Eight engineers in the firm’s Chicago office contributed to the structural design of the 73-story skyscraper. The firm’s scope of work included schematic design, design development, participation in the expert panel review process through approval, and review of the construction documents prepared by the local design institute. WSP also served as the mechanical-electrical-plumbing-fire protection engineer and the vertical transportation engineer for the project.
“It is the tallest building in China with a steel-braced frame structure,” said Patrick Ragan, who served as lead engineer for the Hanking Center Tower lateral systems.
The award was presented to the Chicago structural design team during the NCSEA conference in Washington, D.C. on Oct. 13.
Hanking Center Tower is a commercial office building noted for its tall, thin and irregular shape; and at 1,150 feet in height, it is the world’s tallest detached core building. The external mega-braced frame structural system accommodated the distinct architectural form, which features a service core offset 33 feet from the rest of the floor plate and a structural form capable of resisting typhoon-level winds.
“The detached service core is a unique feature – the building is essentially composed of two towers that are too slender to stand on their own, but are are wrapped together into one structure with a big enough footprint to efficiently resist overturning forces,” Ragan said. “The narrow bridges that connect the two sides will create a really dramatic experience for the occupants.”
WSP worked closely with Morphosis, the architectural designer of the building, to develop a cost-effective structure that achieved the architectural design concept and minimized the structural impact on interior spaces.
Design work for the 1.2 million-square-foot tower began in January 2013, and the building topped out in December 2016. The building is now structurally completed, and occupancy is slated for 2018. It is the third tallest skyscraper in Shenzhen and the 51st tallest building in the world.
“I think it ended up being a very cool building, so it’s great to see it getting recognition at this level,” Ragan said.
To achieve the architectural design concept, Hanking Center Tower incorporated an innovative ‘mega-braced’ tube structure. Composite columns were linked by steel diagonal bracing organized over multi-story modules around and through the tower.
“This closed-tube structure engages the entire tower depth in resisting overturning forces, much more efficiently than it would as two separate slender towers,” Ragan said.
By using steel bracing rather than the more common concrete systems, the skyscraper was designed to higher drift limits than what is allowed by Chinese code for concrete structures, which reduced the amount of steel needed for the tower by nearly 25 percent.
Because of the building’s unusual features, one of the biggest challenges the WSP team faced was the expert panel review process. The expert panel consisted of nine engineers and professors from across China who were tasked with making sure every possible contingency was considered in the design before construction began.
“The panel’s job was to come up with additional rules that this particular building needed to follow, beyond what was required by the building codes,” Ragan said. “I think we did a reasonably good job of anticipating the panel’s major concerns and proactively responding to them.”
Full-scale testing of select nodes where the braces intersect were carried out to satisfy the panel’s concerns and alleviate initial requirements that would have made the tower design less efficient.
With its striking design, Hanking Center Tower – which also received the Progressive Architecture Award in 2016 from Architect magazine – stands out among the many supertall skyscrapers that have emerged on the Shenzhen skyline over the past 20 years.
“It’s the sort of building people will definitely remember when they see it, so I feel lucky to have played a role in its design,” Ragan said.