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  • 6/2/2025
Transcript
00:00July 17, 1981. It's a warm summer evening in Kansas City.
00:05Inside the Hyatt Regency Hotel, the air is filled with the sound of music, laughter, and conversation.
00:12The hotel's grand atrium is alive with energy.
00:15Hundreds of guests have gathered for the hotel's popular tea dance,
00:19a social event that brings people together each week.
00:23On the lobby floor, couples dance to the music.
00:25Above them, guests lean against the railings of the suspended walkways,
00:31looking down at the dancers below.
00:33The walkways themselves are striking, elegant, modern, seemingly integrated into the hotel's architecture.
00:40They create a sense of openness, allowing guests to observe the event from multiple levels
00:43while still feeling connected to the energy below.
00:47The night continues. The crowd sways to the music.
00:51Conversations carry across the vast atrium.
00:53Then, 7.05 p.m., a deep metallic snap cuts through the air.
01:00For a split second, everything is still.
01:03Then, without warning, one walkway collapses onto the one below.
01:07In an instant, both plummet into the crowded lobby.
01:11A deafening impact echoes through the atrium.
01:14The force of the collapse tears through the structure,
01:17sending shattered concrete, twisted steel, and broken glass crashing to the ground.
01:22People standing directly below have no time to realize it.
01:26The sheer weight of the falling structure crushes everything beneath it.
01:31Dust and debris fill the air, muffling the screams of those trapped in the wreckage.
01:36In just moments, the atrium, once a place of music and celebration,
01:41have turned into a scene of devastation.
01:43Survivors stumble through the dust, disoriented.
01:47First responders rush in, pulling people from beneath the rubble.
01:51But what exactly caused this disaster?
01:54In this video, we'll break down the engineering behind these walkways,
01:58analyze the fatal design flaw,
02:00and reveal how a single small modification led to catastrophic failure.
02:04Within minutes of the collapse, emergency responders arrive at the Hyatt Regency Hotel.
02:17First responders, hotel staff, and bystanders rush to search for survivors,
02:22pulling people from beneath the rubble.
02:25The scene is chaotic.
02:27Smoke and dust linger in the air.
02:29Steel beams and shattered concrete block every path.
02:32The collapse leaves 114 people dead and 216 injured,
02:38making it one of the deadliest structure failures in U.S. history.
02:43As rescue efforts continue, investigators arrive at the scene
02:46and begin gathering accounts from those present.
02:49Witnesses describe a sudden, violent drop with no warning,
02:53followed by a sharp metallic snap
02:55and a deafening crash of concrete and steel striking the lobby floor.
02:59While these accounts confirm what occurred,
03:02they do not yet reveal why it happened.
03:05By examining the wreckage,
03:07they begin analyzing their remaining support structures,
03:10searching for signs of material fatigue or construction errors.
03:14To understand why the walkways failed,
03:17we first need to examine how they were originally designed and constructed.
03:20The hotel's atrium was its defining feature.
03:23An open four-story space spanned by three suspended walkways on the second, third, and fourth floors.
03:30These elevated walkways provided access between the upper levels while preserving an open view of the atrium below.
03:37The second and fourth floor walkways were aligned directly above one another,
03:42while the third floor walkway was offset to the side.
03:46Each walkway measured approximately 2.7 meters wide and 36.5 meters long, weighing around 30 metric tons.
03:53The walkways were supported by three cross beams,
03:57which were box girders formed by welding 200-millimeter wide C-channel strips together lengthwise,
04:03creating a hollow core.
04:05Designed to support both their own weight and the live load of guests,
04:08the walkways appeared to float above the atrium floor.
04:11Each of these walkways was suspended using three pairs of 32-millimeter diameter steel hanger rods,
04:18which extended upward and were anchored to the ceiling structure.
04:22The entire system relied on these rods to transfer the walkway loads to the ceiling.
04:27These rods were inserted through holes at the top of each end of the cross beams
04:31and secured at the bottom with a nut.
04:34A washer was positioned between the nut and the beam,
04:37helping to distribute the load evenly.
04:39In the original engineering design,
04:42a single continuous pair of rods was anchored to the ceiling structure
04:46and intended to pass through the cross beams of both the second floor and the fourth floor walkways,
04:52with a nut in the middle of the rods holding the fourth floor walkway
04:55and a nut at the bottom holding the second floor walkway.
04:59However, the fabricator of the rods objected that the entire length of rods below the fourth floor
05:04would have to be threaded in order to screw on the nuts
05:07to hold the fourth floor walkway in place.
05:10There was a concern that the threads would be damaged as the fourth floor structure was hoisted into place.
05:16To simplify installation, a minor change was proposed,
05:20one that would have devastating consequences.
05:22Instead of using a single continuous rod, the final design used two separate sets of rods.
05:28The first set would suspend the fourth floor walkway from the ceiling,
05:32while the second set would suspend the second floor walkway from the fourth floor walkway.
05:37In the original design, the load from each walkway was intended to be independently transferred to the hanger rods.
05:43Each set of cross beams supported only one walkway, meaning one could be lifted without affecting the other.
05:51However, even in the original design, the walkway structure was barely capable of supporting the expected loads
05:57and would not have met the Kansas City building code requirements.
06:01In the new design, the entire weight of the second floor walkway was transferred to the cross beams of the fourth floor walkway.
06:09As a result, if you lift the fourth floor walkway, the second floor walkway moves with it.
06:15While the total load on the hanger rods remained the same at the top,
06:19the nuts on the upper rods now supported the combined weight of both walkways,
06:23effectively doubling the load on the cross-beam-to-rod connection,
06:27a load that far exceeded its structural capacity.
06:31Due to a series of miscommunications between the fabricator and the engineering firm responsible for the walkway design,
06:37the fabricator implemented the new design under the assumption that it was structurally sound.
06:42As later investigations determined, the connection that failed was never designed.
06:47No engineering analysis was performed to ensure its strength.
06:50In 1980, the Hyatt Regency Hotel opened its doors with this fatal flaw embedded in its structure.
06:58For months, the walkways bore the weight of guests without noticeable issues,
07:03but the forces acting on the lower connections were quietly accumulating.
07:07The fourth floor box beam, subjected to excessive stress, began to weaken,
07:12aggravating the strain on the welded connections.
07:14At exactly 7.05 p.m., one side of a box beam on the fourth floor walkway split open along the well,
07:23causing the nut and washer on the hanger rod to split through and break free.
07:28As the first connection failed, the sudden redistribution of weight overloaded the remaining connections.
07:34Within moments, they gave away in rapid succession.
07:37The fourth floor walkway failed catastrophically, plunging directly onto the second floor walkway beneath it.
07:44Overloaded by the sudden impact, the lower walkway could not withstand the force,
07:49and both structures crashed into the densely crowded lobby below.
07:54The Hyatt Regency walkway collapse serves as a tragic reminder of the critical importance of clear communication,
08:01thorough oversight, and ethical responsibility in engineering.
08:04The failure to properly review and assess design changes led to one of the deadliest structural failures in U.S. history.
08:13The Missouri Licensing Board filed a complaint against the engineering firm and two of its engineers,
08:18responsible for the structural oversight of the walkway design.
08:22They were found guilty of gross negligence, misconduct, and unprofessional conduct,
08:27resulting in the revocation of their engineering licenses in Missouri and Texas,
08:31while the firm lost its certificate of authority.
08:35However, despite these professional consequences, they were acquitted of all criminal charges.
08:41Civil lawsuits later led to substantial settlements for the victims and their families.
08:46The lesson of the Hyatt Regency collapse is clear.
08:49Engineering mistakes have real consequences.
08:52And those consequences can be measured not just in numbers, but in lives lost.
08:56It's time to announce the winner from our last video, the Coliseum Poster Giveaway.
09:02Congratulations, and thank you for your comment.
09:05For this video's giveaway, we're offering a brand new poster featuring a vehicle we explored in our differential video.
09:11To enter, like this video, subscribe, and leave a comment below,
09:15telling us what surprised you the most about the Hyatt Regency walkway collapse.
09:18We'll announce the winner in our next upload.
09:21And if you'd like to grab a copy right now and support the channel,
09:24the link is in the description and pinned comment.
09:27And as always, a huge thank you to all of our Patreon and YouTube membership supporters.
09:31Your support helps us keep telling stories like this one.
09:34Until next time, stay curious.