What began in 1962 as a functional-but-unassuming eight-story ware - house on Manhattan’s West Side has become the foundation of one of the most unexpected and fascinating projects in New York City today – the 26-floor Hudson Commons building. Over the years, the cast-in-place concrete building at 441 Ninth Av - enue has been reimagined; notably in the 1980s when it was converted into an office building that retained most of the architectural character from its original era. But it never experienced anything quite like its most recent transformation. When Cove Property Group acquired the commercial property in 2016, they envisioned a vertical expansion of the site to capitalize on the 2005 rezoning of Manhattan’s west side. That left the developer with a decision to make on the fate of the former warehouse: Would they demolish the old building and rebuild from a clean slate, or would they find a way to reposition the existing structure to meet their needs? Early site investigations showed that the robust structure was in good structural condition making it suitable for reuse. Thus, after weighing their options, Cove selected the most cost-efficient solution that would achieve the maximum rentable area: the rehabilitation, retrofitting and reuse of the existing structure. The existing building would add 17 floors and 300,000 square feet of commercial space, creating a sleek new steel and concrete office tower. Now that its transformation is complete, Hudson Commons emerges as a 26-floor, LEED Platinum Class A property that provides 700,000 square feet of rentable office space, topping out at 421 feet. The architect of the renovation and addition is Kohn Pederson Fox As - sociates (KPF), with WSP USA serving as the engineer of record. Mue - ser Rutledge Consulting Engineers (MRCE) served as the geotechnical consultant. The construction manager is Pavarini McGovern (PMG). Best of Both Worlds For the project to succeed, several challenges had to be addressed, from precise demolition procedures without the use of interior shoring, Hudson Commons: Historic Foundation Meets Modern Engineering in an Innovative Manhattan Overbuild By Joseph Provenza, AIA, P.E., LEED AP BD+C; Jeffrey Smilow, P.E., F. ASCE; Yujia Zhai, P.E., Motaz Elfahal, Ph.D., P.E.; and Gerardo Aguilar, Ph.D.
and retrofitting of the existing columns, slabs and foundation systems; to the articulation of the new building core. Shoring can be costly, so it was important to the owner that the project included a plan for shoring-free demolition of a 125- by 25-foot area throughout the existing building to accommodate the new core. In lieu of shoring, the existing slabs were reinforced with a combination of temporary and permanent steel members that provided the required support of the structure. The original structure is comprised of two-way concrete slabs on a 24- by 28-foot grid with drop panels, “mushroom” capitals, and a ma - sonry core providing lateral stability. The low-rise, massive building is representative of the 1960s. The addition takes the form of a sleek modern office tower, which speaks to the 14-acre Hudson Yards megaproject development rising to the west of Hudson Commons. By contrast, the subtle renovation of the original building, which reuses the existing wrap-around brick façade while upgrading the structure to meet current design and construction codes, will keep the project grounded in the context of the neighbor - hood and its 1960s roots. WSP faced several unprecedented challenges that demanded highly in - novative structural solutions if the vision developed by Cove and KPF was to be realized. The existing cast-in-place columns and footings required sizeable retrofits for the gravity loads imposed by the new tower above, and the existing roof slab required extensive retrofitting to accommodate a heavily landscaped amenity space. The most invasive feature, however, was the addition of a new reinforced concrete core linking existing and new construction that would provide the required lateral stability and stiffness for the new taller building.
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csengineermag.com
DECEMBER 2021
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