Geotechnical Engineering Award of Excellence: Chapultepec Uno R-509, Mexico City

Rodolfo Ernesto Valles Mattox
Country Manager, Mexico
WSP, Mexico City

Top-Down Construction in a High-Seismicity Zone with Soft Soil Conditions

The 58-story Chapultepec Uno R-509 stands atop 12 basement levels on a narrow 26-meter-wide site in a high seismic zone. A rectangular perimeter crate, formed from reinforced concrete, cast-on-site diaphragm walls—known as Milan Walls—works as a deep vertical support for the tower. Stability and capacity are provided by the floor slabs that were cast as the construction descended in a top-down approach, but a robotized parking system required full openings across each basement level, interrupting the pressure path. This was resolved by a temporary bridge that was demolished after the top-down sequence was completed and a permanent bridging system was installed between floors. The grade-level slab was the first to be cast, providing a working platform during the construction.

Due to special requirements along the height of the tower, the column gridlines of the superstructure do not coincide with the substructure grid, so the superstructure concentrates and transfers loads to the perimeter columns, reducing internal foundation elements. An 8-meter-deep capping beam spreads the concentrated perimeter loads to the foundation diaphragm walls, and a horizontal thickened slab at the superstructure-substructure interface provides continuity to the seismic shears. Due to soft clay deposits and a very superficial water table, a recessed structural system supports an adjustable ground floor slab to allow for adjustments as the surrounding streets settle.

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