De-mystifying Diagrids: Expressive Structural System for Skyscrapers

Abstract

The word “diagrid” is a blend of the words “diagonal” and “grid” and refers to a structural system that is single thickness in nature and gains its structural integrity through triangulation. Diagrid structural systems have enabled significant transformation in the design of tall buildings. Diagrids are unique in their ability to assume the entire lateral and gravity loading of towers up to at least 50 storeys in height, eliminating the need for traditional columns and cores. Even in super-tall towers, it is possible to reduce or eliminate dependence on the core in the top 15–30%, allowing for unique spatial opportunities.Diagrids have rendered a particular elegance and lightness to buildings through efficiency, geometry and form. While other contemporary structural systems such as megaframes and outriggers are typically repressed in the detailing of the façade and dependent building elements, diagrids are chosen to form the basis of the architectural expression of the building.This article presents a methodology for the design of diagrid structures based on the systematic analysis of major buildings constructed from 2004 to the present as documented in Ref. in 2014. The design of diagrid towers will be demonstrated through primary choices in module size, member type, node design, function of the core and the desired expression in the façade system. These translate into additional concerns of constructability and customized fabrication. Fire control systems impact the ability to architecturally expose or conceal the steel, leading to detailing decisions.This article also looks at more recent trends in construction, such as the move away from optimization through increase in irregular modules, the use of composite construction and the potential inclusion of cast nodes.