prado_extTopping out at 185 feet above street level, The Prado is the second tallest residential building constructed in the Golden Triangle area of Denver, Colorado. This is one of three luxury residential projects by the same developer that meet the demand for executive living in the heart of South Denver. Each project has similar aesthetic characteristics that easily identify a signature owner, and each utilizes concrete as the framing material of choice.

One of the developer’s requests was to have open terraces for as many units as possible. Achieving this required that virtually every floor have a different configuration. Concrete framing allowed tremendous flexibility with cantilevers, thus permitting over 55 percent of the units to have terraces. This was not only beneficial to the individual living space, but gave the building a stepping effect that greatly reduces bulk and allows sunlight to reach the street level.

The 18 stories of The Prado house three levels of above grade parking, ground floor retail space, and 108 residential units. Complications from a high water table allowed only a single level of parking below grade. The overall building dimensions are 180-by-140-feet at the base, and step back to 130-by-80-feet at the roof.

Due to Denver zoning requirements that limit buildings to a height of 200 feet, approximately 150,000 square feet of residential space had to be packed within 15 stories. This was accomplished by utilizing a 9-inch thick post-tensioned concrete flat plate on the residential floors. A composite steel floor system was not used because it would have required more than twice the floor depth than the post-tensioned slab to span the typical 28-by-27 feet 6-inch bays. Larger floor to floor heights would have resulted in two fewer floors and 12,000 square feet less saleable area.

A 10-inch thick concrete flat plate with mild reinforcing is used on the parking floors. Typical columns are 24-by-24-inches with reinforcement ratios ranging from 1 to 6 percent. Mechanical couplers were used to splice the longitudinal bars for reinforcement ratios in the 4 to 6 percent range. At the transfer level, 2 feet wide by 4 feet deep post-tensioned transfer girders support seven floors from above.

Concrete shear walls are used as the lateral force resisting system. The wall thickness is 16 inches from the foundation to the 11th floor, and 12 inches from the 11th floor to the roof.

The columns are supported on 2- to 4-feet diameter drilled piers that penetrate bedrock at approximately 15 feet below grade. The shear walls are supported on 5-foot 6-inch thick mats with 4-foot diameter drilled piers.

A 5,000-psi concrete mix with Type I cement and 3/4-inch aggregate was specified for the slabs, columns, and shear walls. A similar 4,000-psi mix was used for foundation walls and pier caps.

In addition to satisfying the requirements noted above, concrete framing provides superior acoustic performance, which is very important for residential applications. The concrete walls and slabs reduce sound transmission and provide an acoustic separation that far exceeds the requirements of the building code. Also, significant savings were realized compared to the steel alternative, since the lower floor to floor heights with concrete framing meant shorter vertical runs for the facade, vertical transportation, and all other utilities. Furthermore, additional fireproofing and finished ceilings were not needed with the concrete system.

The Prado adds to the district a neo-historic form that will continue to enrich this area for many years to come.

Credits

Owner/Developer:
Prado Condominium Corporation, Denver, Colorado

Architect:
Blue Sky Studio, P.C., Denver, Colorado

Structural Engineer:
Martin Design, Inc., Denver, Colorado

General Contractor:
The Weitz Company, Denver, Colorado

Architectural Precast:
Nostalgic Stone, Denver, Colorado

Forming Subcontractor:
Concrete Forming Associate., Denver, Colorado

Year:

2002