Building:   785 Eighth Avenue , New York, NY
Client:   Esplanade Capital
Architect:   Ismael Leyva Architects P.C.
Structure Type:   Concrete Structure
Project Category:   Residential Developments
Photos:   Click photos to enlarge

Ysrael A. Seinuk Area of Specialization:

High rise buildings

Project Award

2009 CIB Award of Merit New York Concrete Industry Board

Project Description

Architectural Description

Ismael Leyva introduces a boutique condominium building located at the juncture of Hell's Kitchen and a part of the City that never sleeps: Times Square. The site offers excellent views to the Hudson River, Downtown & Midtown Manhattan. The design is based on a 1:15 (width: height ratio) glass spire that soars upwards from its 23 feet street frontage on Eighth Avenue to a height of about 520 feet. This innovative concrete structure was clad in a butt-glazed Curtain Wall system in order to maximize the usable square footage inside an already skinny floor plate. A skillful use of architectural elements like curtain wall coupled with structural cantilevers allows increased floor area at the top of an otherwise fairly narrow building.

The curtain wall system maximizes views from the 122 residential units with a row of cascading glass balconies on the east and west facades which culminate in an iconic rooftop bulkhead transforming the building into a "glass artifact"; an homage to this City of Views. The undulating facade of steel and glass animates the building with its reflective qualities. The wood textured fins on the façade draw the viewer's attention skywards where the building is capped off by a dramatic bulkhead caged in glass which blends it back into the famous New York skyline.

The building offers amazing loft apartments donned in a very contemporary design vocabulary similar to its exterior skin. The narrow massing of the building allows apartments to have frontage on more than one facade. These glass pavilions are a landmark in the city's luxury lifestyle. The building offers great resident amenities including a gymnasium, spa facilities, tenant storage, party spaces and a serenely Zen courtyard. This courtyard offers a space for quiet contemplation or a ready extension to other vibrant areas of the building.

Structural Description

785 Eighth Avenue is a 43-story concrete residential building, 484 feet high at the top of the bulkhead roof, and 516 1/2 feet above ground level to the top of the triangular screen wall. The residential floor plate is 85 feet in the east-west direction and varies from 23 1/2 feet to 44 feet in the north-south direction. The gravity load-bearing system is composed of reinforced concrete columns and shearwalls. Floor slabs are typically 9" thick made of flat plate construction. The typical floor to floor heights are 10'-4". The floor height is 11'-7 1/2" below the 8th floor.

Because of its 15:1 slenderness ratio (max ratio 18:1), making this building one of the most slender structures in the world, the building was designed with due consideration given to its dynamic behavior. Designing an effective lateral system was a challenge, achieved by judicious placement of shear walls and the maximum possible utilization of slab-frame action. High strength concrete was used to increase stiffness, if not fully utilized for strength. Concrete strengths in the columns and shearwalls were 12,000 psi from foundation to the 21st floor, 10,000 psi from the 22nd to the 35th floor, and 8000 psi from the 36th floor to the roof.

With the shearwall as the main lateral resisting system, coordination with the architect was particularly essential in configuring the wall system, allowing the walls to traverse the building from north to south. The walls were allowed to meander through the apartment partitions. Coupling beams were used to connect many parts of the wall system being interrupted by doors and other openings through it.

To achieve our design objective of stiffening the building, walls running along the north and south property lines of the building were connected by three north-south walls from the foundation to the 9th floor. The north and south walls became the flanges of the "box system". Above the 9th floor, and up to the 30th floor, the shear wall system still traverses the entire short width of the building, but the south flange was opened up for the enclosed 270 sq.ft. of area using air rights from the adjacent property. This area cantilevers approximately 7 feet over the wall below. From the 31st floor up to the roof, one of the three north-south walls remained, projecting south of the elevator core which still connects to the north flange of the shearwall. Reinforcement was typical 60 ksi grade steel.

Designing such a tall and thin building in a challenging site and being able to maximize the use of space was the biggest feat achieved by the "785 Eighth Avenue" team. In this building, concrete is utilized to its full advantage, providing stiffness, weight and damping that are essential in designing not only for strength and stability, but also for acceptable perception of motion.