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Web Structures win Indian sky bridge contract

Engineering consultancy Web Structures wins contact to build cloud-like sky bridge in the Indian city of Kolkata.

Developer Forum Projects has appointed earthquake specialists Web Structures specialists to help create the stunning structure, the centrepiece of a £74.8M, 39-storey high-rise luxury apartment project.

Sitting 100m in the air, “Deya” - which means cloud - will connect two towers that will make up “Atmosphere” - the highest development in the city, designed by award-winning Singapore-based architect Arc Studio.

Suspended in the air like a cloud, it will have a clear span of 65m and its three storeys will house swimming pools, a gym, spa, squash and badminton courts, a jogging track and mini theatre. A golf driving range is planned. It includes an open-air party deck and amphitheatre, along with multiple lounges and spaces for gatherings.

Web Structures is bringing its expertise working on tall buildings around the globe to Deya, which will be lit by LED lamps at night and will have a ‘silver lining’ with 15,000 kinetic discs shimmering on its surface.

Part of the design process has been the creation of a mock-up in China. The 1/20th scale model has been used to help in the assembly and scaling of spaces.

“We have come up with a complex structural engineering solution to frame the space the architects have defined,” Web Structures group director Hossein Rezai.

“It comprises of more than 1,500 steel sections, with a total weight of 1,500t, which will be assembled 100m above ground. The structure has to straddle between two towers in a combination of a “beam-like” and a “catenary” system.”

“The primary challenges facing the structural system include fundamental issues of safety and serviceability, as well as the critical issue of constructing such a large structure some 40-floors up.”

“Limiting and controlling the movements of the towers at the roof levels where the cloud structure is supported, whilst maintaining serviceability of the towers and the sky-bridge under seismic loads and the high wind forces that prevail in Kolkata have been our primary structural considerations.”

Kolkata is in a Level 3 seismic zone, making it vulnerable to earthquake damage. It is also exposed to high wind speeds during monsoon storms.

“These conditions present a challenge in themselves. However, when supporting the bridge spanning 65m between them, the ability of the towers to deal with the force and movements caused by these elements becomes even more important,” added Rezai.

“As the towers can move independently from one another those movements must also be controlled so the sky-bridge can be safely supported. The supports have been designed to accommodate the movements.”

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