Southern California‘s enviable climate and landscape—sunny skies, balmy temperatures, picturesque mountains, and surfer-friendly beaches—come at a geological cost: proximity to active earthquake faults.
Local AEC industry professionals are adept at meeting detailed building code requirements for structural safety. But when it comes to cutting-edge facade systems, said KPFF principals Mark Hershberg and Nathan Ingraffea, designers and builders are left with little to go on.
Hershberg and Ingraffea will dig into this and other challenges and opportunities associated with seismic design at this month’s Facades+ LA conference in a panel on “Anchors & Approvals: Structure and Skin in Seismic Design.” In addition to Ingraffea (Hershberg will moderate), panelists include Dana Nelson (Smith-Emery) and Diana Navarro (California OSHPD).Seismic events have plagued Southern California throughout history. (Orange County Archives / Flickr)
“A tremendous amount of time has been spent to increase the safety of building structures in seismic events through continual updates of the code, but very little work has been done to understand the behavior of facade systems in seismic events,” noted Ingraffea. “This is a shame since the value of the facade system could be just as high as the value of the structure itself, and failure of either one could be catastrophic. This is a great opportunity for someone who wants to invest the time to modernize the code.”
In the meantime, designers, engineers, fabricators, and builders are left without “a well thought out design standard for seismic design of facade systems,” said Ingraffea. The ASCE 7 contains only half a page on the topic. Worse still, the relevant text is “on one hand, very basic (one equation to check) and on the other hand overly onerous (dynamic racking tests), and they really do not apply to many modern facade systems,” he said. As a result, building envelope design teams must tackle the issue of seismic design on a case-by case basis. “‘Industry standard’ is a term you hear a lot when you do a lot of facade engineering but from what I’ve seen the [seismic design] ‘standard’ is all over the board,'” said Ingraffea.
In practical terms, a lack of data or guidance on seismic activity and building skins can cost precious time and money. “Most of the challenges we see with facade design in seismic hot spots are due to the amount of movement that can occur in a building system during a seismic event,” explained Hershberg. “We service many clients who want to use new facade concepts or products that may have been developed overseas, and many times the products haven’t been tested to determine the range of seismic movement that they can accommodate.” The design team is thus forced to perform a series of qualification tests. “This introduces an additional set of schedule risks that are sometimes overlooked,” said Hershberg.