Jingyu Lee

Magnusson Klemencic Associates

Reimagined Office Tower Using Cantilevered Trusses

The demand for office space is at an all-time high. According to the commercial real estate development association, NAIOP, there has been an 11 percent increase in the number of commercial office buildings in urban sites and a 14 percent increase in floor space since 2010. Building an office high-rise in an urban site, however, has many challenges. For example, architects need to address how to bring in more daylight and create a welcoming public space on the ground floor. Additionally, owners want to increase outside views and create premium, high-yield rental space. Finally, fabricators and contractors must consider how to increase construction speed using less material.

These challenges inspired the concept of the “cantilevered truss frame”- a visionary modular construction system that creates column-free, rapidly constructed, premium office space in an urban site. The cantilevered truss frame is a simple Pratt truss with a 13 foot depth and a 38 foot cantilever. The depth to length ratio is well below the typical 1:3 ratio. This creates an unobstructed view with no columns at the perimeter of the building. Every other floor is also set back 14 feet, introducing a double height space that brings more natural light to the interior.

The cantilevered truss frame and the steel plate core are pre-fabricated at an off-site fabrication shop. Because the truss and core are made of steel, the construction time is significantly less compared to a traditional concrete core system where one must wait for the concrete to cure. This results in lower construction costs and more rental income for the owners.

Since there are no perimeter columns, the ground floor becomes column-free. This means fewer total construction materials, with less steel column tonnage, and no need for extra concrete footings. At the same time, this system creates the opportunity for both public and landscaped areas in an urban site.