A portmanteau of diagonal grid, the diagrid is a visible architectural element of many world-famous buildings. Beyond its eye-catching aesthetic value, the framework of diagonally intersecting metal, concrete, and wood yields structural benefits. Providing strength and stiffness to buildings, particularly those with complex geometries, a diagrid framework requires less structural steel, by up to 25 percent, than a conventional steel frame.

30 St Mary Axe in London, image by Marcus Mitanis

The diagonal members support gravity loads and lateral forces instead of the usual vertical columns. Buildings that utilize the diagrid system are generally free of intrusive interior columns, giving way to large and open floor plans. When the steel members are sheathed in glazing, it not only highlights the unique structural elements of the building, but creates an environment with an abundance of natural light.

Hearst Tower in New York City, image by Marcus Mitanis

However, the diagrid system is very arduous to implement; complicated computer models and construction methods require experienced engineers, architects, and contractors. For steel diagrid structures, the prefabrication process can add significant costs to the project. Similarly, concrete diagrid structures require a vast amount of formwork.

The Bow in Calgary, image by Flickr Antoine 49 via Creative Commons

Award-winning British architect Norman Foster has earned a global reputation for his firm's diagrid-rich designs. The Hearst Tower in New York City — which utilizes 21 percent less steel than a typical design — is one of the most famous examples of a diagrid framework. Two of Foster's other designs, 30 St Mary Axe in London and The Bow in Calgary, are among the most lauded buildings in the world.

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