Location: New York, NY
Client: 785 Partners. LLC
Architect: Ismael Leyva Architects
Photo Credit: Ismael Leyva Architects
Awards: CIB Award of Merit - 2009

785 Eight Avenue is a 43-story concrete residential building, 484 feet high at the top of the bulkhead roof, and 516 ½ 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 ½ 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 ½” 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.

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.