The Petronas Twin Towers (also known as the Petronas Towers or Twin Towers), in Kuala Lumpur, Malaysia were the world's tallest buildings, before being surpassed by the Taipei 101. However, the towers are still the tallest twin buildings and office building in the world. Tower 1 was built by Hazama Corporation and Tower 2 by Samsung Engineering & Construction and Kukdong Engineering & Construction (both of South Korea). They were the world's tallest buildings from 1998 to 2004 if measured from the level of the main entrance to the structural top, the original height reference used by the US-based Council on Tall Buildings and Urban Habitat from 1969 (three additional height categories were introduced as the tower neared completion in 1996).
Comparison with other towers
The Petronas Twin Towers were the tallest buildings in the world until Taipei 101, as measured to the top of their structural components (spires, but not antennas), took over the record. Spires are considered integral parts of the architectural design of buildings, to which changes would substantially change the appearance and design of the building, whereas antennas may be added or removed without such consequences. The Petronas Twin Towers remain the tallest twin buildings in the world.
The Sears Tower and the World Trade Center towers were each constructed with 110 occupied floors – 22 more than the Petronas Twin Towers’ 88 floors. The Sears Tower and the World Trade Center’s roofs and highest occupied floors substantially exceeded the height of the roof and highest floors of the Petronas Twin Towers. The Sears Tower’s tallest antenna is 75 m (246 ft) taller than the Petronas Twin Towers’ spires. However, in accordance to CTBUH regulations and guidelines, the antennas of the Sears Tower were not counted as part of its architectural features.Therefore, the Petronas Twin Towers exceed the official height of the Sears Tower by 10m, but the Sears Tower has more floors with occupied office space at a higher level.
Designed by Argentine-American architect César Pelli, the Petronas Towers were completed in 1998 and became the tallest buildings in the world on the date of completion. They were built on the site of Kuala Lumpur's race track. Because of the depth of the bedrock, the buildings were built on the world's deepest foundations. The 120-meter foundations were built by Bachy Soletanche, and required massive amounts of concrete.
The 88-floor towers are constructed largely of reinforced concrete, with a steel and glass façade.
Tower 2 was successfully completed by Samsung Engineering & Construction and Kukdong Engineering (both of South Korea). The builders of Tower 1, Hazama Corporation found a problem during the construction, the tower was estimated to lean 25mm on the ground with its own weight. While Hazama's work to fix the problem, Samsung and Kukdong completed their work. Finally, the Tower 2 construction team succeeded one month earlier than tower 1. Due to a lack of steel and the huge cost of importing steel, the towers were constructed on a cheaper radical design of super high-strength reinforced concrete. High-strength concrete is a material familiar to Asian contractors and twice as effective as steel in sway reduction; however, it makes the building twice as heavy on its foundation than a comparable steel building. Supported by 23-by-23 meter concrete cores and an outer ring of widely-spaced super columns, the towers use a sophisticated structural system that accommodates its slender profile and provides from 1300 to 2000 square metres of column-free office space per floor.
The towers feature a skybridge (constructed by Kukdong Engineering & Construction of South Korea) between the two towers on 41st and 42nd floors, which is the highest 2-story bridge in the world. The bridge is 170m above the ground and 58 m long, weighing 750 tons. The same floor is also known as the podium, since visitors desiring to go to higher levels have to change elevators here.
The skybridge also acts as a safety device, so that in the event of a fire or other emergency in one tower, tenants can evacuate by crossing the skybridge to the other tower. However, the total evacuation triggered by a bomb hoax on September 12, 2001 (the day after the September 11 attacks destroyed the Twin Towers of the World Trade Center in New York City) showed that the bridge would not be useful if both towers need to be emptied simultaneously, as the capacity of the staircases was insufficient for such an event. Plans thus call for the lifts to be used if both towers need to be evacuated, and a successful drill following the revised plan was conducted in 2005.