Geotechnical Engineering Award of Excellence: Chapultepec Uno R-509, Mexico City
Rodolfo Ernesto Valles Mattox
Country Manager, Mexico
WSP, Mexico City
A Top-Town Construction Strategy
This 58-story Chapultepec Uno R-509 tower stands atop 12 basement levels that are contained in a rectangular perimeter crate, formed from reinforced concrete cast on site. Known as a “Milan Wall,” this structural element works as a very deep vertical support, with part of its stability and capacity provided by the floor slabs that are cast as the construction descends. These operate as a supporting lateral system for the wall itself. The floor system is simultaneously subjected to axial compressive forces from the terrain, as well as the bending effects generated by regular, sustained loads.
The arrangement of the basement columns does not match the positions of the tower columns, however, and the basement is not decoupled from the tower. The transfer of the superstructure discharges is taken by the thick Milan Walls through a specific internal reinforcement configuration, so that forces flow to the foundation and ultimately to the ground. Extension piles of reinforced concrete were formed below the foundation slab, working as friction pile walls that transmit large loads to a resistant strata of highly compressible soils.
The Milan Wall enabled a top-down construction of the basement so that, instead of waiting for the whole excavation process to be completed before starting construction, the basement was constructed while the excavation descended. The grade-level slab was the first to be cast, so the assembly of the upper tower superstructure could also begin before the basement levels were completed.