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C

esar Pelli didnt set out todesign the tallest buildingin the world in 1991, butthats what he did when hecreated the twin Petronas

Towers, home to Petronas,the Malaysian govern-ments gas and oilcompany. In March 1996,

the structures were topped out, and tenantsstarted occupying the towers in early 1997.

Tower One houses Petronas, while office spacein Tower Two houses its subsidiaries and othermultinational corporations that lease space.

In 1998, the 1,483-foot (452-meter)Petronas Towers surpassed the 1,450-foot(442-meter) Sears Tower in Chicago as the

worlds tallest building. Part of the KualaLumpur City Centre (KLCC), the 88-story,cylindrical towers rise above a 1.5-million-square-foot (139,354-square-meter), mixed-occupancy space, which includes a multi-level retail mall, a petrochemical library, anart gallery, the 800-seat Dewan Filahar-monik Petronas Concert Hall, and afour-level underground parking garage. The

towers are connected at the 41st and 42ndfloors by a glass-encased pedestrian bridge558 feet (170 meters) above the ground.Each tower is topped by a 246-foot(75-meter) tapered pinnacle.

Such mixed-use spaces are becoming com-mon in tall buildings, a fact discussed recentlyat the Council on Tall Buildings and UrbanHabitat Sixth World Congress. Constructingmixed-use occupancies that conform to abuildings environment is also leading toincreased use of performance-based codes.

The Petronas Towers is a case in point. Asthe worlds tallest building, the twin structurescouldnt always conform to prescriptive codes,given their height. This led to unique egress

solutions using the elevators and skybridge.

Islamic design

KLCC managers and the designer wanted thebuildings to be uniquely Malaysian in style.

We tried to respond to the climate, thedominant Islamic culture, and the sense ofform and pattern in traditional Malaysianobjects, explains Pelli of Cesar Pelli andAssociates of Connecticut. Rather than makethe towers asymmetrical, like the World TradeCenter Towers in New York City, which arediagonally across from each other, Pelli used asymmetrical design.

The plans for the towers were based on thetraditional Islamic design of two interlockingsquares, creating a scalloped, eight-point starpattern. The repetitive nature of the pattern

throughout the structures is another aspect of

PHOTOGRAPHS: COURTESY OF CESAR PELLI AND ASSOCIATES66 NFPA JOURNAL MAY/JUNE 2001

PETRONAS TOWERS at a glance:

Height: 1,483 feet (452 meters)

Stories: 88

Total built-up area: 3.7 million square feet (342,760 square meters)

Amount of concrete used: 5,650,347 cubic feet (160,000 cubic meters)

Amount of steel used: 36,910 tonnes of beams, trusses, and reinforcement Height of skybridge: 558 feet (170 meters)

Length of skybridge: 191 feet (58.4 meters)

Number of elevators: 76 total; 29 double-deck high-speed passenger

elevators in each tower and 18 service lifts

Number of escalators: 10 in each tower

Source: KLCC.com

The buildings were designed to reflect Malaysian culture and climate. The Islamic eight-

point star pattern is repeated throughout the building, and sun shades projecting from the

top of the curtain wall provide shade from the tropical heat.

Denise Laitinen is managing editor of

NFPA Journal.

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MAY/JUNE 2001 NFPA JOURNAL 67

Islamic design. As the towers ascend, theyreset back six times,with the upper floors tiltingslightly inwards, completing the form.

These geometric traditions are muchmore important in Islamic countries than in

the West and are understood, perceived,and appreciated by everyone in their soci-ety, says Pelli.

Petronas Towers have caught the worldsattention. The buildings were awarded theAIA 2000 Honour Award for best architec-ture in the world by the American Institute ofArchitects (AIA). Hollywood came calling, as

well. The Towers were featured in the recentaction film Entrapment, starring Sean Con-nery and Catherine Zeta-Jones.

Jeff Godfredson, NFPAs director of Asia-Pacific Operations, calls Petronas Towers oneof the most spectacular buildings in the world.

Theyre massive, yet delicate.Local customs had to be incorporated into

the buildings design. For example, the plumb-ing was configured so that the toilets wereoriented away from Mecca. Even the size ofthe fire command room had to be worked outbetween designers and local customs.

The designers also found siting the buildinga challenge. When the structural design engi-neers,Thorton-Tomasetti, began drilling, theyencountered patches of limestone underneath

a top layer of hard clay. This would havemeant that the building would settle unevenly

with some of it resting on soil and some onlimestone. The engineers wound up movingthe building site nearly 200 feet (60 meters) tothe southwest, away from the limestone cliffs.

The foundation of each tower is composedof 1.1 million cubic feet (13,200 cubic meters)of reinforced concrete 15 feet (4.5 meters)thick, which weighs 35,881 tons (32,550tonnes). Each tower is supported by 104 recti-linear barette-bored piles, ranging from 197 to

377 feet (60 to 115 meters) deep.The towers rest on 16 columns spaced 26 to

33 feet (8 to 10 meters) apart, which form a150-foot (46-meter) diameter at the base.Although the columns are exposed on theinterior, theyre only slightly visible on theexterior since theyre enveloped within thecurtain wall. This allows for a clean site linefor the windows.

The race for the worlds tallest skyscrapersstarted in cold, northern cities, such asChicago and New York, where structures were

made of steel, and windows were large andmirrored to let in as much sunlight as possible.In a tropical environment, however, shade ismore important.

The Petronas Towers are composed of

5,650,347 cubic feet (160,000 cubic meters)of reinforced concrete clad with 699,654square feet (65,000 square meters) of stain-less steel curtain wall, creating multiplereflections that give the buildings a shim-mery appearance in the tropical sun.

Windows are still set in horizontal rows toprovide breathtaking views, but the 828,821square feet (77,000 square meters) of visionglass are arranged at heights somewhat lowerthan might be found in the United States.Sun shades project from the curtain walls tokeep out the intense heat. By creating shadeand shadow, the sun shades also give a tropi-cal feeling to the towers.

The perimeter frame and outer walls ofthe building are constructed primarily ofhigh-strength reinforced concrete to reduceswaying in high winds. Because of thethreat of monsoons and other storms, thelocal building code, Uniform BuildingBy-Laws, requires that buildings be ableto withstand 65-mile-per-hour (105-kilometer-per-hour) winds.

Protecting occupants

As with any structure, protecting the build-ing and its occupants, as well as keepingbusiness interruption to a minimum, werekey elements of the Petronas Towers firesafety design. But there were additional chal-lenges. In a country of 19 million people,traffic in Kuala Lumpur is often so congestedthat the local fire service, known as Bomba,could face delayed response times. Therefore,the fire safety systems were based on aninternal fire safety defense, with Bomba as a

second line of defense.The design of Petronas was going on at

the time of the World Trade Center bombingand investigation, says Ralph Transue,senior vice president of Rolf Jensen andAssociates (RJA). We looked at how thebuilding in Kuala Lumpur could survive suchan event. RJA prepared the overall fire pro-tection strategy for the Petronas Towers and

worked closely with Flack and Kurtz, theprojects mechanical and electrical engineers,to implement it.

RJA and other design teams worked witha local engineering firm in Malaysia todesign the fire protection system in accor-dance with NFPA 72, National Fire AlarmCode.

The fire alarm systems needed to be of thehighest integrity because of the size of thecomplex and the fact that response time ofthe fire department could be excessive due totraffic congestion, says Transue.

As a result, the fire alarm systems useClass A circuits that can survive a singlefault. Through redundant circuitry, the sig-nal can find an alternate path and stillsound the alarm.

Because the fire protection system featuresredundant back-up, there are two fire com-mand stations for each tower on the groundfloor near the main lobby. Each center isrelayed to the main command center, whereauthorities can respond to the entire building,including the retail mall.A local area network(LAN) station enables a single operator tomanage all three systems. Redundancy is builtinto the main fire command so that thenetworked system will remain functional evenif portions of it are destroyed in a fire orother disaster.

The systems operation at the fire com-mand center has a large graphic display panel

set up like a map of the building, with inter-active controls. If a fire were to occur in oneof the towers, the alarm would show up onthe display panel. Next to the panel are thepanels controls, whose operations also showup on the display panel. If the fan on the firefloor had to be switched off, for example, theswitch would be displayed on the panel.

Emergency communication systems use athree-channel, electrically supervised wiringsystem, which is zoned for selective commu-nications. The communications system is in

Malay, Chinese, and English.Its linked with how the evacuation plan

works. Each floor is a separate zone andwould be evacuated separately, says BillWebb, who was chief engineer at RJA at thetime of the Petronas Towers project and isnow CEO of Performance Technology Con-sulting.

Several emergency generators provideback-up for all the buildings emergency sys-tems. The diesel-powered generators, housedin remote fire compartments on the fifth

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floor, are designed to share loads, so that a sin-gle incident wont affect fire safety systems ineither tower.

Fire suppression

Both towers are fully sprinklered in accor-dance with NFPA 13, Installation ofSprinkler Systems.

The design team was U.S.-based, and theowner wanted state-of-the-art codes andstandards used, says Webb. It was felt thatNFPA 13 was the most technically proficientstandard for a building of that height.

Each tower has its own water reservoir in thebasement to increase reliability. The reservoirsare filled automatically from a city main.Standpipes are zoned with the sprinkler systemrisers, which are fed by common fire pumps.

Local authorities have codes that are basedon British standards, but they didnt addresshigh-rises of this height,which was one of thereasons NFPA standards were used for certainfire protection features, says Transue. Wehad to convince Malay officials to use firepumps instead of tanks up in the building.

When we calculated the tank size that wouldbe required, it wouldve taken up the entire topof the building. The alternative was to useNFPA codes for standpipes and pumps.

Since redundancy and reliability were

important fire protection issues, separate firepumps with back-up are used for each zone.In addition, hand-held hose lines have beenplaced throughout the building to be used bytrained building employees.

Smoke exhaust and pressurization systems

Maintaining the integrity of egress routes iscrucial in such tall buildings. As a result,designers created a system that calls forexhausting a fire floor. Because each floor ispressurized, those above and beneath the fire

floor would create negative pressure on thefloor of fire origin and in the air shafts servingthat floor. The exit stairs for the fire floor arealso pressurized. By keeping smoke on the firefloor and exhausting it from the building,unaffected floors wont have to be evacuateduntil necessary.

By exhausting from the fire floor, yourekeeping the fire floor at a lower pressure,thereby preventing smoke from spreading toother floors, says Webb. The exhaust doesntkeep the fire floor clear of smoke, but it does

prevent it from spreading to other floors.

Egress

It wasnt always possible to use prescriptivecodes in such a tall building, and an innov-

ative performance-based approach was usedfor egress. The Petronas Towers have 76elevators, which play a part in the emer-gency egress plan. Each tower has 29double-deck passenger elevators and 9 ser-vice elevators. Five shuttle elevators provideexpress service from the ground level to theupper floors. Of these five, three can oper-ate at the same time on back-up power.

The double-deck elevators, in which one cabsits above the other in the same frame, have amaximum capacity of 26 people per deck. Bysharing the same hoistway, the lifts maximizeuse of the core space and improve efficiency.

Each tower also has 10 escalators.The 160-foot (58-meter), bi-level skybridge

connecting the 41st and 42nd floors also servesas an important egress route and refuge area incase of fire. The glass-paneled bridge is steel-framed,with beams connected to columns thatbear on twin plate girders. Four steel tubes riseup from the 29th floor and are firmly attachedto the beams, supporting the 827-ton (750-tonne) bridge.At the 29th floor, the steel tubesserve as hip-like joints.

At each end of the skybridge, expansionjoints and sliding bearings allow the bridgeto adjust to different wind loads. If the tow-ers move in the same direction in windyconditions, the bridge moves with them. Ifthe towers move in opposite directions, thebridge remains stationary, although itsdesigned to withstand movement of 20inches (500 millimeters).

Continuous expansion joints are alsoused on floors 42 and 43 in the structure,facade, and roof on each side of the bridges

mid-point, thereby reducing girder flexingon the bridge glazing.This diminishes win-dow panel movement to half of the bridgespan, rather than the entire walkway.

The sky bridge serves as an integral part ofthe buildings egress design should a fire occuron the upper floors of either tower. The lob-bies at each end of the pedestrian bridge weredesigned as separate fire compartments, withseparate HVAC systems, and they serve astransfer levels for the elevators that go to theupper and lower floors. Using the skybridge

and the shuttle elevators, building staff canevacuate occupants horizontally or vertically,depending on need.

The sky lobbies can also serve as refugeareas. Evacuation plans call for phased evacu-

ations of occupants on, above, and below thefire floor. Total evacuation would be a daunt-ing and disruptive action.

We dont plan to evacuate the entirebuilding at once. It would be impractical,says Webb.

Since the occupancy loads on the upperfloors decrease with height, its estimatedthat it would take 40 to 48 seconds per floorto clear floors 79 through 86, for a total exittime of 13 to 14 minutes. Its estimated thatit would take 1.2 to 1.3 minutes a floor toclear the lower floors, for a total exit time of12 to 18 minutes.

The race isnt over

Petronas Towers may not hold the title ofworlds tallest building for long. Several otherAsian countries are planning even taller build-ings. At 1,533 feet (467 meters), therocket-shaped Lotte building in Pusan, SouthKorea, will be 50 feet (15 meters) taller thanPetronas when its completed in 2005. The

Taipai Financial Center in Taiwan will stand1,667 feet (508 meters), and the 95-story

Shanghai World Financial Center in Shang-hai, China, will be 1,507 feet (460 meters).Other buildings are proposed for Jakarta,

Japan, and Australia.Skyscrapers often find themselves sur-

rounded by many other tall buildings in acrowded skyline. For instance, the WorldFinancial Center in Shanghai will beerected in an area that already has at least80 buildings that are 40 stories or higher.While Kuala Lumpur has many high-rises, the Petronas Towers stand out, not

only for their height, but because theystand alone.

Unlike high-rises in other cities, whereyou see several buildings near each other, thePetronas Towers are the only high-rise on ahill, making them that much moreimpressive, says Godfredson.

MAY/JUNE 2001 NFPA JOURNAL 69