Architects Push the Limits of Old Materials in New Construction
Featured in Banker & Tradesman | April, 15, 2018
A few years ago, during my time as an associate at an architectural, urban planning and engineering firm, I was the lead technical designer on Poly International Plaza (Poly) in Beijing, China. The client wanted an iconic building, something that people would be forced to talk about. Such a request might sound like unabashed vanity to the uninitiated, but in architecture, apologies for these sky-high expectations are rarely heard. Vanity, after all, is often what pushes architects and designers to do their very best work. If you’re not trying to stand out and be the best, how could you possibly distinguish yourself and set your work apart? For cities looking to attract iconic international companies, an iconic building is an absolute must. Standard architecture is simply not enough.
The results at Poly were impressive. Thirty-two stories tall and inspired by Chinese paper lanterns, the main tower’s exterior is an elongated ellipse formed by a continuous exterior structural diagrid, with a jewel-like faceting of the double-skinned façade.
Pushing Material to its Limits
There was a time when the use of glass and aluminum in buildings as just an enclosure element was seen as new and innovative, creating buildings in the iconic “International Style” of Walter Gropius or Mies van der Rohe. But as technology advances, so does the architectural industry. Today the use of these materials is not just relegated to simple façades, using flat shapes and dimensions that are seen as common. Poly was made possible by architects and engineers working together to push the limits of properties in familiar materials such as glass and aluminum to create unfamiliar configurations and designs. Processes like cold bending and hot slumping of glass, stretch forming of aluminum, and the use of new composites result in spectacular designs.
While in pursuit of iconic design, architects and engineers must also grapple with practical considerations of forward-thinking and innovative design: in the case of cold bending of glass, the ASTM standards for long-term tensile strength of sealants and the long-term serviceability of the glass is just starting to catch up, giving architects standards and tests to use in the further development of the use of glass within our buildings.
The Sum of its Parts
Aristotle said that “the whole is greater than the sum of its parts.” This holds true in iconic architecture. The use of highly efficient structures as a compliment or partner to the architecture creates a design greater than the simple sum of its parts. On Poly, we spent countless hours on the interaction between the architecture’s exterior envelope and how it engages the equally expressive and highly efficient structural system. Sure, there are the complications of typical issues such as waterproofing and thermal performance, but due to its shape and the connections at the “nodal” points, a simple flat aluminum cladding would not suffice.
Similar to how cold bending produces a doubly curved glass surface, we needed to find a process that would warp an aluminum panel in similar fashion. We had to figure out how to cover the connection of four straight lines of the structural diagrid, intersecting from unique angles wrapping a modified ellipse. In short, there were no straight lines or flat planes that would enclose this shape. In brief discussions with Boeing and other aluminum experts, we learned of a process of stretch-forming that was utilized by Jangho Curtain Wall Co. Ltd. in China. This involves a process of pulling an aluminum plate with over 300 tons of force to place the aluminum in an elastic state, then pulling it down over a wooden form. Once the aluminum takes the shape of the form, the plate is released and is again structurally stable. There are six unique stretched formed nodal covers on Poly, repeating across the façade.
Another unique material that can take on many complex forms is FRP or fiber reinforced polymers. The Northern California-based Kreysler and Assoc. is trailblazing the use of composites in architecture. This composite material known as FRP, is comprised of different combinations of fiber, and polymer bonding materials to achieve unprecedented freedom in form making and material replication.
Here in Boston, Arrowstreet’s adaptive reuse of Congress Square downtown utilized FRP for a soffit that overhangs historic Congress Street overlooking Post Office Square. Currently under construction, this will be the first project in Boston to use exterior grade FRP. The FRP soffit creates an ephemeral form of ripples to highlight the new glass addition, six and a half stories high, that will sit on top of an existing early 1900s building.
In today’s world of quick deadlines and constant pressure to finish early, it has become increasingly imperative to find and collaborate early with material fabricators that are at the forefront of innovation. This collaboration allows for the pursuit of the next award winning iconic design, and for a study of new uses, modifications or fabrication methods of materials that may lead to new avenues of architecture.
Brian Cook, AIA, is a senior associate at Arrowstreet.