Tall Buildings
Curbing Tall Building Sway: The New Paradigm
Tim Santi

“The primary benefits of incorporating a supplemental damping system in a tall building far outweigh the disadvantages.”

Supplemental damping systems are used in many different types of structures to mitigate and reduce vibrations. Such damping systems rely on various forms of energy dissipation to counteract energy imparted on a structure due to additional forces such as large crowds jumping on a cantilevered seating bowl or wind loads on a tall and slender building.

Historically, tall and slender buildings have been designed under the premise that a supplemental damping system is a last resort. Most tall building engineers would rather continue to increase the size of shear walls and supercolumns until wind-induced accelerations are reduced to acceptable levels than to plan for a supplemental damping system from the beginning.

Certainly, damping systems are not without their disadvantages. For example, supplemental damping systems often require a very large area near the top of a tower where real estate is prime, and damping systems are not necessarily conventional or regularly used. However, the primary benefits of incorporating a supplemental damping system in a tall building far outweigh the disadvantages for two important reasons. First, our experience with tall, flexible structures where damping systems were considered has shown that the total structural frame costs, including the cost of the damping system, are often much lower than the cost of the additional concrete and steel that would be required without a damping system. Second, the material quantities and size of the lateral system of the tower (shear walls, supercolumns, outriggers, braces, etc.) are significantly reduced when a supplemental damping system is leveraged, resulting in larger lettable area due to thinner shear walls and smaller columns, smaller dead load of the structure which further reduces shear wall, column, and foundation sizes, and finally, a much more sustainable approach.

Due to a variety of reasons such as advances in high-strength materials and construction technologies, tall buildings are becoming more and more slender and flexible, and structural cores are becoming smaller and smaller. As this occurs, supplemental damping systems will increasingly be given due consideration for these types of projects, and the notion of using a damping system only as a last resort will become a thing of the past.

Tim Santi / P.E.
Tim is a Principal and a Senior Project Manager specializing in tall building design with Walter P Moore’s Structures group in Atlanta, Georgia.