270 Park Avenue

New York City’s Largest Steel Structure and Tallest All-Electric Office Building

Located in midtown Manhattan on a full block bounded by Park Avenue to the east, Madison Avenue to the west, and East 47th and 48th Streets to the south and north, 270 Park Avenue building encloses 2.5 million sq. ft spread over 60 floors and reaches a height of 1,388 ft, the sixth tallest in the city. It is the new corporate headquarters for JPMorgan Chase and can accommodate up to 14,000 employees, four times the number in the Union Carbide building, which it replaces.

Challenging Foundation Constraints

The tracks and platforms of Grand Central Terminal and Grand Central Madison run beneath all but the western quarter of the site, leaving only the narrow gap between adjacent tracks for support. Severud Associates designed an innovative system of massive plate girders and fan-shaped steel columns that converge at forged steel nodes—the Tabletop—resting on concrete walls between the tracks. The walls bear on caissons drilled into bedrock at the lowest track level.

High Performance Concrete

The concentrated loads required higher strength concrete than was available at the time of design. Severud and the construction team engaged in a series of trial mixes, laboratory testing, and full-scale mock-up placements, eventually arriving at a reliable and affordable concrete mix with a 56-day compressive strength of 16,000 psi. As a bonus, the cement content is only about a third of the total cementitious material, reducing the concrete’s carbon footprint.

Elegant Lateral System

The lateral system for 270 Park Avenue consists of the ground floor and walls below; the Tabletop; the braced tower core; five levels of outrigger trusses; and the distinctive diamond-shaped macro-braces on the east and west facades. Working together, these elements carry the horizontal shears and moments from the superstructure to the foundation. An ingenious system of U-shaped, post-tensioned anchors dip to the bottom of the caisson caps to engage bedrock.

Effective Motion Control

The structural response of the building to wind loads was an important component of the design, which includes a mass damper to limit accelerations to exceedingly low levels. However, the building shares its foundation with two dozen railroad tracks, subjecting it to intense excitation with each passing train. Extensive modeling, analysis, and calibration using the existing building’s response to train-induced vibrations resulted in effective attenuation in the new building.

Conclusion

Design of a high-rise office building in New York City’s dense urban environment is difficult. Working with a site where a high-rise office tower already exists is an extra challenge. A location above active railroad tracks makes it nearly impossible. But with thorough study, extensive analysis, and enthusiastic collaboration, Severud Associates and the owner, design, and construction teams were able to pull it off—without significantly disrupting or altering the trains below.