Source: https://www.fireengineering.com, July 17, 2018
By: Gregory Haval
and their effects on emergency incident outcomes. “Complacency” was defined as “satisfaction with a perception of a situation that is not based on reality.” “Hubris” was defined as “self-confidence beyond the level of competence,” eaning that our perception of our skills and abilities was not based on reality.
Both concepts—especially complacency—can affect the course of an incident years before emergency services are dispatched and as early as the design phase of a building. The collapse of the Hyatt Regency skywalks in Kansas City, Missouri, on July 17, 1981, is an example of this kind of complacency. This was the deadliest structural collapse in U.S. history until the destruction by terrorists of the World Trade Center Twin Towers on 9/11.
The original architectural and engineering plans were prepared in 1977. In late 1978, the structural engineer was contacted by a subcontractor who was preparing shop drawings for the fabrication of the structural steel for the skywalks. The fabricator had been retained by the general contractor. The fabricator then proposed to redesign the system of single suspension rods supporting the second- and fourth-floor skywalks to suspend the fourth-floor skywalk from the roof trusses and to suspend the second-floor skywalk from the fourth-floor skywalk framing. The engineer of record approved the design change without checking the calculations to determine whether there would be changes in the loading of structural elements. The shop drawings were approved by the structural engineer in February 1979.
A technician at the architect’s office noticed and questioned the discrepancy between the shop drawings and the design drawings. He was told by the structural engineer that the designs were essentially the same. The shop drawings were stamped as reviewed for conformance with the design concept and compliance with the contract documents.
Figure 1 shows a drawing of the original design of the suspension rod connections at left and a drawing of the revision to which the skywalks were constructed.
The discrepancy between the original design and the structural system that was installed was not noted by the Kansas City building inspectors, who spent only 18 hours, 21 minutes inspecting the entire project during more than two years of construction.
The Hyatt Regency in Kansas City was not a single building; it was three—a hotel tower with 750 rooms and suites; a conference center with restaurants, conference rooms, and ballrooms; and connecting the two was a 15,000-square-foot atrium with a steel and glass roof 50 feet above the floor. This atrium was spanned by three skywalks connecting the hotel with the conference center: one at the third-floor level and the pair at the second- and fourth-floor levels that shared the suspension rod system.
The Hyatt Regency was completed in July 1980. The atrium became one of the social centers of Kansas City, especially for Friday-evening dances, often for more than 1,500 people.
On July 17, 1981, about 1,600 people were present for music and dancing at 7:00 pm, with hundreds on the dance floor and many more watching from the skywalks. A loud crack was heard as the second-floor skywalk dropped six or eight inches. Moments later, more cracking and screeching sounds were heard as the fourth-floor skywalk sagged, split near the middle, and collapsed onto the dance floor, taking the second-floor skywalk with it.
Photo 2 shows the Hyatt Regency atrium after the collapse, with the third-floor skywalk at left still in place and the openings to which the second- and fourth-floor skywalks had connected.
By 4:30 am on July 18, rescue workers had removed the last living victim from the wreckage. By 7:30 am, the last of the victims was uncovered by debris removal. The final death toll was 114, with more than 200 injured, some of whom were permanently disabled.
In the days following the incident, victims, owners, builders, and designers retained investigators and attorneys. The editors of the Kansas City Star believed that the truth should be made known as soon as possible without waiting for litigation to end. The editors retained Wayne Lischka, a young independent structural engineer, gave him press credentials with two of their reporters and a photographer, and sent him to the Hyatt Regency for a limited media tour a few days later.The group was allowed to view the atrium from the second floor of the restaurant area only. Lischka pointed out what he needed to be photographed, and the photographer used a telephoto lens to show the damaged structural steel and its connections. Observation and photos showed that the suspension rods for the fourth-floor skywalk were intact except for the damage at the lower ends caused by the failure of their connection to the box beams supporting the skywalk.
Wayne Lischka gained access to the original structural plans for the building, compared them to the photographs taken at his direction, and found the design change described above. Because of this design change, the load was doubled on the connections on the box beams supporting the fourth-floor skywalk since it was now supporting its own and the second-floor skywalk’s dead and live loads. Deformation of the box beams (photo 3) at the perforations for the suspension rods indicated that the failure had been gradual and ongoing.
Working with Lischka, the Kansas City Star’s editors assembled a front-page article for the July 21, 1981, evening edition, complete with photographs and copies of the building plans.
Further inspection ordered by City Hall showed the same deformation of the box beams supporting the third-floor skywalk that had not collapsed. This structure was removed since it was found too dangerous to leave in place. In the months following, other investigators, including a team from the National Bureau of Standards (NBS), confirmed and added detail to the conclusions reached by Lischka. As the result of the design change in the skywalks, the skywalks barely had the capacity to support their dead loads and no capacity to support any live load. The skywalks had collapsed while carrying about 1/15 of the live load they should have been designed to carry, according to the Kansas City Building Codes.
This catastrophe ended with a landmark negligence lawsuit between the State of Missouri and GCE International Inc.—the structural engineers for the building project. In a report of more than 440 pages, the judge found GCE International and two of its principle engineers guilty of misconduct, negligence, and unprofessional conduct in the practice of engineering. The State of Missouri revoked the engineering licenses of those involved.
Even though the design changes were discussed twice before construction began, overconfidence in the new design being equivalent to the original design resulted in structures with no safety factor and no live-load capacity. Complacency by the engineers was as much a factor in this tragedy as the misconduct, negligence, and unprofessional conduct cited by the judge in his decision.
This catastrophic incident emphasized and reinforced the need for the repeated review of building and structural plans by the architects and engineers during the design phase of a construction project and by the structural component manufacturers and installing contractors during construction. This system had developed over the previous decades as buildings and their designs became more complex. It works well if complacency does not creep in and if there is enough time in the schedule for the plan reviewers to think as they do their work.
For more information on this tragedy including photos, news media articles, NBS and National Institute of Standards and Technology reports and videos, do an internet search for: “Hyatt Regency Kansas City walkway collapse.”
Also visit the Kansas City Star’s web site www.kansascity.com and search on its home page for “Hyatt Regency hotel collapse 1981.”