Hyatt Regency walkway collapse

The Hyatt Regency hotel walkway collapse happened on July 17, 1981 during a tea dance at the Hyatt Regency Hotel in Kansas City, Missouri.

The 40-story-tall Hyatt Regency hotel was constructed in 1978. Its lobby had a multistory atrium that was crossed on the second, third and fourth levels by three suspended concrete walkways. On July 17, 1981 approximately 2000 people had gathered in the atrium to participate in and watch a structural engineer hired by the Kansas City Star newspaper, discovered the cause - an unauthorized change in the design of the walkways.

The walkways were suspended from a set of tie rods, with the second floor walkway hanging directly underneath the fourth floor walkway. The original designs by Gillum-Colaco International called for a single set of rods running from the second floor all the way to the ceiling, with the fourth floor walkway supported partway along them by a set of nuts. The rods were manufactured by the Havens Steel Company. Havens Steel disapproved of the Gillum-Colaco design since it was in fact impossible to build as drawn, as it would have required the whole of the rod below the fourth floor to be threaded in order to screw on the nuts to hold the fourth floor walkway in place. These threads would almost certainly have been damaged beyond use when the structure for the fourth floor was hoisted into position. Instead, they went with an alternate plan in which two separate sets of tie rods would be used; one connecting the fourth floor walkway to the ceiling, and the other connecting the second floor walkway to the fourth floor walkway.

In the original design the nuts on the fourth floor walkway only had to support the weight of the fourth floor walkway itself, and were sized according to that requirement. In the revised design, however, the fourth floor nuts were required to support both the fourth floor walkway and the second floor walkway hanging from it. This change in requirements was not noticed, and so the same nuts as in the original design were used - now holding up twice the weight they should have been. When the walkways became heavily loaded, the nuts and washers on the fourth floor walkway pulled through the walkway's support beams and both walkways collapsed.

Investigators concluded that the basic failure that led to this flaw was a lack of proper communication between Gillum-Colaco and Havens Steel. In particular, the drawings prepared by Gillum-Colaco were only preliminary sketches but were interpreted by Havens as finalized drawings. Gillum-Colaco failed to review the final design which would have allowed them to catch the error in increasing the load on the connections. It also turned out that the original design for the hanger rod didn't satisfy the Kansas City building code either, though it still would have withstood the demands placed on it much better than the revised design.

Gillum-Colaco was cleared of criminal negligence, but the the Missouri Board of Architects, Professional Engineers, and Land Surveyors convicted the engineers employed by Gillum-Colaco who had signed off on the final drawings of gross negligence, misconduct, and unprofessional conduct in the practice of engineering. They lost their engineering licenses in the states of Missouri and Texas and their membership to ASCE. Gillum-Colaco lost its licence as an engineering firm, and billions of dollars were awarded to victims and their families in subsequent civil lawsuits.