On July 17, 1981, two overhead walkways in the Hyatt Regency Hotel in Kansas City, Missouri, collapsed, killing 114 people and injuring 216. Loaded with partygoers, the concrete and glass platforms crashed onto a tea dance in the lobby. The collapse resulted in billions of dollars of insurance claims, legal investigations, and city government reforms.
The hotel had been built just a few years before, during a nationwide pattern of fast-tracked large construction with reduced oversight and major failures. Its roof had partially collapsed during construction, and the ill-conceived skywalk design progressively degraded due to a miscommunication loop of corporate neglect and irresponsibility. An investigation concluded that it would have failed under one-third of the weight it held that night. Convicted of gross negligence, misconduct and unprofessional conduct, the engineering company lost its national affiliation and all engineering licenses in four states, but was acquitted of criminal charges. Company owner and engineer of record Jack D. Gillum eventually claimed full responsibility for the collapse and its unchecked design flaws, and he became an engineering disaster lecturer.
The disaster contributed many lessons and reforms to engineering ethics and safety, and to emergency management. It was the deadliest non-deliberate structural failure since the collapse of Pemberton Mill over 120 years earlier, and remained the second deadliest structural collapse in the United States until the collapse of the World Trade Center towers 20 years later.
The Kansas City Star described the national climate of the late 1970s as "high unemployment, inflation and double-digit interest rates [that added] pressure on builders to win contracts and complete projects swiftly". Described by the newspaper as fast-tracked, construction began in May 1978 on the 40-storey Hyatt Regency Kansas City. There were numerous delays and setbacks, including the collapse of 2,700 square feet (250 m2) of the roof. The newspaper observed that "Notable structures around the country were failing at an alarming rate", which included the 1979 Kemper Arena roof collapse and the 1978 Hartford Civic Center roof collapse. The hotel officially opened on July 1, 1980.
The hotel's lobby was its defining feature, with a multi-storey atrium spanned by elevated walkways suspended from the ceiling. These steel, glass and concrete crossings connected the second, third and fourth floors between the north and south wings. The walkways were about 120 feet (37 m) long and weighed about 64,000 pounds (29,000 kg). The fourth-level walkway was directly above the second-level walkway.
Hyatt Regency hotels in business districts had taken to hosting Friday after-work tea dances in their soaring atrium areas. About 1,600 people gathered in the Kansas City hotel's atrium for such a dance on the evening of Friday, July 17, 1981. The second-level walkway held about 40 people at about 7:05 p.m., with more on the third and an additional 16 to 20 on the fourth. The fourth-floor bridge was suspended directly over the second-floor bridge, with the third-floor walkway offset several yards from the others. Guests heard popping noises and a loud crack moments before the fourth-floor walkway dropped several inches, paused, then fell completely onto the second-floor walkway. Both walkways then fell to the crowded lobby floor. A diner at the 42nd-floor revolving restaurant atop the Hyatt said it felt like an explosion.
The rescue operation lasted 14 hours, directed by Kansas City emergency medical director Joseph Waeckerle. Survivors were buried beneath the walkways' many tons of steel, concrete and glass, which the fire department's jacks could not move. Volunteers responded to an appeal and brought jacks, flashlights, compressors, jackhammers, concrete saws and generators from construction companies and suppliers. They also brought cranes and forced the booms through the lobby windows to lift debris. Deputy Fire Chief Arnett Williams recalled this immediate outpouring from the industrial community: "They said 'take what you want'. I don't know if all those people got their equipment back. But no one has ever asked for an accounting and no one has ever submitted a bill."
The dead were taken to a ground-floor exhibition area as a makeshift morgue, and the hotel's driveway and lawn were used as a triage area. Able survivors were instructed to leave the hotel to simplify the rescue effort, and morphine was given to the mortally injured. Blood centers quickly received lineups of hundreds of donors. The Life Line helicopter pilot compared the carnage to the Vietnam War but in greater numbers.
Visibility was poor because of dust and because the power had been cut to prevent fires. Water from the hotel's ruptured sprinkler system flooded the lobby and put trapped survivors at risk of drowning. The final rescued victim, Mark Williams, spent more than nine hours pinned underneath the lower skywalk with both legs dislocated and having nearly drowned before the water was shut off.
A total of 114 were killed and 216 injured, 29 of whom were rescued from the rubble. Rescuers often had to dismember bodies to reach survivors among the wreckage. A surgeon spent 20 minutes amputating one victim's pinned and unsalvageable leg with a chainsaw; that victim later died.
The Kansas City Star hired architectural engineer Wayne G. Lischka and national engineering firm Simpson, Gumpertz, and Heger Inc. to investigate the collapse, and Lischka discovered a change to the original design of the walkways. Within days, a laboratory at Lehigh University began testing box beams on behalf of the steel fabrication source. The Missouri licensing board, the state attorney general and Jackson County investigated the collapse over the following years. Edward Pfrang, lead investigator for the National Bureau of Standards, characterized the neglectful corporate culture surrounding the entire Hyatt construction project as "everyone wanting to walk away from responsibility". The NBS's final report cited structural overload resulting from design flaws where "the walkways had only minimal capacity to resist their own weight". Pfrang concluded they would have failed with one-third of the occupants' weight.
Investigators found that the collapse was the result of changes to the design of the walkway's steel hanger rods. The two walkways were suspended from a set of 1.25-inch-diameter (32 mm) steel hanger rods, with the second-floor walkway hanging directly under the fourth-floor walkway. The fourth-floor walkway platform was supported on three cross-beams suspended by the steel rods retained by nuts. The cross-beams were box girders made from 8-inch-wide (200 mm) C-channel strips welded together lengthwise, with a hollow space between them. The original design by Jack D. Gillum and Associates specified three pairs of rods running from the second-floor walkway to the ceiling, passing through the beams of the fourth-floor walkway, with a nut at the middle of each tie rod tightened up to the bottom of the fourth-floor walkway, and a nut at the bottom of each tie rod tightened up to the bottom of the second-floor walkway. This original design supported 60% of the minimum load required by Kansas City building codes.
Havens Steel Company had manufactured the rods, and the company noted that the whole rod below the fourth floor would have to be threaded in order to screw on the nuts to hold the fourth-floor walkway in place. These threads would be subject to damage as the fourth-floor structure was hoisted into place. Havens Steel proposed that two separate and offset sets of rods be used: the first set suspending the fourth-floor walkway from the ceiling, and the second set suspending the second-floor walkway from the fourth-floor walkway.
This design change would be fatal. In the original design, the beams of the fourth-floor walkway had to support the weight of the fourth-floor walkway, with the weight of the second-floor walkway supported completely by the rods. In the revised design, however, the fourth-floor beams supported both the fourth- and second-floor walkways, but were only strong enough for 30% of that load.