On July 17th, 1981, more than 100 people were killed and another 200 or so injured when two walkways collapsed within the Hyatt Regency Kansas City Hotel. At the time, a Tea Dance was being held in the hotel's lobby when the walkways fell. This was the deadliest structural collapse in U.S. history until the tragic events of the World Trade Centre some 20 years later.

In the following article we'll take a quick look at what happened. A detailed analysis is out of the scope of this article, but if you are interested here is a great source.

Lobby view during the first day of investigation

[Image Source: Dr. Lee Lowery, Jr., P.E./Wikimedia Commons]

Countdown to disaster

The Hyatt Regency Kansas City Hotel began construction in May of 1978. The 40-story building, despite some setbacks and delays, opened its doors to the public in July of 1980. One major setback was the dramatic collapse of the atrium roof when connections failed on the northern end of the building.

The lobby was one of the hotel's defining features and included a multi-story atrium spanned by elevated walkways suspended from the ceiling. The steel, glass and concrete construction walkways connected the second, third and fourth floors from north to south. Each walkway was around 37 meters long and weighing in at around 29,000 kgs. Such was the design, that the fourth level walkway was directly above the second level walkway.

Disaster strikes

At the time of the disaster, 1,600 people gathered for a Tea Dance. At around 7 pm, the second-level walkway had about 40 spectators. The third and fourth-level walkways held about 16 and 20 people on each, respectively.

During construction, an apparent design flaw was identified. Contractors decided to change the design which resulted in the double loading of the connection between the fourth-floor bridge and the atrium roof. Support beams and tie rods had been designed to hold the weight of each walkway and any people standing on it. The new design change, though apparently subtle, was enough to critically undermine the safety of the structures.

The connections spectacularly failed, the fourth-floor and second-floor bridges plunged to the atrium's floor. As the dust settled, piles of steel, concrete, and glass encased many bodies. Rescue teams would later liken the scene to a war zone. It must have been a terrible sight.

Third-floor walkway of the Kansas City Hyatt Regency

[Image Source: Dr. Lee Lowery, Jr., P.E./Wikimedia Commons]

Rescuers arrive on the scene

Rescue teams arrived at the Hyatt Regency Hotel and began a 14-hour rescue operation. The team included members from the Fire Brigade, EMS units and doctors from five local hospitals. What they found was a 60-ton pile of steel, concrete, and glass encased the victims. The hotel's forklift trucks and fire department's powerful jacks were unable to move the debris alone. Local companies were asked to help. Many responded and volunteered manpower as well as hydraulic jacks, acetylene torches, compressors and generators to aid the rescue operations. Truly remarkable.

Large sections of collapsed walkways were so heavy that cranes were needed to move them. Triage centers and morgues were quickly set up on the hotel's drive and lawn to help with the wounded and dead. Without being too graphic, fatally injured victims were given morphine to ease their pain and rescuers were even required, at times, to dismember bodies to reach other victims. Some survivors even had limbs amputated to get them out.

The fallen bridges weren't the only issue. To add insult to injury, damaged sprinkler systems gushed water into the atrium. These systems were supplied from tanks rather than city supplies. Becuase of this, it was not possible the turn them off. Trapped victims now had the very real prospect of being drowned.

Kansas City's fire chief quickly realized the hotel's front doors were acting as a dam for the quickly flooding atrium floor. He ordered a bulldozer to break the doors and connect the broken pipes with a fire hose to prevent further flooding. To prevent fires power supplies had to be cut. Large amounts of airborne dust severely limited visibility for the rescue teams.

[Image Source: Wikimedia Commons]

How could this have happened?

Three days after the disaster and rescue operation, Wayne G. Lischka, a structural engineer, began conducting a thorough investigation. He quickly discovered that the tie rod designs were to blame. Lischka found a serious departure from the original design. Walkways were meant to be suspended from the atrium on continuous rods. At some point, this had been changed, a critical error.

The manufacturer of these rods had concerns at the time. In their opinion, the need for the tie rods to be threaded along their entire length meant they could easily be damaged during walkway hoisting. Ultimately rendering them useless. They changed the design to include two sets of tie rods to be used instead of the intended continuous ones. One set was now to connect the fourth floor to atrium roof. The other for the second-floor walkway attachment to the fourth-floor walkway.

This was to prove fatal. This required the fourth-floor beams to support both the fourth-floor walkway but also the underlying second-floor walkway's dead weight. A recipe for disaster. That night the stress became too great. The box beams split along welds and the nuts supporting them slipped through the gap.

The investigation also found that design changes, poor communication, poor or no calculations and general negligence all contributed to the collapse. Unbelievably, at times, design changes were confirmed over the phone rather than checking the documentation or calculations. Shocking!



The final word

The fallout was pretty serious. Responsible engineers and firms had their licenses revoked, some even went bankrupt. Compensation claims from the courts awarded victims around $140 Million dollars not to mention insurance payouts. This disaster remains a classic model for engineering models, ethics, and errors not to mention disaster management.

This should never have happened. Although plans had been changed, the original designs were far from perfect. According to the investigation, it would only have met 60% of the City's prescribed building code requirements. Suffice to say that gross negligence on the part of team members led to a disaster that could have easily have been avoided. A real tragedy.

The Hotel has since undergone various renovations and refurbishments. Directly after the disaster, a single walkway was re-installed but this time supported by columns. Other than the third floor now being left without a connecting walkway, the lobby generally retains its original design. The Hyatt Regency Hotel is now known as the Sheraton at Crown Centre.

Sources: Engineering, ThinkReliability

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