Building Collapse Cases/Hyatt Regency Walkway
Hyatt Regency Walkway Collapse
On July 17, 1981, a pair of walkways in the Hyatt Regency Hotel in Kansas City collapsed, killing 114 people and injuring over 200. Two walkways were stacked on top of each other and suspended from the ceiling; the top walkway fell on the bottom walkway, and the two fell onto the floor of the crowded atrium.
Among the relevant facts of the case were:
- The hanger detail for the two walkways, as originally designed, could not be built. The steel fabricator requested a change in the detail, and the engineer of record approved it, without checking the calculations.
- Examination of the box beams supporting the upper walkway after the collapse showed that the upper hanger rod had pulled through the beam. The beam was made of two steel channels welded together (Levy and Salvadori, 1992, Kaminetzky, 1991, Rubin and Banick, 1987, Feld and Carper, 1997). The instructor may have to explain the structural behavior of these details.
- Although many people were on the walkway when it collapsed, the actual load was still much less than the code mandated capacity for the system (Levy and Salvadori, 1992).
However, recent papers by Gillum, Luth, Moncarz and Taylor, and Pfatteicher (2000) have shown that the story is much more complicated than the brief discussion above indicates, and should be consulted for a more complete understanding.
- Gillum, J. D. (2000), The Engineer of Record and Design Responsibility, ASCE Journal of Performance of Constructed Facilities, May 2000, Vol. 14, No. 2
- Luth, G. P. (2000), Chronology and Context of the Hyatt Regency Collapse, ASCE Journal of Performance of Constructed Facilities, May 2000, Vol. 14, No. 2 (note: winner of the 2001 Best Paper Award for this journal)
- Moncarz, P. D., and Taylor, R. K. (2000), Engineering Process Failure – Hyatt Walkway Collapse, ASCE Journal of Performance of Constructed Facilities, May 2000, Vol. 14, No. 2
- Pfatteicher, S. K. A. (2000), “The Hyatt Horror:” Failure and Responsibility in American Engineering, ASCE Journal of Performance of Constructed Facilities, May 2000, Vol. 14, No. 2
- Roddis, W. M. K. (1993). “Structural Failures and Engineering Ethics,” J. Struct. Engrg., ASCE, 119(5), 1539-1555.
- Rubin, R. A., and Banick, L. A., “The Hyatt Regency Decision: One View,” pp. 161-167, ASCE Journal of the Performance of Constructed Facilities, August 1987.
- Shepherd and Frost, 1995, p. 75
- Wearne, 2000, Chapter 4 - "No Time to Scream: The Hyatt Regency"
Rachel Martin's Case Study - originally developed for the UAB REU Site, 1999
Kansas City, Missouri
July 17, 1981
Design and Construction
In July of 1980, the Hyatt Regency opened to the public after four years of design and construction. A 40-story tower, an atrium, and a function block, housing all of the hotel’s services, combined to form this impressive building. Three walkways suspended from the atrium’s ceiling by six 32-mm-diameter tension rods each spanned the 37-m distance between the tower and the function block. The 2nd floor walkway, directly below the 4th floor walkway, was suspended from the beams of the 4th floor walkway, while the 3rd and 4th floor walkways hung from the ceiling (Feld and Carper, 1997).
The erection of this hotel, however, was not as picture perfect as the final product. During construction, the atrium roof collapsed as a result of inadequate movement in the expansion joint and improper installation of a steel-to-steel concrete connection. Concerned about the building’s structural integrity, the owner hired another engineering firm to investigate the collapse and check the roof design. The consulting structural engineering company also rechecked all of the connections and found nothing to cause alarm. Construction resumed and the hotel opened a little less than 2 years later (Roddis, 1993).
On the evening of July 17, 1981, between 1500 and 2000 people inundated the atrium floor and the suspended walkways to see a local radio station’s dance competition (Feld and Carper, 1997). At 7:05, a loud crack echoed throughout the building and the 2nd and 4th floor walkways crashed to the ground killing 114 people and injuring over 200 others. It was the worst structural failure in the history of the United States (Levy and Salvadori, 1992).
Causes of Failure
Upon investigation, the National Bureau of Standards (NBS) discovered that the cause of this collapse was quite simple: the rod hanger pulled through the box beam causing the connection supporting the 4th floor walkway to fail. Because of lack of redundancy, this failure caused the collapse of both of the walkways.
Originally, the 2nd and 4th floor walkways were to be suspended from the same rod (as shown in fig-1) and held in place by nuts. The preliminary design sketches contained a note specifying a strength of 413 MPa for the hanger rods which was omitted on the final structural drawings. Following the general notes in the absence of a specification on the drawing, the contractor used hanger rods with only 248 MPa of strength. This original design, however, was highly impractical because it called for a nut 6.1 meters up the hanger rod and did not use sleeve nuts. The contractor modified this detail to use 2 hanger rods instead of one (as shown in fig-2) and the engineer approved the design change without checking it. This design change doubled the stress exerted on the nut under the fourth floor beam. Now this nut supported the weight of 2 walkways instead of just one (Roddis, 1993).
Analysis of these two details revealed that the original design of the rod hanger connection would have supported 90 kN, only 60% of the 151 kN required by the Kansas City building code. Even if the details had not been modified the rod hanger connection would have violated building standards. As-built, however, the connection only supported 30% of the minimum load which explains why the walkways collapsed well below maximum load (Feld and Carper, 1997).
While Kansas City did not convict the Hyatt Regency engineers of criminal negligence due to lack of evidence, the Missouri Board of Architects, Professional Engineers, and Land Surveyors was not as timid. It convicted the engineer of record and the project engineer of gross negligence, misconduct, and unprofessional conduct in the practice of engineering. Both of their Missouri professional engineering licenses were revoked, and they lost membership to ASCE. Also the billions of dollars in damages awarded in civil cases brought by the victims and their families dwarfed the half million dollar cost of the building (Roddis, 1993).
Neither the original nor the as-built design for the hanger rod satisfied the Kansas City building code making the connection failure inevitable. If, however, the building design had contained more redundancy this failure may not have resulted in the complete collapse of the walkway. Kaminetzky (1991) suggests two much stronger design alternatives for the connectors. The toe-to-toe channels used in the Hyatt Regency provided for weak welding which allowed the nut to pull through the channel/box beam assembly initiating the collapse. A back-to-back channel design using web stiffeners when necessary (fig-3) or the use of bearing crossplates in conjunction with the toe-to-toe channels (fig-4) would have made the connection much stronger making it much more difficult for the nut to pull through (Kaminetzky, 1991).
The Hyatt Regency walkway collapse highlighted the lack of established procedures for design changes as well as the confusion over who is responsible for the integrity of shop details (Roddis, 1993). The legal repercussions experienced by the Hyatt engineers established the engineer of record's responsibility for the structural integrity of the entire building including the shop details. It is important for all parties to fully understand and accept their responsibilities in each project (Feld and Carper, 1992). Certain procedural changes could help prevent similar collapses.
- The engineer of record should design and detail all nonstandard connections.
- All new designs should be thoroughly checked.
- All of the contractor's modifications to design details should require written approval from the engineer of record (Kaminetzky, 1991).
During the trial the detailer, architect, fabricator, and technician all testified that during construction they had contacted the project engineer regarding the structural integrity of the connection detail. Each time he assured them that the connection was sound claiming to have checked the detail when in reality he had never performed any calculations for this design at all. Neglecting to check the safety and load capacity of a crucial hanger even once shows his complete disregard for the public welfare (Rubin and Banick, 1987). Ethical engineers should check and recheck their work in order to be able to properly assure the public of a building's structural integrity (Delatte, 1997). Also, the high number of fatalities resulting from the walkway's collapse raises the questions of whether the factor of safety required for a building should be proportional to the possible consequences of it collapse (Kaminetzky, 1991).
- Delatte, Norbert (1997). "Failure Case Studies and Ethics in Engineering Mechanics Courses." Journal of Professional Issues in Engineering Education and Practice, July 1997.
- Feld, Jacob and Carper, Kenneth, Construction Failure (1997), 2nd Ed., John Wiley & Sons, New York, N.Y.
- Kaminetzky, Dov, Design and Construction Failures: Lessons from Forensic Investigations (1991). McGraw-Hill, New York, N.Y.
- Levy, Matthys and Salvadori, Mario (1992), Why Buildings Fall Down: How Structures Fail. W. W. Norton, New York, N.Y.
- Lowery, Lee, Fourth Floor Beam. [Online Image] Available http://ethics.tamu.edu/ethics/hyatt/hyatt2.htm, July 1,1999.
- Lowery, Lee, Hanger Rod, Washer, and Supporting Nut. [Online Image] Available http://ethics.tamu.edu/ethics/hyatt/hyatt2.htm, July 1,1999.
- Lowery, Lee, Third Floor Hanger Rod and Crossbeam Assembly. [Online Image] Available http://ethics.tamu.edu/ethics/hyatt/hyatt2.htm, July 1,1999.
- Roddis, W.M. (1993). "Structural Failures and Engineering Ethics." Journal of Structural Engineering, May 1993.
- Rubin, Robert and Lisa Banick (1987). "The Hyatt Regency Decision: One View." Journal of Performance of Constructed Facilities, August 1987.
- Ruins of Hyatt Regency Walkway. [Online Image] Available http://www.sgh.com/kchyatt.htm, July 1, 1999.
Illustrations from Chapter 2 of the book Beyond Failure: Forensic Case Studies for Civil Engineers, Delatte, Norbert J., ASCE Press.