of the tower, thereare three structural elements of par-ticular note, the skyview restaurant,the helipad and the mast.

The skyview restaurant is a slen-der aerofoil shaped structure, whichprojects dramatically from the face of the building, 190 m above theground. It offers commanding viewsover the surrounding coastline and as


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