The Petronas Towers were shifted 61 metres off a buried cliff
Test boreholes under the old Kuala Lumpur racecourse revealed an unpleasant surprise: the planned footprint straddled the edge of an underground cliff, half decayed limestone and half soft rock. Rather than gamble, planners moved the whole site 61 metres so both towers would rest entirely on soft rock, then drove piles to world-record depths.
With bedrock so deep, the towers sit on the deepest foundations ever built at the time: 104 concrete piles bored between 60 and 114 metres into the ground. On top of them, each tower's raft took 13,200 cubic metres of concrete poured nonstop for 54 hours, a slab 4.6 metres thick weighing 32,500 tonnes that held the record for the largest concrete pour until 2007. Excavation alone meant hauling 500 truckloads of earth away every night.
Designed by Cesar Pelli, the 88-storey towers reach 451.9 metres and were the world's tallest buildings from 1998 until Taipei 101 overtook them in 2004. Importing steel was costly, so the structure relies on super high-strength reinforced concrete, which resists sway twice as well as steel but doubles the load on the foundations. The floor plan is based on the Rub el Hizb, an eight-pointed Islamic star, with curved sections added to create office space.
The government demanded completion within six years, so each tower got its own builder: a Japanese consortium led by Hazama on the west tower and a South Korean group led by Samsung C&T on the east, which reached the record height first. When one batch of concrete failed a strength test, work halted at a cost of 700,000 US dollars a day. Only one floor proved faulty and was demolished, and three separate on-site plants were then set up so a bad batch could never stop the job again.
Linking the towers at the 41st and 42nd floors is a double-deck skybridge, 170 metres up and 750 tonnes in weight, lifted into place over three days in July 1995. The lifts are double-deckers too: the lower car serves even floors, the upper car odd ones.
Source: Petronas Towers
