Explore: High Rise Design Expertise
Motion Perception
The dynamic response of a tall building generally increases with wind speed and with increased building slenderness (higher building aspect ratios). As discussed in the Wind Engineering Integration section, in some situations building response to dynamic wind loading can be significantly magnified for a given wind event. When this magnification occurs for wind speeds in the range of 1-year to 10-year wind events, motion perception of occupants may be a concern. This is the range of wind events for which there is industry-standard performance limits established.
Generally, horizontal accelerations vary inversely proportional to generalized mass, inversely proportional to the square root of damping, and are less significantly correlated to the stiffness and the period of the structure. As a result, often the most cost-effective way to reduce building accelerations is by re-proportioning building elements to maximize generalized mass. If this cannot be achieved in a cost-effective manner, a more efficient way to meet acceleration limits may be to incorporate a building damper.
In order to maximize the efficiency of the devices, dampers are often located in the upper portions of structures. Damper sizes, as a rule of thumb, are about 2% the size of the Generalized Mass of the building and can take on many different forms. A few different types of building dampers are: (1) Sliding Mass, (2) Pendulum, (3) Liquid Column, and (4) Sloshing Tank. Halvorson and Partners has incorporated damping devices into two high-rise buildings in Chicago. The Elysian Tower and 50 East Chestnut are the only two buildings in Chicago which utilize Sloshing Tank Damper devices at the tops of the buildings to control accelerations. In the future with the emphasis on Green Architecture and Sustainable Design HP anticipates this type of technology will become more prevalent given the focus on using less material to meet performance criteria limits. Damping devices by definition minimize the amount of required structure and as a result HP is committed to staying at the forefront of damper design and implementation.
