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Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg at NIT Kurukshetra

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Technical paper by Jagmohan Garg and Drishti Batra on "Diagrid systems" presented at Civiera at Literati 2012 at NIT Kurukshetra.

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Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg at NIT Kurukshetra

  1. 1. DiaGrid Systems Structural System for Tall Buildings By: Drishti Batra Jagmohan Garg
  2. 2. What is DiaGrid? Diagrid (a portmanteau of diagonal grid) is a design • for constructing large buildings with steel that creates triangular structures with horizontal support rings. • Is a system of triangulated beams, straight or curved, and horizontal rings that together make up a structural system for a skyscraper • Similar in idea and execution to a typical moment frame - just more evolved
  3. 3. Examples of DiaGrid
  4. 4. Lateral Resisting System • This main structure is composed of RC Core and Steel Diagrid Column. • RC Core behaves like a Cantilever and Steel DiaGrid resists shear action. • Acting together they make the building stiff.
  5. 5. Member Design Plan o DiaGrid Columns – Behaves like 3- dimensional box resisting both Tension and Compression – Stress in DiaGrid Column under Gravity load and Lateral Load is shown in figure alongside:
  6. 6. o Corner Columns -Axial Forces transfer from the inclined column to corner columns. -Results in high stress concentration at corners. -Circular shape is more efficient for resisting buckling than square shaped corners.
  7. 7. o Perimeter Girders -They comprise of ring structure at the periphery of the building connected at the nodes which are further connected with the DiaGrid columns. First figure is with Corner Columns Second figure is without Corner Columns
  8. 8. Node Design • Under Vertical Load • Under Horizontal Shear
  9. 9. Node Design for Swiss Re Tower
  10. 10. o Tie Beams - Transfers load from RC Core to the DiaGrid Structures - Unbalanced forces can be resisted by ring beams and tie beams.
  11. 11. Construction Sequence • in-place steel shop welding • lifting up piece by piece • trial shop assembly of parts with high strength bolts • in-place welding • setting up perimeter girders
  12. 12. Materials Used • Steel -steel is the typical material of choice due to its high abilities to resist both tensile and compressive forces -usage of steel leads to complicated joints but now prefabrication of joints is widely done, so the problem is eliminated. • Concrete w/steel -expensive and slow construction
  13. 13. Design Studies
  14. 14. Difference between Conventional Exterior Braced Frame Structures and Diagrid structures • Conventional Vertical Columns are eliminated in DiaGrid Structures as compared to Conventional Structures. • DiaGrid Structures are much more effective in minimizing shear deformations. • In DiaGrid Structures, the core can be designed to carry only gravity loads without any bracings.
  15. 15. Relative Stiffness of DiaGrids and Braced Core
  16. 16. Benefits of Diagrid System • mostly column free exterior and interior generous amounts of day lighting due to dearth of interior columns and structure. • Diagrid Structure resists overturning. • roughly 1/5th reduction in steel possible • simple construction techniques • full exploitation of the structural material • easy and efficient distribution of load • free and clear, unique floor plans are possible • aesthetically dominate and expressive • economical for storeys upto 50-70.
  17. 17. Benefits of Redundancy in Diagrid Redundancy in the DiaGrid design is obvious • It is this redundancy then that can transfer load from a failed portion of the structure to another • Skyscraper structural failure, as it is such an important prominent topic, can be minimized in a DiaGrid design • A DiaGrid has better ability to redistribute load than a Moment Frame skyscraper. Therefore, there is deserved appeal for the DiaGrid in today’s landscape of building.
  18. 18. A Few Limitations • After 70 storeys, this system becomes uneconomical. • System comprises of complicated joints.
  19. 19. Conclusions DiaGrid structures are more stable than the conventional structures. They resist overturning because they provide maximum resistance against torsion. These increase the architectural beauty..
  20. 20. References • www.civilenggseminar.blogspot • MOON, K., CONNOR, J. J. and FERNANDEZ, J. E. (2007). Diagrid Structural Systems for Tall Buildings: Characteristics and Methodology for Preliminary Design, The Structural Design of Tall and Special Buildings, Vol. 16.2, pp 205-230. • MAURIZIO TORENO (2011). An overview on diagrid structures for tall buildings, Structural Engineers World Congress 2011. • www.nordicsteel2009 • www.dsg.fgg • www.sydney.edu.au
  21. 21. QUERIES?
  22. 22. THANK YOU!

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