The Hyatt Regency Walkway Collapse Introduction: The Hyatt Regency Hotel was built in Kansas City in 1978. A state of the art building with a 40 story hotel tower and conference facilities. These two components were connected by an open atrium which was 15 metres high. Within this atrium there were three suspended walkways connected the hotel and conference facilities. In July 1981 approximately 2000 people were gathered in the lobby to watch a dance contest. A large crack was heard and the second and fourth floor walkways collapsed onto the lobby. This was the worst structural disaster in American history claiming the lives of 114 people and leaving a further 200 injured. Figure 1. The Proposed Design: Gillum-Colaco International (GCE) was hired to design all structural engineering components of the building including the walkways. The original design was to have the walkway supported by two wide flange beams, one on each side. This was then hung from a box beam. Each box beam was supported by a washer and nut which was threaded onto the supporting rod. This type of connection had virtually no moment so the connection was modelled as a hinge. Figure 2. The Actual Design: Due to a dispute between GCE and Havens, who were the contractors hired to fabricate and erect the atrium steel, the design was changed from Fig 2 to Fig 3. This was a double hanger rod connection to the box beam. The change in design was implemented because Havens did not want to have to thread the entire rod in order to fit the washer and nut. Each support rod of the fourth floor walkway was attached to the atriums cross beams and threaded as shown in Fig 3. The second rod was 100mm away and supported the second floor walkway. Figure 3. Failure: The design failed because of the addition of an extra supporting rod. The extra rod increased the load on the fourth floor nut from 90 kN to 181 kN. The box beams were longitudinally welded as had originally been proposed. Because of this they could not hold the weight of the two walkways. During the collapse, the box beam split and the support rods pulled through them resulting in the fourth and second level walkways falling to the ground level. Who’s Responsible? The major problem with the Hyatt Regency disaster was a lack of clear communication between GCE and Havens. This was particularly prevalent in the drawings that were prepared by GCE. Havens understood these to be final drawings and used them to create the components of the walkways. These were actually only preliminary sketches. Another large error was the fact that there was no final review of the design by GCE which would have allowed them to notice the extra loading on the rods. Figure 4. As a result of these errors all the GCE engineers who signed off on the walkway design lost their engineering licences in the states of Texas and Missouri. GCE also lost the right to be an engineering firm. Conclusions: An engineer has a responsibility to their company and more importantly to the public to ensure that they take all reasonable steps to ensure their design is sound. In the case of the Hyatt Regency walkway collapse the engineers did not undertake a sufficient review of the design of the rod/ box beam connection and this led to a large loss of life. As a result of this case engineers became fully responsible for design projects in the US due to the adoption of a report on the matter by the American Society of Civil Engineering. This case highlights the need to review thoroughly all design modifications during the construction phase of any project. Disasters such as are a reminder of how an error in judgement can lead to catastrophe. Group 3: Ian Thompson Laura Devane David Martin Stephen Conlon