Managing the Stiffness and Sway of a Supertall Tower with a Stretched, Hexagonal Plan: Qingdao Hai Tian Center, Qingdao
Session: Track D: Structural Engineering Award: Part 1
Chief Structural Engineer, CCDI Group
Founder and President, AKAIA Architecture
New York City
The Qingdao Hai Tian Center development’s central and tallest tower features a frame-core tube system that has complementary deformation characteristics and simple and clear force transmission. Since the ratio of the length to width of the tower plan is nearly 2:1, several key techniques were utilized to ensure the stiffness of the length and width matched.
To reduce the vertical stiffness of the long direction, a large hole was opened in the core. To increase the vertical stiffness of the short direction, holes were arranged to avoid the widest walls and columns. To increase the lateral stiffness along the short direction, outrigger trusses were set in each reinforcement layer between its outer frame columns and the core, and waist trusses were set between its outer frame columns. To reduce the lateral stiffness of the long direction and improve the mechanical performance and redundancy of the structure, waist trusses were only set between the outer frames of the upper three reinforcement layers (out of a total of five).
Additionally, two tuned sloshing dampers were added to the fire water tanks at the top of the tallest tower to improve the comfort of the building under wind load. Thanks to the dampers, the wind-induced acceleration of the building is reduced by about 30 percent in different recurrence periods. In the 10-year recurrence period, the peak value of wind-induced acceleration is reduced from 17 milli-g to 12 milli-g, and the wind-induced vibrating comfort in the 1-year recurrence period is also greatly improved.