Kolkata: Tall residential buildings pass wind test unscathed
5/24/2020 4:38:00 PM
All the tall buildings in the city passed the Amphan test with only ornamental features like metal cladding and canopies being blown away by the express velocity winds. But two buildings in particular — the city’s only skyscraper The 42, and The Atmosphere which has a deck hanging between the twin towers, 152m above the ground — underwent a litmus test when Amphan came calling. And both passed with aplomb. All tall buildings are designed to sway in high velocity winds to prevent the pressure from buckling under the force. So when Amphan roared in at 133km/h, they swayed merrily for an hour. That left the building unscathed but left residents giddy with motion sickness. The swaying should have been considerable on the 61st floor of The 42, leaving residents violently sick. But a technology incorporated in the building was put to test on Wednesday evening. And it worked perfectly to ensure that the building didn’t rock. On the eve of the cyclone, a tank on the top floor was filled up with 120 tonne water. “The tower being very slender, it naturally sways quite a bit when there is heavy wind pressure or earthquake. But that would leave residents in extreme discomfort. To address the problem, a tuned liquid damper (TLD) tank was constructed at 246m, on the top most floor of the building. The TLD tank consists of two tanks, one atop the other separated by an intermediate baffle wall of 50% porosity. These tanks are filled with 120 tonne water. If the tower moves in a cyclone or earthquake, the water contained within the tank sloshes in the opposite direction of the tower’s movement due to rules of inertia. The load of the tank at the top of the tower thus compensates for the sway of the building,” explained Yashaswi Shroff of Alcove Realty, one of the companies in the consortium that developed the 250m building on Chowringhee. While several slim skyscrapers around the world use such TLD tanks, The 42 is the first building in Kolkata to put the technology into use. The building’s facade, including balcony railings and glass, held up in the wind whose speed would have reached 150km/h in the floors above. The facade was designed after wind-tunnel tests were carried out by RWDI, Canada and Windtech Consultants, Australia. “Façade design firm BES Consultants used the data to determine the structural strength required for various parts of the façade. After the cyclone, it’s completely intact,” said Shroff. At The Atmosphere, developer Rahul Saraf knew the cylone would test Deya, the triple deck hanging club in the air. But what he was concerned most was whether the palm trees atop could weather the storm. On Tuesday, the palms were reinforced. “The morning after the storm, it was devastating to see so many trees uprooted in the city. But thankfully, the palms had all survived,” said Saraf. Source: ET Realty
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