Hummingbird Kinetics Damping System Installation
Originally known as the Atlantic Yards Building 2, this 35-story residential building located at 461 Dean Street in Brooklyn, NY was completed in 2016. It is shorter than most of the buildings equipped with a damping system, but wind tunnel tests determined that the structure may experience excessive wind-induced vibrations because of its slender shape and unusual structural system. The structure consists of 950 pre-fabricated steel modules stacked around four braced frames, rising to a height of 359 feet, making it the tallest modular building in the world. The contribution of the modules to the stiffness and damping of the structure was not precisely known. This meant the dampers had to be tunable to a relatively broad range of frequencies and damping ratios.
The building accelerations had to satisfy two comfort criteria: a 15 milli-g limit in the 10-year wind recommended by the Council on Tall Buildings and Urban Habitat (CTBUH), and a frequency dependent limit in the one year wind recommended by the International Organization for Standardization (ISO).
In collaboration with NASA, our team developed and implemented The Hummingbird®, a unique damping system solution for this project. It is a variation of a tuned liquid column gas damper that uses a system of water-filled pipes and independently tuned air springs to mitigate wind motion in tall buildings. Unlike traditional liquid dampers, 100 percent of the water mass in the Hummingbird® is active, which allows the Hummingbird® to provide equivalent damping with a lighter and smaller footprint. Also unlike traditional dampers, the Hummingbird®’s modular design is highly flexible and configurable, which allows the Hummingbird® to be distributed throughout the building.
The Hummingbird® dampers were prefabricated in a shop and affixed to their steel dunnage prior to shipping by truck. Upon arrival on site the system was then lifted up to the roof with the tower crane used to construct the building and bolted-down in their final position. The dampers were tuned to mitigate the response of the lateral and torsional modes that contribute to the acceleration in the short direction of the building.
Commissioning and full-scale performance monitoring was performed to demonstrate that the Hummingbird® system is fully functional and provides the motion reduction benefits to the tower precisely as planned.
Further Refinement of Hummingbird® Configuration … continuous improvement
Our team’s test laboratory was used for testing and fine-tuning the system components and geometry. This included component selection, dynamic fatigue cycle tests, system optimization, developing installation & tuning procedures.