The roof of the New International Airport for Mexico City is a lightweight steel shell structure and an architectural centerpiece of the new 4,432-hectare greenfield airport development. Visually exposed and structurally independent from the building beneath, it supports a 500,000m2 envelope that reaches a peak height of 45m above ground level and maximum span-to-depth ratio of nearly 60:1. While it is comprised of several subassemblies, including a 2-layer tetrahedral ball-node space frame and single-layer welded CHS shells, the roof was designed and detailed with the overt intent of achieving seamless visual continuity across the entire system. It is a mile long, nearly half a mile wide and is achieved with no movement joints.
The basis for the topological form is derived from a funicular shape, studied with hanging chain models and established through computational dynamic relaxation under pure vertical loading. Arup collaborated with the design architect, a joint venture of Foster + Partners and Fernando Romero Enterprise, to establish geometric parameters for the generation of efficient, buildable structural systems as part of the Architect’s integrated roof design. Simple geometric rules were developed to represent the detailed interaction requirements of members intersecting at each of more than 150,000 primary connection points.
To establish optimal sizes for more than 650,000 CHS members comprising the roof system, Arup developed a web-based application capable of analyzing a computational structural model and selecting appropriate member sizes from a catalog of available section profiles. Final member sizes reflect the result of myriad considerations, including internal forces from wind, seismic and hail events, deflection criteria, global stability, connection detailing and visual continuity.
Analysis of the roof structural model yielded a massive amount of data, and deriving useful insight from such a volume of results required a new method of information management. The Arup team structured the roof design process around a centralized database established on a local server running MySQL. Structural engineers quickly learned how to access and edit the database, and development of the design was carried out through the generation of relational datasets, rather than through conventional means such as drawings, schedules and spreadsheets.
The design team developed structural connections through a suite of typical connection details, which captured the design intent for forged space frame ball nodes and fully welded, unstiffened CHS connections. Development of connections was carried out in parallel with the process of fine tuning the roof form due to the high degree of interdependence between local and global geometry.
The complete design of the roof system was documented in the MySQL database and complemented with a relatively small set of versatile typical details. It was issued for construction in March of 2017 and work on site is presently ongoing with the building foundation level nearing completion and the first CHS roof megacolumns being erected.