When people enter a building, an unwritten agreement is made: the structure they’re entering is stable, secure, and safe.

While this implicit agreement is almost always honored, rare tragedies remind us that mistakes during building construction can have deadly consequences. Tragedy can strike high dollar, well-intentioned projects — as was the case with the Missouri Hyatt Regency.

The collapse of the two Hyatt Hotel walkways in 1981, which resulted in over a hundred dead, is the second deadliest structural collapse in US history — surpassed only by 9/11. What exactly caused this structural collapse, and what could’ve been done to prevent it? Take a look at this video to learn more.

To understand the answer to these critical questions, we need to look back at the history of the building itself.

About the Hyatt Regency Kansas City

Construction on Hyatt Regency Kansas City began in the late 1970’s. This 45-story, Missouri hotel was once the city’s tallest building, measuring in at 504 ft.

The defining feature of the hotel was the lobby atrium consisting of three overhead walkways. These crossings connected the north and south wings for the second, third and fourth floors.

In 1981, two of these walkways collapsed during a hotel event in which 1,600 people were in attendance. This disaster killed 114 and injured 214 people. To this day, the Hyatt Regency walkway collapse remains a sobering example of industry negligence and a constant reminder of why accuracy in design and prefabrication is crucial.

So, how did the unthinkable come to fruition, and what construction oversights led to this tragedy?

What went wrong with the Hyatt?

The cause of the incident can be traced all the way back to the design process — specifically a fatal change the steel manufacturer made to the original walkway design plan.

The original plan, designed by Jack D. Gillum and Associates, 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. The plan required rods be screw threaded to hold the fourth floor walkway in place, and the contractor identified this as potential material hazard that could cause threading damage.

Havens Steel Company 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.

In the revised design plan, which was ultimately used for construction, the second floor walkway support was connected to the fourth floor walkway and therefore the upper hanger rods of the fourth floor walkway took on undue strain.

What designers didn’t realize at the time –– and what investigators discovered after the fact –– is that this configuration effectively doubled the load of the fourth floor walkway since it took on the load of the walkway below it.

Investigators found that the tie rods connecting the fourth floor walkway to the ceiling could barely hold the dead load off the fourth floor walkway alone — much less the added weight of spectators. As a result, the fourth floor walkway fell onto the second floor walkway, and then both structures fell to the crowded lobby below.

Aftermath

One of the greatest errors made in the construction of the Hyatt Regency walkways was miscommunication. A lack of collaboration between the construction company and the steel contractors lead to faulty prefabrication, unstable design, and an overall shoddy structure.

For example, preliminary sketches by Jack D. Gillum and Associates were wrongfully perceived by Havens Steel Company contractors to be finalized. Moreover, structure instability could have been identified, and remedied, through basic review and simple calculation from either party involved.

As a result of vast-reaching culpability, the construction company, steel contractor, and hotel owner paid victims and their families $151 million in settlements, judgements, and class action lawsuits.

Of course, the worst consequence of all was the significant loss of life. Due to simple design oversights, many people were put in harm’s way unnecessarily. This accident stands as a testament to the disastrous consequences of negligence within construction projects.

If one thing can be learned from this tragedy, it’s that every stage of a construction project has a significant effect on safety. From prefabrication, to erection, negligence at any project stage can have dire consequences. This disaster has changed engineering and has even been used as a case study for students across the globe.