Pavarini McGovern was retained to build a new “transparent” 31-story boutique office tower utilizing the latest concrete construction technology.
The project site, located on the high-profile northeast corner of Fifth Avenue and 42nd Street — across the street from the New York Public Library — comprises of three building lots.
This prime site required a dynamic, elegant design to complement and respect the library, while completing the 42nd Street gateway to Fifth Avenue. The building’s glass curtainwall is transparent at the podium, with both a butt-glazed glass fin storefront and a point-glazed system at the main entrance atrium, which opens up the interior lobby and retail stores. The angled west façade of the building respects the historic Library façade, while the setback breaks the continuity of Fifth Avenue’s masonry façades.
The structure has a reinforced concrete structural system with additional safety features at the core and perimeter columns at the base. Floor-to-ceiling vision panels, coupled with the cantilevered office volume, provide inspiring views over the library and adjacent Bryant Park. A rectilinear “spine” element sheathed in a metal wall panel system, housing the building’s core of seven elevators and two fire stairs, provides visual support of the glass elements.
The site parameters dictated a side-loaded core set to the northeast corner of the building’s floor plan. The building structure is cast-in-place reinforced concrete with “hardened” cores that provide a level of building safety exceeding New York City building code requirements. The concrete structure also allows for the slenderness and elegance of the tower within such a small, constrained site.
A hardened concrete structure allows for thinner floor plates, which enabled architect KPF to fit in two additional floors. The floor plate configuration allows for a reduced number of columns and a 15ft cantilever at the tower, creating a column-free perimeter at the building’s primary south and west façades.
One of the construction teams’ biggest challenges was designing the curtainwall to accommodate both the inter-story live-load deflection at the cantilever and the inherent shrinkage of concrete structures. The amount of combined live-load deflection, shrinkage, and movement due to building sway is less than one inch.
The construction of 505 Fifth Avenue posed logistical challenge (even for New York) due to building’s footprint. The City’s Department of Transportation did not permit cranes and/or hoists outside the building property line at any time, so the tower crane and hoist inside the building structure.
While the project team was in the process of demolishing the existing 18-story building within the new 505 Fifth Avenue’s property lines, the team discovered that the existing structure shared a brick party wall with the adjacent building. With the assistance of the structural engineer the project team determined that by securing tie-rods back to the existing steel with three-foot channel turnbuckles – on an eight-foot-by-eight-foot grid – would properly secure the neighboring party wall in place and demolition could resume.
505 Fifth Avenue’s property line is located within 20 feet of a subway tunnel, which created a unique situation for the project team and the MTA-NYCT. The approved shoring/bracing submission to the MTA called for “rackers” and “dead men” along a 100-foot length of the perimeter foundation wall, which would affect the foundation schedule by approximately eight weeks. The team established an alternate method of shoring/bracing to lessen the eight-week impact by six weeks.
In an effort to avoid the additional costs associated with temporary switchgear (2000 amps) required for building construction, Pavarini McGovern engaged ConEd and determined that if Pavarini McGovern could re-route their network compartment power conduit into the switchgear room in a permanent fashion during the foundation scope, ConEd would provide the site with temporary power.