Senior Vice President
WSP, New York City
In the last few years, New York City has seen an explosion of residential developments of slender and very slender towers, including Central Park Tower (217 West 57th), 111 West 57th Street, 53 West 53rd Street (MoMA Tower), 432 Park Avenue, Sutton 58, 15 Hudson Yards and 56 Leonard. The towers listed range from 845 feet (257 meters) to 1,550 feet (472 meters) in height, and from 1:10 to an amazing 1:24 slenderness ratio. The combination of the height and slenderness of these structures results in very long natural periods and low inherent damping. A notable consequence of the dynamic properties of the towers is that both critical wind speeds and serviceability-level drift due to wind-induced motion, both directly associated with occupant comfort, have posed significant structural engineering challenges. A solution to these challenges has been the incorporation of supplemental damping systems, but this approach, in turn, presents its owns challenges. A comparison of a selected sample of slender and super-slender structures in New York City focuses on the design and performance of their supplemental damping systems. Other building characteristics such as building massing, slenderness, overall structure, and wind load demands present additional challenges, particularly the estimated versus measured natural periods and inherent structural damping.