Decades before the age of megatall skyscrapers like the Burj Khalifa, Chicago boasted bragging rights as home of the world's tallest skyscraper with the Willis Tower (aka Sears Tower). However, if Perkins+Will's new project comes to fruition, the city may look forward to getting back in the record books with the world's tallest timber skyscraper.
Slated for Perkins+Will's ongoing Riverline development in Chicago, the River Beech Tower proposal is still very early in development so details are slim, but it would include 300 duplex units arranged around a central atrium. It would also feature indoor parks and other shared spaces.
Rising to 80-stories, River Beech Tower would dwarf wooden skyscrapers like the 21-story Haut and 18-story Brock Commons. Those two towers, and indeed many other timber towers today, are somewhat similar structurally and consist of prefabricated CLT (cross-laminated timber) sections, sometimes with added concrete cores.
Perkins+Will's approach is different, and could reach much taller heights than currently considered possible with timber by employing a diagrid system.
"The design is made possible by an innovative structural system engineered to take full advantage of timber's natural axial strength through an exterior diagrid system," explains Perkins+Will.
"This system efficiently distributes load across all the timber elements, engaging these elements for the tower's vertical and lateral load resistance. The diagrids along the tower's broad faces are linked by internal cross bracing at the edges of a large, central atrium. These braces create an interconnected system, allowing the external diagrids to work together to efficiently resist the lateral loads that dominate the structural design of very tall buildings."
It remains to be seen whether or not River Beech Tower will actually be built – the firm states only that it could be realized as part of the Riverline project – but it's no mere blue-sky rendering concept and engineering and structural research for the project is ongoing.
River Beech Tower is a collaboration between Perkins+Will, Thornton Tomasetti, and the University of Cambridge. The British university was also recently involved in another timber tower proposal for London.