Our structural engineering team worked closely with Morphosis to stay true to the design intent – a challenge given some aspects of the tower’s design. Chief among these, the core of the building is shifted outside of and separated 32.8 feet from the office floor plate. Only narrow walkways were envisioned to link the core to the remaining tower mass. This could have created two incredibly slender towers, with insufficient lateral strength and stiffness.
To address this and other design challenges, our team designed an innovative “mega-braced” tube structure. Composite columns were linked by steel diagonal bracing organized over multistory modules around and through the tower. The result is a closed tube structure that achieves a high degree of efficiency by engaging the entire tower depth in resisting overturning forces. By using this bracing in lieu of more common concrete systems, the structure could be designed to the higher drift limits allowed for steel systems by Chinese code. This approach offered significant savings to the structure and helped keep it relatively light, particularly given its height.
The structural concept was fully integrated with the architectural design. This included fitting bracing through floor plans without compromising lease spaces, and also maintaining the minimal floor links, envisioned by Morphosis, between the tower and core through the use of light steel bracing at selected levels.
The structure is designed in accordance with the latest performance-based seismic design approaches using non-linear time history analyses, and received expert panel approval.