On the evening of July 17, 1981, some 1,600 people were gathered in the soaring atrium lobby of the new Hyatt Regency hotel in Kansas City for a popular tea dance, many of them watching from two suspended walkways that crossed the lobby overhead. At 7:05 p.m. the fourth-floor walkway tore loose from its supports and crashed down onto the second-floor walkway directly beneath it, and both fell together into the crowd. One hundred and fourteen people were killed and 216 injured — at the time, the deadliest structural collapse in United States history.
The walkways were hung from the atrium roof on steel hanger rods. As designed, a single set of continuous rods was to run from the roof framing down through the fourth-floor walkway and on to the second-floor walkway below, so that each walkway’s weight hung from the rods independently. During fabrication, the steel fabricator proposed a change to two shorter, offset sets of rods — one set from the roof to the fourth floor, another from the fourth floor down to the second. The change looked trivial but was not: it doubled the load carried by the fourth-floor walkway’s box-beam connections, which now had to support the weight of both walkways. The project’s structural engineers approved the fabricator’s shop drawings showing the change without checking it, and the connections were left with barely enough capacity to carry the walkways themselves.
The National Bureau of Standards concluded that the most probable cause of the collapse was the insufficient load capacity of the box beam–hanger rod connections: under the weight of the people on the walkways that evening, the rods pulled through the fourth-floor box beams, each made of two steel channels welded together that split apart under the load. The Bureau also found that even the original, unchanged design would have met only about sixty percent of the capacity the Kansas City building code required.
The collapse became a landmark in professional accountability. Missouri’s licensing board revoked the licenses of the two engineers of record and their firm for gross negligence, incompetence and misconduct, and some $140 million was paid out in settlements. The case — a fatal design change passed through a routine shop-drawing review that nobody checked — is now the standard case study in engineering ethics, taught to underline the engineer’s duty to review design changes and to hold the safety of the public above every other obligation.
Download the NBS Investigation Report — NBSIR 82-2465 (19.4 MB file)