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Petronas Twin Towers

From vision to reality

MAN'S URGE to reach the skies is evident in the many monuments, both ancient and modern, that are scattered across the globe today. From the biblical Tower of Babel to Chicago's Sears Tower, we see evidence of man's attempt at scaling the firmament.

But while it's all very well to design and plan these skyscrapers, it's another to make them a reality. The Petronas Twin Towers project was to be a challenge of the century. Not only would it be the world's tallest towers, but to have two of them side by side - this would be a feat never attempted before by man.

Moreover, the sheer height - 451.9m, about a quarter of Gunung Tahan's height which stands at 2,186m - and weight of the 88-storey twin towers raised innumerable challenges in the local building industry. Foreign expertise would have to be brought in to benefit both the country and the people working on the project.

The Foundation

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The foundation took one whole year to complete; every step of its construction was a technological breakthrough.

The Twin Towers were planned to be built on the site of the former Selangor Turf Club which was flat, green land. But soil studies showed that the site where the buildings were originally planned for, proved unsuitable for the foundation due to the irregularities of the limestone bedrock below that's known as Kenny Hill soil.

Each tower was calculated to weigh 300,000 metric tonnes which would be spread over a large concrete slab called a mat. But that weight exerted 1,140 kilopascals (one kilopascal pressure is equivalent to 1kg exerting pressure on 1sq mm), exceeding the weight-bearing capacity of the soil and enough to cause the foundation to fail.

Moreover, soil tests showed that the bedrock under both towers started shallow, 15m down, but sloped sharply to more than 180m.

To support the immense weight, a depth of 21m (as high as a five-storey!) would have to be excavated for the basement. This also meant penetrating the bedrock at one end but not the other.

Installing concrete-filled piers at the deep end would be difficult, slow and expensive, exceeding normal construction practices. The piers' shortening over time would also produce unacceptable tower tilting. (See diagram a)

KLCCB (Kuala Lumpur City Centre Bhd), the developer of KLCC, finally decided to move the location 60m southeast of the initial site to achieve better support. Here, the bedrock was deeper, thus allowing the buildings to be firmly anchored in at least 55m of soil for each tower basement.

And instead of piers, it was decided an entirely different foundation system was needed. Friction piles (structures narrower than piers), reinforced by grout (a sand and cement mixture), were used. (See diagram b)

Excavation began in March 1993.

The contract for the foundation works was awarded to a consortium of French and local companies, Dragages-Bachy-First Nationwide Sdn Bhd.

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Every step of preparing the foundation was a technological breakthrough, says Arlida Ariff, then the planning manager of the overall KLCC project.

"To dig the foundation, we didn't use hammering in the conventional sense. Instead we excavated the ground using a combined technique of piling and raft foundation (like a big concrete slab); it was the first time the latter technique was being used in the country.

"With this technique, when you bore the piles in, instead of circular piles, rectangular or barrette ones were used. Barrette piles are bigger than circular piles, so we could put in fewer number of piles. This also increases the safety margin and poses fewer problems.

"That's because the bigger the pile is, the smaller the number we have to put in and the better its ability to withstand tension.

"Water was then used to clean and keep the bored hole intact until we poured the concrete in. Until a certain depth, drilling mud or bentonite (a kind of "clayish" liquid)

was used instead of water as it was a stronger substance which could do the job more effectively in deeper parts," explains Arlida who's now the general manager of KLCCB and project management consultant for Putrajaya Holdings Sdn Bhd.

It was also the first time that the Malaysian construction industry would witness the largest amount of concrete poured in its history - 13,200cu m (enough to build 130 double-storey link houses!).

The concrete was continuously poured into the hole for more than 52 hours in order to eliminate construction joints in the pile mat and achieve a smooth finish.

According to KLCCB general manager Hashimah Hashim, then the project manager of Tower One, the construction industry normally uses grade 30 or 40 concrete. For the towers, high-strength grade 80 concrete was used.

"The use of such high grade concrete was a transfer of technology from the USA which uses up to grade 110 in the construction industry," he says.

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From left: S. Ragupathy, Hashimah Hashim, M. Hilme Hassan and Mohamad A. Jamal.
--Picture by Abdul Rahman Senin

The building of the foundation, from the excavation to its completion, took 12 months to finish.

Superstructure

KLCCB decided to bring in two separate contruction teams for the Towers. The reason, according to Abdul Rahim Naim, chief operating officer of KLCCB, was that "we didn't want to put all eggs into one basket.

"We also wanted both contractors to learn from each other. Logistically and financially speaking, there were far more advantages in having two separate teams."

Besides, adds Arlida, the competition between both parties to see who'd do the job better was healthy.

Thus in 1994, contracts for the construction of the Twin Towers was awarded to two consortia. The Mayjaus Joint-Venture, led by Japan's Hazama Corporation, and made up of JA Jones Construction Co, MMC Engineering Services Sdn Bhd, Ho Hup Construction Co Bhd and Mitsubishi Corporation, won the contract for Tower One.

The contract for Tower Two and the skybridge was awarded to SKJ Joint Venture which was led by Samsung Engineering & Construction Co and comprised Kuk Dong Engineering & Construction Co Ltd and Syarikat Jasatera Sdn Bhd.

Once the foundation for Tower One was ready in March 1994, Hazama Corporation was mobilised. The construction of Tower Two by Samsung began a month later in April once the foundation was prepared.

Eiji Goto, manager of business promotion and marketing and Tomio Oda, general manager of Hazama Corporation, recalled that work started one month earlier on Tower One than Tower Two as the foundation for the former was already prepared.

According to them, nobody had much experience bulding beyond 300m in height!

"This called for new, highly sophisticated technology," says Oda in a recent interview in Kuala Lumpur.

The new techology included the first-ever GPS (Global Positioning Satellite) system used in the country to calculate the accuracy of the towers' vertical height. Computer technology which integrated and coordinated the mechanical, electrical and structural architectural drawings was also used.

Perhaps the most revolutionary step made was in using concrete instead of the conventional steel in the construction of the columns and core walls of the towers.

Hashimah explains that the Twin Towers deviated from most high-rise buildings in the world in that most buildings use steel members in its construction, but "we opted for concrete since it was a local material that could be produced easily."

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Horizontal `bullnose' and `teardrop' sun screen brackets provide shade for the building and give the appearance of a flowing silver ribbon

She adds that Malaysia is not as sophisticated in steel production as in concrete production which had ready labour for the industry.

"So we compromised by having steel beams for floors which could be made locally in established steel plants. In this way, we saved costs and brought in the steel industry into the project as well."

Besides, its ability to withstand vibrations (which is twice that of steel) made concrete a more ideal component than steel. Due to its mass, concrete could help dampen the natural tendency of tall buildings to sway in the wind.

The massive size of the construction also demanded a huge workforce.

During the peak period of the construction between July 1995

till early 1997, as many as 1,000 people worked on each tower!

KLCCB design manager, S. Ragupathy remembers this time well. "That was when the operation was in full swing and KLCC had about 4,000 workers working on numerous projects - including the park, Maxis Tower, etc."

As the towers soared higher, a temporary passenger and goods lift was erected at the side which reached 350m while the remaining height at its completion was reached via scaffolding and stairs.

It took 25 months and a week to complete Tower One, and 24 months for Tower Two.

Throughout the entire operation, KLCCB held weekly meetings with SKJ and Mayjaus separately. KLCCB itself had two separate project management teams for each tower that regularly exchanged notes during the construction. This was to coordinate the efforts of both SKJ and Mayjaus.

Going on the fast track

One of the most challenging tasks was to complete the towers within budget and on schedule.

One highlight of the construction was the completion of what is known as the "typical floors" in record time.

The floors up to the 73rd are identical in shape and design; hence the name "typical floors" and since the process of constructing these floors was repetitive and consistent, it also meant that this part of the construction would be the easiest to complete.

"We went on a fast track, meaning to say that construction was faster than usual," says Hashimah.

An example of this was the speed used to construct the floors. Each one was completed within four days, almost three times faster than the normal construction rate of up to 10 days to complete a floor.

According to Goto, the workers worked round-the-clock in three shifts, 24 hours a day, seven days a week. Floors with different designs took one to two weeks to complete depending on how major the disparities were.

The concrete core walls were placed in position first, followed by 16 columns joined by ring beams and then the concrete cantilevered slabs which would form the geometric shape. The steel beams and composite floor were placed in and lastly, the concrete staircase.

The annex

The construction of the annex (the small building attached to the main tower which is called a bustle) only began once level 19 of the tower was reached.

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The final countdown...lifting and erecting the pinnacle

Says Hashimah: "Due to the difference in weight, we could not build both tower and bustle together at the same time. Since the main tower was heavier, we had to build it ahead by 19 floors in order not to create stress on the ground.

"We were constantly monitoring every stage of the building; the precision was to the 0.001 mm in our building survey! We'd to check the verticality all the time. For every floor that was completed, we would go back 10 levels below to check how straight the building was."

Cladding

Cladding began once the building reached level nine in late 1994.

A total of 83,500sq m of stainless steel extrusions and 55,000sq m of laminated glass were used to clad the walls and realise architect Cesar Pelli's vision, which was that of a "multi-faceted diamond sparkling in the sun."

The contract for the external cladding of the towers was awarded to a consortium of Harmon Contract Asia Sdn Bhd, Lucksoon Metal Works and Nippon Light Metal.

Designed as a curtain wall exterior, the cladding comprised 33,000 panels in all; each panel is as high as one floor and spans ledge to ledge. Distinctive features of the curtain wall includes the horizontal "bullnoses" and the "teardrop" sun screen brackets which provided shade for the building. Both bullnose and teardrop give the appearance of a flowing silver ribbon around the building.

Laminated glass was preferred for its safety, sound insulation, durability and solar energy control. It also screens out most ultra-violet rays, hence protecting the interior from sun damage.

Like the typical floors, cladding was constructed using the four-day cycle system. Says design manager S. Ragupathy of KLCCB, all panels were interlocked and placed in a down-upwards position.

"The speed of the cladding also depended on the construction of the floors. Not all the floors were cladded as some had to be left open due to the lifting of materials and so forth."

But the cladding was halted briefly at one stage - level 30 - in order to make way for the main highlight of the building - the skybridge.

The pinnacle

The crowning glory to the twin towers were the pair of 73.5m-high steel pinnacles that would propel the towers to fame as the world's tallest building.

Each pinnacle comprised a mast, a spire ball and a ring ball; all were lifted piece by piece in place.

Feb 13, 1996 is another eventful day - the day when the construction of the pinnacle began. First the mast, which had 24 segments, were numbered and jack-lifted according to sequence. The ring ball, which consisted of 14 concentric tubes of differing diameters, was placed a third of the way up the mast. Finally, the spire ball, which was designed in 10 sections, was welded to the top of the pinnacle. (See diagram)

According to Hashimah, although both contractors started on the pinnacles simultaneously, Tower Two was completed six days earlier on March 5, 1996!

"For Tower One, they began building the pinnacle from both ends (they lifted the top half which was already assembled and started building from below so that the pinnacle would meet halfway) while Tower Two assembled it piece by piece until it was completed. It was a learning process for the contractors and engineers for both towers."

Another unique feature of the pinnacles was that they were cladded entirely in stainless steel which would be brushed using a hairline brush technique (very refined brush strokes which makes the steel shine) until it shone.

The intention, says Ragupathy, was to ensure that the light reflecting off the pinnacle was vertical so as to give the "illusion of greater height."

But it is no illusion that after 37 months of sheer hard work, ingenuity and determination, the country's latest monument to its "Malaysia Boleh" spirit is a reality that can truly stand tall and proud among the world's greatest edifices.

March 93 - Excavation work for the foundation begins.

March 94 - Foundation for Tower One is ready and construction begins for Tower One. Construction of Tower Two begins a month later in April. Construction of the cladding begins once the tower reaches level nine. Construction of the annexe begins once the tower reaches level 19.

May 95 - The pre-assembled skybridge arrives from Korea to the KLCC site.

7 Aug 95 - The lifting of the skybridge commences on this day.

10 Aug 95 - The skybridge is finally in place.

13 Feb 96 - Topping-up of both towers (everything's ready but the pinnacle)

Jacking up of pinnacles for both towers begins.

5 Mar 96 - Installation of pinnacle is completed for Tower Two.

11 Mar 96 - Installation of pinnacle is completed for Tower One.

June 96 - Cladding is completed.

April 96 - The Council of Tall Buildings and Urban Habitat of Pennsylvannia, United States declared it the world's tallest building.

Aug 31 99 - Official opening by Prime Minister Datuk Seri Dr Mahathir Mohamad.

 

Quotes

"I was thinking then how much I wish I could live in a place where I could show my family, that's what I built."

- Petronas Towers project manager M. Hilme Hassan explaining why he felt so fortunate to be part of the towers project management team. Before that, he'd been building offshore platforms in Sarawak

"It's amazing to walk about in the towers and have lunch at KLCC Suria, and remember what it used to look like when the whole place was under construction."

- Petronas Towers project manager Mohammad A. Jamal who remains with KLCCB, based in Tower Two

"In the script they had the building blown up. Don't want to give anyone any ideas...."

- KLCCB CEO Abdul Rahim Nain (jokingly) on the reason why 007 was denied entry for the filming of Tomorrow Never Dies

"I've had many heart-stopping moments during the building of the Twin Towers. Still do, when I think about resolving the traffic situation."

- KLCCB CEO Abdul Rahim Nain

"Sometimes all you can see are heads."

- KLCCB public relations manager Omana Nair describing the view from the skybridge of the park's wading pool during the weekends

 

IMPORTANT: This article was part of the Merdeka/Independence Day celebration in Malaysia by The Star Online (www.thestar.com.my). Excerpts are shown here for relevance.

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