56 Leonard Street

New York City, United States

A tuned sloshing damper for a unique luxury residential tower in Tribeca

A 57-storey skyscraper in Manhattan, 56 Leonard Street features striking cantilevered blocks that its architects, Herzog & de Meuron, have described as “stacked houses in the sky.” 


  • The Challenge

    All very tall buildings sway in the wind. With a height of 821 feet, 56 Leonard Street would be susceptible to wind-induced movement that could become noticeable to its occupants – especially on its uppermost levels, where units tend to be most expensive. To prevent this problem and ensure occupant comfort in every part of the high-end development, the building’s designers turned to RWDI for both wind engineering analysis and a plan to mitigate swaying.

  • Our Approach

    We’ve produced customized damping solutions for tall and supertall buildings around the world. Each project has unique requirements defined by the local wind climate, the building’s structural and aerodynamic properties, its unique architectural features, and the economic imperatives associated with its design, construction and marketing. In the case of 56 Leonard, its designers’ architectural vision – the “stacked houses in the sky” – limited opportunities for structural and aerodynamic adaptations to reduce wind-induced movement. A supplementary damping system emerged as the best way to meet the development’s wind engineering imperatives while preserving its aesthetic character.

    Having used wind tunnel testing to gain insight into the movement the building would experience in windy conditions, we proposed a tuned sloshing damper (TSD): essentially a large, water-filled tank installed on the building’s upper floors. As the structure sways in the wind, the water naturally sloshes in the opposite direction, passively dampening the building’s movement.

    The TSD at 56 Leonard, which contains 150 tons of water, is longer on one dimension than the other, allowing us to tune it at two different frequencies in the two orthogonal directions. In order to ensure that the damper effectively removes energy from the structural system – as opposed to letting energy resonate back down into the building – paddles are installed inside the tank to create turbulence. When the water moves across the paddles and becomes turbulent, the energy is turned into heat, which simply dissipates into the water.

  • The Outcome

    The building was completed in 2017, and most of its units have been sold. When units were first made available in 2013, one of the tower’s penthouses sold for $47 million, the highest price ever paid for a residence south of Midtown Manhattan. Upon its completion, 56 Leonard was recognized with an Engineering Excellence Award from the American Council of Engineering Companies.