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niranjana • Apr 4, 2011

# Diagrid Structure In The Skyscrapers

Think new constructions, think sky scrapers. Most of the constructions coming up these days are skyscrapers. And of late one technology seems to be dominating the design of these skyscrapers. That is the diagrid structural systems. In this article I’ll give you an idea about what the diagrid is and how it serves the building.

Diagrids or diagonal grid is a design for constructing large buildings with steel that creates triangular structures with diagonal support beams. The diagrids act as a rigid shell and is considered a beam. It is made restrained by welding the joints or bolting them into triangles. This is because triangles have better rigidity and don’t fail easily. These triangles either straight or curved will be giving the structural system for the skyscrapers. Most of the diagrids we can see are placed at some angles. This allows easier natural flow of forces through the structure. This load path is also uninterrupted and continuous.

The picture in the right is shows a computer software result after analysis on a diagrid that was used in the construction of the CCTV tower, Beijing. The regions of blue have zero stresses in them. And the stresses increase as the color changes to red. So it is obvious from the result of analysis that the vertical and horizontal members don’t take any load it’s the diagonal members that pass the load in the downward direction.

The diagrids are used for the following reasons. It provides an unhindered flow of the load from the structure to the base. It also provides a structural rigidity and braces the structure. It allows the formation of various complex shapes in the buildings like curves, irregularities. It is split into triangles which is the strongest shape. It even takes the lateral loads easily into the triangulation network. It eliminates the need for perimeter columns. A central core column and some inner column would be sufficient for the load transfer. It reduces the amount of steel required. The structural failure is reduced in the skyscrapers.

These diagrids can be made of either steel or wood or a composite material (concrete with steel).  But the most preferably used material is the steel. The diagrids are used in various buildings but a lot more in the skyscrapers. Some buildings that used this technology are:
• Capital Gate, Abu Dhabi : It used the diagrid technology to use to enable the formation of the leaning, curved structure. It cannot be done using the conventional methods of columns and curtain walls. So this technology was a boon for this project.
• CCTV Tower, Beijing : It was a building that needed the diagrids to provide the proper support to the overhanging part and also brace the whole building.
• Hearst tower, New York.
• The Bow, Alberta. (under construction)
• Seattle Central Library, and many more.
Image Source: Design