Professionalism/Jack Gillum and the Hyatt Regency Skywalks

Background
In the mid-1970’s, Kansas City, Missouri was still best known by outsiders for the cattle trade. As part of an urban redevelopment plan to change the city image to a busy, modern, commercial center, a large, luxurious Hyatt Regency Hotel was added to the plans. The hotel was to be a beacon on the skyline as the tallest building in the city. The Hyatt name had gained a reputation of grandeur and extravagance since the 1960’s, so it was the perfect choice to change the image of the city. The signature of the hotel chain was sweeping and open interior spaces. Following that tradition, a glass-enclosed atrium was designed to be the center piece of the Kansas City Regency Hyatt. The expansive interior space was highlighted with three seemingly floating walkways that connected the two sides of the hotel. The fourth floor walkway was directly above the second floor with the third floor independently to the side.

The ground breaking of the hotel occurred in 1978 and Jack D. Gillum and Associates was contracted to take care of the structural engineering of the building. The firm was known for its innovative building design, but this architecturally dramatic building was going to be its biggest challenge yet. The contract that Jack D. Gillum and Associates signed was a fast track design and construct contract, meaning that construction began while the design plans were still being finished.

Disaster struck early in the construction process in October 1979 when a tennis court sized section of the glass atrium roof collapsed. No one was injured in the accident. An in-house and peer review of the incident followed. The same problem was found by both parties: an incompatibility in the steel and concrete interface. The glass roof was repaired and the incident was written off as a one time problem. A further setback occurred in late 1979 when the general contractor went bankrupt. Construction was resumed with new management when Crown Center quickly took over the project. Finally, the new and spectacular Hyatt Regency Hotel opened its doors in July 1980.

Skywalks Collapse
About a year after the opening on Friday, July 17, 1981, the hotel was holding a tea dance in the atrium. At 7:00 pm, a swing dance competition was being held. While the big band played, 2,000 spectators looked on, filling the atrium and walkways to get a better view. The event was much anticipated and people happily sang, drank, and danced. At 7:05 pm, a loud metallic crack stopped the band and dancers in their tracks. Without warning, the fourth floor skyway collapsed on to the second floor skyway immediately below and, with a crash, the entire 32 tons of concrete collided with the atrium floor. Anyone within the vicinity of the walkways was killed or trapped by the falling concrete.

The disaster did not end there. The collapsing concrete of the walkways had punctured the water tanks for the whole hotel. Water then began pumping into the atrium. If there were survivors in the rubble of the walkways, they now faced the risk of drowning. With the quick thinking of the rescue crew, drastic measures were taken and a bulldozer was used to break the door from the outside. Heavy machinery and jack hammers were needed for the rescue effort to gain access to the tons of concrete. The last living victim was excavated from the rubble a full ten hours after the collapse occurred. In total, 114 people were killed and 216 others were injured, making the Hyatt Regency walkway collapse the most deadly structural failure to that point.

Cause of the Collapse
Investigations after the Hyatt disaster revealed the primary cause of the walkway collapse: a significant design change in the steel beams attaching the walkways to the ceiling. Jack D. Gillum and Associates initially designed the walkways with a single steel rod attaching the second floor walkway to the fourth floor walkway and then to the ceiling. The drawing below shows the initial design on the left. However, Gillum’s design was modified significantly during construction. Havens Steel, the steel fabricator for the project, decided to change the design to use a double hanger rod box beam, shown in the right side of the image. This design would be easier to build, as it would not require threading the entire rod. Although easier to construct, the new design doubled the load on the rod connection on the fourth floor walkway box beam. While Havens Steel reportedly “checked” this design with Gillum and Associates in a phone call and made the modification on their shop drawings, the design was never submitted for approval or tested. Havens Steel built the new rods according to the shop drawings and the American Institute of Steel Construction (AISC) guidelines, assuming the design was structurally sound. Jack Gillum later commented that “the connection that failed was never designed”, because no engineering analysis was performed to ensure the strength of the connection.

The new double rod design proved itself insufficient when the walkways collapsed. The load of the concrete used in the walkways and weight of the people standing on them was too great for the rod connections. The box beams effectively collapsed, so that the walkways slipped off the rods. The image to the right illustrates the colossal failure of the rod connections. The fourth floor walkway connections failed first, resulting in the large popping noise heard by the crowds at the dance. The second floor walkways followed almost instantaneously. The box beams had most likely been weakening and distorting during the year that the hotel had been open, but the added stress of the tea dance spectators caused the connections’ total failure.

It is important to note that even the initial connection designed by Gillum and Associates was under-engineered. The single rod design would only hold sixty-percent of the load required by AISC and Kansas City building codes. Therefore, when the design was modified and the load on the connections doubled, the connections could only hold thirty percent of the required load. Thus, the new rod connection was severely flawed.

Although the failure of the steel rods supporting the walkways was responsible for their collapse, it was not the only design problem with the Hyatt. The atrium roof collapsed during construction due to deficiencies in the concrete and steel interface. Gillum also later noted that changes were made to the screen wall design during construction. The horizontal supporting splices were removed for architectural reasons, a change also only made in the shop drawings.

Swiss Cheese Model
Marc Gerstein, in his book “Flirting with Disaster,” uses the Swiss Cheese model to help explain the Hyatt walkway failures. The layers of protection against failures have holes, and when all the holes line up disaster occurs. Gerstein claims that while poor structural engineering was the primary cause of the walkway failure, “it was the job of the engineering company to create a process that trapped slips, engineering errors, and oversights” Investigations into the causes of the collapse revealed several of the holes in the engineering company's design process that allowed such a poorly constructed series of skywalks to be built.

Investigations
After the tragedy, a public investigation was launched by the Natural Bureau of Standards to determine the cause of the collapse. At the same time, the Kansas City Star hired a structural engineer, Wayne Lischka, to investigate privately as an undercover reporter. Lischka took photos of the wreckage and from an examination of these photos, determined that the welded box beams holding the rods were what had failed. Lischka went to City Hall and requested the blue prints for the building, only to find that the plans submitted to City Hall did not match what was actually built. The Kansas City Star published these findings asserting that it was the welded box beams that led to the failure of the walkways. The NBS investigation eventually came to the same conclusion. They recreated the welded box beams in their laboratory and applied a force that was estimated to be equal to the force of the walkways and the people that were standing on them during the collapse. They found that the beams were not able to withstand a sufficient amount of force. The NBS report noted:

The hanger rod detail actually used in the construction of the second and fourth floor walkways is a departure from the detail shown on the contract drawings. In the original arrangement each hanger rod was to be continuous from the second floor walkway to the hanger rod bracket attached to the atrium roof framing. The design load to be transferred to each hanger rod at the second floor walkway would have been 20.3 kips (90 kN). An essentially identical load would have been transferred to each hanger rod at the fourth floor walkway. Thus the design load acting on the upper portion of a continuous hanger rod would have been twice that acting on the lower portion, but the required design load for the box beam hanger rod connections would have been the same for both walkways (20.3 kips (90 kN)).

Aftermath
After the investigations, the Missouri Board of Architects, Professional Engineers, and Land Surveyors filed a complaint against Daniel Duncan, Jack Gillum, and G.C.E. International Inc., charging gross negligence, incompetence, misconduct, and unprofessional conduct in connection with the walkway collapse. During the trial that took place, evidence was presented that showed that G.C.E. did not adequately test the design of the walkways or fully investigate after the atrium collapse. G.C.E. was found responsible for the change from 1 rod to 2 rods, and it was found that, even if Havens did not specifically note the change in the beam design, G.C.E. was still responsible for the final design check.

Gillum, Duncan, and G.C.E. were found guilty of gross negligence, misconduct, and unprofessional conduct in November, 1984. Duncan and Gillum lost their licenses to practice engineering in the states of Missouri and Texas. G.C.E. had its certificate of authority as an engineering firm revoked.

The American Society of Civil Engineering issued a report in response to the tragedy. This report stated that the Engineer of Record has responsibility and authority for all aspects of the structural design. Kansas City, Missouri also overhauled their building codes, requiring that all load calculations be done by a city-appointed engineer.