On July 17th, 1981, 114 people were killed and at least another 216 were 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 non-deliberate structural collapse in U.S. history and the deadliest structural collapse until the tragic events of the World Trade Center some 20 years later.
Here, 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 to know more, here is a great source.
Countdown to the Hyatt Regency collapse disaster
The Hyatt Regency Kansas City Hotel began construction in May of 1978. Despite some setbacks and delays, the 40-story building 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 (121.4 feet) long and weighed in at around 29,000 kgs (63,934 lbs). Such was the design, that the fourth level walkway was directly above the second level walkway.
Disaster strikes at the Hyatt Regency Kansas City Hotel
At the time of the disaster, around 1,600 people were 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 each.
But what actually caused the Hyatt Regency walkway collapse?
During construction, an apparent design flaw was identified. The original plan called for six steel hanger rods to run directly from the second-floor walkway to the ceiling for support. However, the steel manufacturing contractor objected to this design, as it required rods to be screw-threaded to hold the fourth-floor walkway in place.
The contractor identified this as a potential hazard and proposed a new plan: a set of tie rods that connected the fourth-floor walkway to the ceiling, and a separate set that connected the second-floor walkway to the fourth-floor walkway.
The plan was ultimately used for construction, meaning the second-floor walkway support was connected to the fourth-floor walkway. This meant that the upper hanger rods of the fourth-floor walkway took on the undue strain, as they had to hold double the load initially intended. The design change, though seemingly subtle, was enough to critically undermine the safety of the structures.
In short, the tie rods connect the walkways together. As a result of changes in the tie rod design, the rods carried more weight/stress than they were supposed to. And as a result of this, undue stress was placed on the beam, which subsequently split. So, in the end, it was both the rods and the beam that were carrying extra weight and had undue stress.
The connections spectacularly failed, and the fourth-floor and second-floor bridges plunged to the floor of the crowded atrium below. As the dust settled, piles of steel, concrete, and glass encased many bodies. Rescue teams would later liken the scene to a war zone.
Rescuers arrive on the scene of the civil engineering disaster
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 encasing 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 so they could be extracted from the rubble.
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. Because of this, it was not possible to turn them off. Trapped victims now faced the very real prospect of being drowned.
Kansas City's fire chief 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.
How could this deadly civil engineering project happen?
Three days after the disaster and rescue operation, Wayne G. Lischka, a structural engineer, began conducting a thorough investigation. He eventually 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 used to connect the fourth floor to the atrium roof. The other attached the second-floor walkway to the fourth-floor walkway.
This design was to prove fatal. This required the fourth-floor beams to support both weight of boh the fourth-floor walkway and also the underlying second-floor walkway. As it turned out, 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 in some cases, 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, to say the least.
The aftermath of the Hyatt Regency walkway collapse
The fallout was pretty serious. Engineers and firms that were found responsible had their licenses revoked, some even went bankrupt. Compensation claims from the courts awarded victims around $140 million dollars, and there were also large insurance payouts.
Most experts came to the conclusion that 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 percent 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 Center.
The Hyatt Regency walkway collapse remains one of the worst civil engineering disasters in US history. It has been widely studied and remains a warning to all current and future engineers of the potential cost of cutting corners and not being thorough.
The Hyatt Regency disaster remains a model for engineering ethics, not to mention disaster management, hopefully never to be repeated again.
Note: This article has been updated to make it clear that both the rods and the beam were carrying extra weight and had undue stress.