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TIMESTAMPS

    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 2 ^nd floor walkway, directly below the 4 ^th floor walkway, was suspended from the beams of the 4 ^th floor walkway, while the 3 ^rd and 4 ^th 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 2 ^nd and 4 ^th 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).

    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 4 ^th floor walkway to fail. Because of lack of redundancy, this failure caused the collapse of both of the walkways.

    Originally, the 2 ^nd and 4 ^th 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).

ASCE Code of Ethics

Failure in Design

The Hyatt Regency Walkway Collapse

Simpson, Gumpertz & Heger

What Happened at the Hyatt?

Engineering Ethics

Dr. Lee Lowery’s Pictures

Negligence and the Professional "Debate" Over Responsibility For Design

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, C onstruction Failure (1997), 2 ^nd 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), Wh y Buildings Fall Down: How Structures Fail . W. W. Norton, New York, N.Y.

Lowery, Lee, Fourth Floor Beam . [Online Image] Available http://lowery.tamu.edu/ethics/ethics/hyatt/hyatt2.htm , July 1,1999.

Lowery, Lee, Hanger Rod, Washer, and Supporting Nut. [Online Image] Available http://lowery.tamu.edu/ethics/ethics/hyatt/hyatt2.htm , July 1,1999.

Lowery, Lee, Third Floor Hanger Rod and Crossbeam Assembly. [Online Image] Available http://lowery.tamu.edu/ethics/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.

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Last updated Monday, December 06, 1999 05:21:20 PM