Atmosphere, Kolkata

Atmosphere is conceptualized as an ultra-luxurious residential project with 80 villas and with a vision that each villa should be unique. The structure is an icon for its overall vision, the architecture expression and the engineering determination. Deya enthralls that moment of inspiration, and it make the dream float through the cloud to its destinations, into an amazing atmosphere

Setting up the squad
M N Consultants role was that of a structural engineer. Along, with concept designer web structure they had the responsibility of transforming the owner’s dream into working reality. There were various aspects of design like mep, architectural, infrastructure which had to be worked on with, and, create a structure which is suitable for all their needs and safe in all aspects of design.

Structural Aspects
A B+G+37 stories high rise condominium with ‘Deya’ the connecting bridge at a height of 100m from the Ground level. The magnificent hanging sculpture is intended to look a floating cloud between the peaks of the two towers. The structure will span more than 320 feet in width, 55,000 square feet of usable space having a silver lining façade featuring numerous kinetic discs. It comprises more than 1,500 steel sections with a total weight of 2340 tons, assembled 100 metres above the ground.

The structure had to straddle between two towers in a combination of a “beamlike “and a “catenary” system. The primary challenges facing the structural system includes 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 the primary structural considerations.

Challenges
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. To make 100 meter. bridge move independently without affecting behaviour of the building during the lateral movement was the biggest challenge. The second big challenge was to design a foundation system to cater to such huge lateral load.

 

Deya’ a bengali word used by the famous Nobel Laurette Rabindranath Tagore meaning heavenly cloud, and so is the name of the bridge, which is connecting the two towers in the sky in the form of a cloud. It’s a Great creation by the Architect, and not only an engineering marvel but a piece of art amidst clouds at a height of 110m. The concept of the structure behind this piece of art is also a unique in nature. The state of the art design and the concept of base isolation is truly a piece of engineering excellence. The fabrication and erection of the bridge had to be very precise and done with the help of state of the art technology. As a structural designer, guided by the Master Dr. Hossein Rezai-Jorabi, it’s an unforgettable and probably a lifetime experience for me.
Utpal Santra, Managing Director, M.N. Consultants Pvt. Ltd.

Specifications
The structural system is a steel space truss. The space truss is made-up by several distinctive components/hierarchies, each performing specific tasks:

  • Longitudinal Trusses: span between the two towers, and, form the main spine supporting the cloud structure.
  • Transverse Trusses: span between the longitudinal trusses, and, cantilever from them to form and support the actual cloud floor structure.
  • Floor Diagrid: provides lateral rigidity to the floor structure.
  • Horizontal Arches: control lateral movements of the cloud structure.
  • Crown: form the support for the floors and the roof at the ends of the cloud structure over the two towers.
  • External Diagrid: binds all the other components together to ensure they all work in unison.

 

The name Deya literally means the cloud, a cloud is a cloud, light and heavy at once… Deya has been visualized as a sky club seemingly floating between the two tall towers of Atmosphere. The designer’s challenge was to build something as solid and stable and yet be very light. Deya spans between two towers for a distance of 96 M, 72m being the effective span that measures between the two bearing supports. The longitudinal trusses forming the main span, further with transverse trusses, floor diagrid, horizontal arches, roof arches, crown, and, finally the external dia-grid which binds all these components together to ensure that they all work in unison. There are other five aspects of the project which when put together with the sky bridge make this whole thing rather complex or rather sophisticated structure. Firstly, structure of both the towers of Atmosphere needed a strong base to hold the sky bridge in any kind of weather. Secondly, using of UC steel sections of 356x406x1086, having thickness of 125mm and unit weight of 1086 Kg/m. Thirdly, there was a potential risk in movement of Sky Bridge. Every movement was monitored during lifting work. Additionally, Train gauges were proposed to provide at the tension supports. Fourthly, during lifting, vertical deflection were monitored and checked and manipulated with analytical results. Finally transferring the entire Sky Bridge load to 4nos Eradiquake Isolation Bearings placed two at each tower. Constructing Deya makes one realize the flexibility of the steel. From the lifting of the Sky bridge belly to erection of different layers; and finally completing the external façade elements including the fixing of the kinetic discs on the Deya skin, it has been a continuous challenge. Working and being a part of it has been an absolutely unforgettable, unique and extremely enriching; an enthralling experience
Krishnendu Ghosh, Deputy General Manager, Forum Projects Pvt Ltd

 

Exclusivity

The features of the project are:

  • The architectural design intent of the project.
  • The structural design itself has been absorbed to define the architecture.
  • The bridge connecting two 37 storey tower spanning 100 meters build with 2340 Mt of steel.
  • The bridge is not just a walkway it houses four floors which is unique in itself.
  • The tower has big cantilever terraces which was also a challenge to design and built.
  • The base isolation done using special bearing below the bridges.
  • The concept of bridge sitting on base isolation at the height of 120 meter.
  • Limiting and controlling the movements of the towers at the roof levels where the cloud structure is supported, while 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.
  • The way steel structure has been designed with combination of longitudinal and transverse truss along with binding by floor diagrid which is itself one of its kind.
  • The no of bolts, joints that have been provided in this project is really a big number to handle. Total number of welded joints = 1,090 Total number of splice joints = 1,317 Total number of bolts = 30,000

 

Fact File

  • Client: Forum Projects 
  • Architect: Arc Studio, Singapore & Practice Design Pvt. Ltd.
  • Structural Consultants: Web Structures & M.N. Consultants Pvt. Ltd.
  • Contractor: L&T
  • Steel Fabricator: Eversendai
  • Steel Tonnage: 2340MT

 

 

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