August 4, 2011
On July 17, 1981, the Hyatt Regency Hotel in Kansas City was hosting a Friday evening dance party. Above the lobby, two walkways supported dozens of party goers overlooking the festivities. Suddenly the walkways collapsed onto the people celebrating in the lobby, killing 114 people and injuring more than 200.
This was one of America’s most tragic structural failures.
The technical cause for the collapse was quickly determined by Exponent engineers: insufficient load capacity of the box-beam-hanger rod connections. The technical cause was well documented in a report published by NIST and it was widely accepted.
Much more complex were the failures in the design and construction process that led to this deficiency. The debate centered on the roles and responsibilities of the engineer of record, on practices in the steel detailing and fabrication industry, and on how to prevent similar failures in the future. Many of these issues were explored in a special issue of the Journal of Performance of Constructed Facilities, published in May 2000 by the American Society of Civil Engineers. This issue included a candid paper by the engineer of record for the project, who had lost his license as a result, and a paper by an engineer who was directly involved with the design. These papers gave a rare and detailed “behind the scenes” account of the design process, and of the factors that led to the failure. This issue also included a paper titled “Engineering Process Failure—Hyatt Walkway Collapse” by Piotr D. Moncarz, P.E. and Robert K. Taylor, P.E. of Failure Analysis Associates (now Exponent)
The crucial finding from reviewing these papers is that the connection that failed had never been designed. The engineer of record thought that the fabricator’s engineer had performed the detailed design of the connection, the fabricator’s engineer thought that the engineer of record had done it. Neither one had.
As these papers describe, some of the factors that contributed to the failure were:
- A draftsman mistakenly omitted the design force from the connection detail. The absence of a design force led the fabricator to believe that the engineer of record had completely designed the connection.
- It was a “fast-track” project. This delivery method placed added time pressures on both the designers and the contractors
- There were personnel changes in the engineer’s and fabricator’s detailing team , which resulted in a lack of continuity.
- The fabricator outsourced partially completed details to an outside detailer, who assumed that the connection had been designed by either the engineer of record or by the fabricator’s engineer.
Obviously, these factors could exist on any project, and they should not compromise the safety of the project. So what has changed in the past 30 years to help make structural design safer?
Although these are good steps in the right direction, more processes can be undertaken.
One aspect of the design process that is sometimes overlooked is the need for structural engineering firms to have an adequate quality assurance and quality control (QA/QC) program, and to follow it. Although no formal studies exist, it is likely that many structural engineering firms, particularly those involved with private projects, may not have a formal QA/QC program. Or, if they do, that it may not adequate or is not followed consistently. If a strong internal QA/QC program had been implemented at the Hyatt Regency project, it would have detected the error that the draftsperson had made, and it would have ensured that all of the connections were designed by an engineer.
Peer reviews are also effective tools for reducing failures. They encourage the collection and organization of the design calculations and documents, they allow a review by a “fresh set of eyes,” and they provide a valuable pause from what can be a hectic design environment. To help facilitate the adoption of peer review legislation by additional states and municipalities, structural engineering societies could prepare and disseminate a model regulation.
Taking these steps will lead to safer structures.