April 23, 2015
Dr. Troy Morgan, Mr. David Peraza, and co-author recently published, "Collapse of Crossed Pendulum Ceiling Systems Due to Unstable Equilibrium."
A failure analysis was conducted following the collapse of a 13,000 lbs., 165 ft by 16 ft rectangular steel suspended ceiling panel structure in a large public space. The ceiling framing structure was suspended from the roof structure with a unique system of stainless steel cables that cross one another between the ceiling structure attachment points and the anchorage to the supporting slab above. During construction, the entire ceiling panel structure rotated out of its installed horizontal position when the temporary cable bracing was removed, causing one edge of the ceiling structure to drop suddenly and the opposite edge to lift. No failure of the suspension cables or their attachments occurred.
The collapse was caused by a design error that did not properly consider the stability of the suspended ceiling panel. The behavior of this particular ceiling panel structure is generalized to a wider class of crossed pendulum structures, and stability conditions based purely on system geometry are found using energy principles for a wide set of feasible parameters. Guidance is provided for the design of suspended systems involving crossed hangers, such as ceiling structures, bridges, and suspended walkways.