Anyone who has been in an earthquake appreciates the life-saving protection of a steel-framed building. With the Pin-Fuse Joint, Skidmore, Owings & Merrill’s San Francisco office has devised a way for steel structures to ride out a quake that not only keeps the inhabitants secure, but preserves the integrity of the building structure when the aftershocks wear off.
With typical steel construction, beams are welded to columns in perpendicular moment connections, creating a strong grid that will keep a building stable. But during a major seismic event, when moment connections are subjected to too much force, they can crack or permanently malform in a way that cannot be corrected, and the building must be demolished or undergo extensive and expensive repair work.
The Pin-Fuse Joint is installed on the horizontal members at the moment connection; it consists of a circular-plated end connection with slip-critical friction bolts connecting the curved steel end plates. A steel pin in the center of the horizontal beam provides a rotation point. Under normal circumstances, movement from occupants or lateral forces from wind will not move the connection because it cannot overcome the friction of the end plates. But during a seismic event, when the forces reach a critical point, the joint pivots, allowing the steel frame to roll or jolt with the motion of the quake. When the shaking is done, the frame finds its natural center and slips back into place, as though nothing happened.
The jury was taken with the joint both as an object and as a concept. “I thought this was very clever, and beautiful too,” John Ronan said. “It’s the kind of thing you would want to expose.” And for Los Angeles–based Craig Hodgetts, the project hit close to home. “I think it’s a terrific thing. That deformation is a huge problem in the San Francisco area and in L.A. to a lesser extent—and this does address it from an engineering point of view.” What the jury did worry about, however, was the price point, which was not explicitly stated in the submission. “It looks really expensive,” Hodgetts said. “But there might be a way to streamline this design and make it affordable at some point.”
Engineers Skidmore, Owings & Merrill, San Francisco—Mark Sarkisian (structural engineering director); Shea Bond, Jean-Pierre Chakar, Rupa Garai, Eric Long, Neville Mathias, Jun Racines (structural team members); Stanford University, Stanford, Calif.—Gregory Deierlein (collaborating team member)