The collapse of the walkway in the Hyatt was not caused by the failure of an expansion joint. The collapse occurs due to a change made by the designer engineers in how one how the walkways were suspended from the roof above.

The original design called for each two walkways to be support by its own set of support rods to roof. Instead the lower walkway was suspended from the structural framing of the upper walkway. The support rod suffered a slip failure and pulled through thea upper walkway framing. The framing of the upper walkway was never designed to carry the weight of the lower walkway.

At the time of the collapse a dance party was underway and walkways were heavily loaded with folks. This heavy live load along with their "swinging" to the music is also believed to have contributed to the failure, although the connection was doomed to fail at some point due to its' basic inadequate design.

NIST has an excellent report on this failure analysis, including pictures of the failed connection.

James G. Munger, PhD, FIFireE, CFPS
www.qdotengineering.com
W3NFA