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1,500 people gather for a dance in the Hyatt Regency Hotel in Kansas City. The second and 4th floor skywalks, hung from steel rods, fail. They collapse and crush 114 people to death.
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00:00The luxury Hyatt Regency Hotel in Kansas City. It's just one year old and is famed for its ambitious architectural
00:08design.
00:09One sultry July evening, almost 1500 people crowd inside the hotel's hallmark atrium for a tea dance.
00:19Suddenly, part of the building collapses, killing 114 people. It's the worst structural failure in U.S. history.
00:27Now, using advanced computer simulation, we reveal what caused the Kansas City Hyatt collapse.
00:36Disasters don't just happen. They're a chain of critical events. Unravel the clues and count down those final seconds from
00:46disaster.
00:52The American Midwest. Missouri. Kansas City.
01:011978. To many outsiders, it's still a Midwestern backwater, best known for cattle trading.
01:09In reality, the city is emerging from the shadow of economic recession as a diverse commercial center.
01:15Kansas City authorities greenlight a major urban redevelopment scheme.
01:21A new $50 million luxury hotel, the Hyatt Regency.
01:27The project looks set to shake off the city's outdated cow town image.
01:36May 1978. Builders start work on the 150-meter tall, 40-story Hyatt.
01:43As they begin phase one of the build, local engineering firm GCE, owned by Jack Gillum, is still finalizing the
01:51hotel's design.
01:53This new, fast-track approach means the project should be completed much more swiftly than a conventional build.
02:01Gillum has a ten-year track record of innovative building projects.
02:05But the Hyatt Corporation expects a groundbreaking architectural statement.
02:11Turning the vision into a reality will be one of his firm's biggest challenges yet.
02:19The hotel centerpiece will be its impressive 44-meter-wide, 15-meter-high, glass-ceilinged atrium.
02:28Three suspended walkways will span this vast space, connecting guest rooms to a conference center and shopping complex.
02:37But then, 17 months in, there's a major setback.
02:43A section of the atrium's glass ceiling, the size of a tennis court, crashes to the ground.
02:52Engineer Jack Gillum analyzes the problem.
02:54He discovers that bolts connecting ceiling panels to the steel roof beams were wrongly installed.
03:00But he concludes that the accident is a one-off.
03:07July 1, 1980.
03:10Despite the setbacks, the Kansas City Hyatt Regency Hotel opens on schedule.
03:18It's one of the city's most spectacular buildings.
03:21And the atrium's suspended walkways quickly become a major talking point.
03:27Your first impression was this large, open, airy space, and these skywalks seemingly suspended in air.
03:33And people went, wow.
03:36Friday, July 17th, 1981.
03:416 p.m.
03:47In the 12 months since it opened, the Hyatt has become one of the city's top night spots.
03:53Tonight, 1,500 people crowd into the famous atrium for one of the hotel's most popular regular events.
04:02A 1940-style tea dance competition.
04:06As the dancers practice their moves, a TV crew arrives in the lobby.
04:11Reporter Michael Mahoney has worked for the local news station KMBC for a year.
04:15He's here to film a light-hearted feature item for the evening news.
04:19But it's not his idea of a major assignment.
04:23I hate features. I like hard news stories.
04:26And I took the job in Kansas City as an opportunity to get into a large American market.
04:31And hopefully at some point I would work my way into what I was more comfortable with, which was a
04:36hard news story.
04:38On the other side of the lobby, engineer Walter Trueblood and his wife Shirley are enjoying their eighth tea dance
04:45at the Hyatt.
04:46They've shared a passion for dancing since they were teenage sweethearts courting in the 50s.
04:51As loyal customers, Walter and Shirley enjoy special benefits.
04:56The tea dance people had been kind enough to send us two free drink tickets, and I never turned down
05:01a free martini in my life.
05:07Local mortgage broker Frank Freeman is a first-timer at the tea dance.
05:12He's here with his boyfriend of five years, Roger Grigsby.
05:17They've been looking forward to the dance for weeks, and Roger is in his element.
05:23He was an extrovert. There wasn't anybody he didn't know.
05:28He could talk to anybody, and you'd think he had known him for life, and he had just met him.
05:33Meanwhile, Walter and Shirley Trueblood decide against entering the competition.
05:39Instead, they join dozens of other couples crowding onto the first-floor walkway,
05:43which offers a bird's-eye view of the dance floor five meters below.
05:507.04 p.m.
05:55The band strikes up a popular foxtrot, and the dance competition begins.
06:08Mike Mahoney's crew films a top shot from the first-floor restaurant.
06:12On the first-floor skywalk, Walter and Shirley Trueblood sway to the music, booming up from the atrium.
06:19Nine meters above them, dozens more watch from the third-floor skywalk.
06:25On the lobby floor, directly underneath the skywalks, Frank Freeman and Roger Grigsby admire the competitors' moves.
06:387.05 p.m.
06:41In the restaurant on the first-floor mezzanine, reporter Mike Mahoney's cameraman runs out of power.
06:47At that point, Dave was setting up his shot, and I reached over into our camera bag to get some
06:54fresh batteries.
06:56Then, Mahoney hears a noise from across the atrium.
07:02I heard this real sharp metallic pop, pop, and it was a sound that was so foreign to the environment
07:08that I immediately looked up.
07:11There was a loud pop, and the floor dropped about six to eight inches.
07:16I took Shirley's arm and said, I think we ought to step off.
07:19We took about three steps.
07:22Mike Mahoney traces the popping noise to the skywalks opposite him.
07:27I was directly on level with the second walkway.
07:30The second walkway began to sag, and it took just a few seconds, but it seemed like forever at the
07:36moment.
07:36It sort of sagged down, and then all of a sudden, it just dropped.
07:41People watch in horror as the first and third-floor glass and concrete skywalks plummet into the crowded lobby.
07:49The upper level came down, and the whole thing went down as an elevator.
07:54You looked at that and went, oh, my God.
07:58Dozens of dancers and spectators lie dead, crushed beneath 65 tons of concrete and steel.
08:04Hundreds more are buried alive.
08:06Unless rescuers reach them fast, many more will die.
08:15Moments ago, local reporter Mike Mahoney was capturing these carefree images of a tea dance in Kansas City.
08:23Now his video camera records these horrific scenes of devastation.
08:30It was an awful scene.
08:31It was just terrible.
08:33There were people that were cut badly.
08:35There were people that were mutilated.
08:36There were people that had had limbs amputated.
08:39And there were people that had been trapped underneath these walkways,
08:43either smashed to the ground or sandwiched in between.
08:47And so it was a gruesome scene.
08:50Stunned survivors make frantic 911 calls.
08:54They need ambulances at the Hyatt region.
08:56Part of the lobby fell in on a whole bunch of people.
09:00Do you know how many injuries there are?
09:01There must be a hundred.
09:037.07 p.m.
09:09Two minutes since the collapse.
09:12Mortgage lender Frank Freeman is in shock.
09:14He and his boyfriend Roger were standing beneath the walkways when they collapsed.
09:19Frank has been hit on the back and shoulder by falling debris,
09:22but escaped being crushed by the narrowest of margins.
09:26When it was all said and done, I was facing the catwalks
09:29and the toes of my shoes were just barely touching the catwalks on the floor.
09:37There's no sign of Roger.
09:46A few meters away, lying under the remains of the first and third floor walkways,
09:51is property valuer Mark Williams.
09:53Just seconds ago, he was getting a drink at the bar.
09:57Now he's pinned to the floor under 65 tons of wreckage.
10:04My left leg was up behind my head and up here behind my right ear.
10:11My right leg was torn out of the socket and was also laying back up here behind me.
10:18So both of the legs are bent behind me and are up behind my head.
10:27Now engineer Walter Trueblood, who was on the first floor skywalk,
10:30regains his senses.
10:32There's a crushing weight on his chest.
10:36The only thing I could move was my arm enough to pull my tie off,
10:41so it would give me a little more air.
10:44He has no idea where his wife Shirley is, or even if she survived.
10:56717.
10:59Firefighters and emergency personnel arrive.
11:01They swiftly set up a makeshift morgue in the hotel lobby.
11:09Outside, they turn the hotel's taxi rank into a treatment center.
11:16In his concrete tomb, Walter Trueblood has no idea if his wife Shirley is alive.
11:25Then, he hears something.
11:29The next voice I heard was good old Shirley saying,
11:32Walt, and I asked her how she was doing.
11:38I remember Walter was calling me and wanting to know, you know, if I was alright.
11:44And we couldn't touch, but we could talk.
11:51Now, broken water pipes severed by the collapse pose a new threat to survivors.
11:58Water from the hotel's giant tanks is flooding the lobby at a rate of over 1,000 liters per minute.
12:06Under the rubble, hundreds of people who survived the collapse now face the prospect of drowning.
12:16Mark Williams can feel the water rising.
12:22I'm starting to breathe the water into my nose.
12:26And I remember thinking to myself, I'm on one of the highest points in the city of Kansas City, and
12:31I'm going to drown to death.
12:33As Mark struggles to keep his head above water, rescuers are helpless to stem the flow.
12:44Kansas City's fire chief pinpoints the problem.
12:47The hotel's front doors are acting like a dam, stopping the water in the lobby from escaping.
12:55He sends in bulldozers.
12:58They smash the doors down.
13:03Water starts to pour out of the lobby.
13:10To mark Williams' huge relief, the water levels start to fall.
13:189.30.
13:23Over two hours since the collapse,
13:26Walter and Shirley Trueblood finally hear rescue workers nearby and shout for help.
13:32The rescue workers attach steel cables to the beam pinning Shirley to the floor
13:38and begin to lift it with a crane.
13:41They have to go slowly.
13:43One slip and the beam could kill her.
13:48They had been talking with us.
13:51And I told them, I said, I feel like I'm about to faint.
13:55Would that be bad?
13:56And I remember him saying, old lady, please hang on.
14:00He said, I'm almost there.
14:04At last, rescuers pull Shirley free.
14:11Just meters away, another team drags her husband Walter from the rubble, screaming in agony.
14:1810 p.m.
14:22Frank Freeman, who was finally persuaded to leave the hotel,
14:25is getting treatment at a nearby medical center when a call comes in.
14:35Rescuers have found the body of a man.
14:38He fits Roger's description.
14:41They bring Frank a photo to make sure.
14:46And he didn't look.
14:54He didn't look like he'd been hit with anything.
14:57I mean, he had no cuts.
15:00There are no bruises.
15:01It looks like he was just laying there sleeping.
15:05And I said, what happened?
15:07And he said, he had a broken neck.
15:142.30 a.m.
15:19Seven and a half hours after the collapse,
15:22now rescuers are only finding dead bodies.
15:28What they don't realize is that under the rubble, someone is still alive.
15:35But property valuer Mark Williams is buried so deep
15:38that he can't even hear the workmen above him.
15:43I'm getting mad.
15:44You know, why isn't somebody lifting this stuff off me?
15:47I'd be organizing a group of people to lift this off of me.
15:51Then he hears something.
15:55Rescuers are drilling into the debris directly above him.
15:59I heard someone bang on something above my head,
16:05be it the sky walk or whatever.
16:07And I started yelling, hey, I'm under here.
16:11But the noise of the jackhammers drowns out Mark's frantic cries.
16:17He's survived the walkway collapse and the threat of drowning.
16:20Now Mark Williams faces the unthinkable, serious injury or even death
16:25at the hands of the rescue workers.
16:28The jackhammer comes through the rubble again and it goes between my legs.
16:35And now I'm thinking, they've triangulated me.
16:38The next one's coming right through the middle of my back.
16:40And I got braced for it.
16:45Help!
16:48Then as the crew line up the jackhammer for another run,
16:51somebody finally hears Mark's desperate cries.
16:54Help! Somebody!
16:56And I remember a guy saying, my God, there's somebody alive under here.
17:044.30 a.m.
17:12Firefighter Ray Wynn pulls Mark Williams from the pile of debris.
17:19Almost ten hours after the collapse, he's the last person found alive.
17:23But he's horribly injured.
17:25You could see the soles of his shoes back here.
17:30And he sits up and I'm like, wow, this guy's alive.
17:39I was happy, happy as hell, to see him.
17:495 a.m.
17:52An ambulance crew rushes Mark to hospital.
17:55He's still conscious, but his back is broken and his kidneys are failing.
18:02I do remember laying there and my mother asked the doctor,
18:08is he going to live?
18:09And the doctor said, I don't think he's going to make it.
18:13I sat up and I said, like hell, I'm not going to make it.
18:17I'm going to be hunting ducks on October 27th when the season opens.
18:23The news, a special report.
18:26As Mark Williams undergoes emergency surgery, the enormity of the Hyatt tragedy emerges.
18:32Who is responsible for the Hyatt skywalk collapse?
18:34Because of the Hyatt disaster, Missouri state officials say...
18:37The tragedy lingers on in the lives of the survivors and the loved ones of the dead.
18:43114 people have been killed.
18:46A further 186 are injured.
18:50Many of them severely.
18:54It's the deadliest structural failure in American engineering history.
19:00Across the United States, people want answers.
19:04How can a key part of a prestigious public project like the Hyatt Hotel simply fall apart?
19:10Now, by rewinding the disaster and by going deep into the investigation, we reveal what really happened at the Kansas
19:18City Hyatt.
19:19How so many people died.
19:21And why the hotel's state-of-the-art skywalks gave way with such devastating consequences.
19:27Advanced computer simulation will take us where no camera can go.
19:32Into the heart of the disaster zone.
19:40Monday, July 20th, 1981.
19:45Three days after the disaster, relatives hold the first funerals for the victims.
19:54Kansas City is in mourning.
20:05Hyatt, the hotel operator, and the building's owner, the Crown Center Redevelopment Corporation, start their own investigations into the tragedy.
20:17But Kansas City's mayor, Richard Berkeley, wants an independent public inquiry.
20:23He asks the National Bureau of Standards to step in.
20:29The NBS is a highly regarded independent federal body that provides scientific analysis for the U.S. government.
20:36But its investigation could take months.
20:43Local newspaper, the Kansas City Star, decides to shortcut the process.
20:48The paper wants a local structural engineer, Wayne Lischke, to become its undercover investigator.
20:54I was surprised by the phone call and a little apprehensive about taking the job.
21:01On one side I wanted to do it because I wanted to get involved and see what really did happen.
21:11Lischke knows that the Hyatt was a fast-track project completed in just under two and a half years.
21:17Did the speed of the construction cause shoddy workmanship?
21:21Or did faulty materials, defective steel or poorly mixed concrete, cause the collapse?
21:27If so, many more buildings under construction in booming Kansas City may be at risk.
21:37The answers lie in the rubble inside the Hyatt's atrium.
21:44Three days after the collapse, the building's owners decide to let the press inside the ruined atrium.
21:53But the reporters, among them undercover sleuth Wayne Lischke, soon find there's a catch.
22:03The journalists are only allowed to view the wreckage from 30 meters away.
22:10But the Kansas City star guessed that Lischke might be kept at arm's length and hatched an ingenious plot.
22:18Lischke is armed with a secret weapon.
22:20A photographer with a telephoto lens.
22:27Lischke can see the tangled wreckage of the first and third floor walkways where they fell on the lobby floor.
22:35Overhead, all that remains of the original structure are six, five meter long hanger rods, still fixed to the ceiling.
22:42It's enough to allow Lischke to work out the walkway design.
22:47The upper walkway would have been suspended from the ceiling by this set of rods.
22:53Lischke realizes that there must have been a second set of rods bolted into the upper walkway that carried the
22:59lower walkway, nine meters below.
23:03More importantly, the ceiling hanger rods are a crucial clue to where the failure happened.
23:11The first thing that caught my eye was the rods were still hanging from the ceiling.
23:19Since the rods are intact, Lischke believes that the structure must have failed at the point where the upper walkway
23:25was connected to the hanger rods.
23:29Did a faulty fixing at this critical connection point fail?
23:33To find out, he would need to examine the wreckage more closely.
23:37Something the builders' owners will not allow.
23:42Lischke hopes the photographs may reveal more, but now he has a brainwave.
23:47City Hall must hold a set of the hired blueprints.
23:50They'll detail the fixings used and may hold some clue to their apparent failure.
23:57But City Hall tells Lischke he can't see the blueprints.
24:02Librarians are in the process of cataloguing them.
24:05His undercover investigation for the Kansas City Star hits a brick wall.
24:16While Lischke's sleuthing stalls, the official investigation gets into gear.
24:23A team of four scientists from the National Bureau of Standards flies into Kansas City.
24:28Among them is lead investigator Edward Frank.
24:32His first priority, to examine the Hyatt's collapsed walkways.
24:37But when he arrives at the Hyatt, Frank and his MBS team are shocked and baffled by what they find.
24:49The lobby is empty.
24:51The wreckage of the walkways and the crucial evidence it contains have disappeared.
25:01Scientists flown in from the National Bureau of Standards, or MBS, to investigate the Hyatt Regency Skywalk collapse have hit
25:08a problem.
25:08The walkway wreckage has gone.
25:11The building's owners have taken it away for private analysis.
25:15For lead investigator Dr. Edward Frank, Chief of the Bureau's Structures Division, it's a massive flood.
25:21Of course, as you know, the debris has been moved. We have not had a chance to see that.
25:25We were shocked to have it removed, and very disappointed.
25:33Frank immediately petitions the circuit court of Jackson County for access to the wreckage which lies in a warehouse downtown.
25:41If the court denies the MBS request, its independent investigation of the Hyatt disaster is dead in the water.
25:50The MBS team starts to examine eyewitness accounts for clues to the cause of the collapse.
25:56Many say that the Hyatt's walkways were overcrowded that evening.
26:00They were encouraging people to dance in the walkways.
26:04They just said use the entire lobby as a dance floor, which everybody was doing.
26:09Some experts say that people dancing on the walkways may have put them under unforeseen stress.
26:15All of a sudden, areas that were meant for people walking from the elevator to a restaurant became dance floors.
26:21And I think that's absolutely math.
26:25Pat Foley, Hyatt Hotel's president, rebuts the claims that the walkways were overloaded.
26:31The catwalks are designed to hold people shoulder to shoulder, as many as you can jam on there.
26:38NBS investigators examine Kansas City's building codes.
26:42They find the codes require public structures to be capable of carrying a load of 488 kilograms per square meter.
26:51The first and third floor walkways should have been strong enough to carry at least 1,280 people.
26:59But no one knows exactly how many people it held that evening.
27:04Then, NBS investigators get a break.
27:09They learn of news reporter Mike Mahoney's unique footage of the tea dance on the night of the disaster.
27:16Investigators pour over the footage.
27:20They discover that several of Mahoney's shots focus on the famous skywalks.
27:27It's like being given that information on a silver platter.
27:31It was very, very, very useful.
27:34Investigators work out that at the time of the collapse, there were 40 people on the first floor walkway and
27:4023 on the third floor walkway.
27:4263 in total.
27:45They calculate that 63 people would only exert a load of 83 kilograms per square meter, a fraction of the
27:52possible maximum load.
27:56The number of people alone is clearly not enough to overload the walkway.
28:01But could just 63 people still trigger disaster if enough of them were dancing on the walkways?
28:11In 1940, news cameras captured the Tacoma Narrows Bridge, tearing itself apart.
28:18High winds created a violent swaying motion in the structure,
28:23ultimately causing the bridge to collapse.
28:28It's an extreme example of what engineers call harmonic vibration.
28:35Now the NBS asks, could people swaying on the Hyatt walkway have created a similar effect?
28:44Experts know that all structures, however solid, vibrate imperceptibly at their own individual frequency.
28:51If the people on the walkway were moving at the same frequency, it could cause harmonic vibration.
28:57That would set up a wave motion in the walkway that could deform the structure and ultimately cause it to
29:04fail.
29:06To determine if harmonic vibration did cause the collapse,
29:09the NBS team needs to establish the natural frequency of the walkways
29:14and the treading frequency of people they carried.
29:17The tempo at which they were dancing or swaying to the music.
29:25Investigators learned that the band was playing a popular Foxtrot at the time of the collapse.
29:34When they analyze the tune, they discover it has a treading frequency of 1.1 hertz or beats per second.
29:41They compare it to the natural frequency of the surviving identical second floor walkway.
29:49They discover that its natural frequency is 7.1 hertz, more than six times faster.
29:56Since the two frequencies are different, harmonic vibration cannot be a factor in the disaster.
30:04It's a dead end.
30:06The NBS investigation stalls.
30:12Meanwhile, engineer Wayne Lischka's unofficial investigation for the Kansas City Star gets a shot in the arm.
30:21The Hyatt building plans are now back at City Hall after cataloging.
30:27He hopes they might hold some clue to the walkway's collapse.
30:31But what he finds in City Hall comes as a bombshell.
30:39I was shocked at that point in time.
30:42It literally only took seconds to realize that what was on the plans and what was built in the field
30:49were not the same thing.
30:54The design plans, filed by Jack Gilliam's engineering firm, GCE, show the first and third floor walkways hanging from the
31:02ceiling by a series of 14 meter long hanger rods.
31:06But Lischka knows from his visit to the Hyatt that this is not how the walkways were actually built.
31:12The rods still hanging from the ceiling were simply not long enough to reach the lower walkway.
31:20A second set of rods bolted into the upper walkway must have carried its twin below.
31:26He's already deduced that the structure failed at the point where the upper walkway was connected to the ceiling rods.
31:33Now he's beginning to understand why.
31:36According to the plans, this critical connection point was only meant to bear the weight of the upper walkway.
31:43In the built structure, it carries the weight of the lower walkway as well.
31:49Twice its intended load.
31:54Lischka needs to know, did engineer Jack Gilliam change the connection point design to take account of this extra load?
32:05Hours later, the newly developed photographs of the walkway wreckage give him his answer.
32:14They clearly show that several of the upper walkway connection points have dramatically failed.
32:22Three crossbeams form the walkway's basic structure.
32:26At the connection point, the hanger rods pass through the end of each beam or channel and are secured by
32:32a nut underneath.
32:34It's starkly obvious to Lischka why this connection point design was not up to the task.
32:41These are basically two eight inch channels similar to the ones that were used in the skywalk.
32:46Normally, if you wanted to make a walkway out of two channels, what they would have done is turned them
32:52back to back and taken the rod and put it in between.
32:56On the Hyatt, what they did is they took two channels and they turned them toe to toe and then
33:02they welded them to form a box beam.
33:06Welding the two pieces together makes it very weak right through here.
33:14Welded box beams were adequate to provide the walkway's basic framework.
33:19But using them to form the connection point poses a serious problem.
33:24Here, they must bear the entire load of both walkways.
33:27But the nature of their structure transfers these huge forces to the beam's weakest and thinnest points, its walls.
33:35Lischka believes the connection point design was a recipe for disaster.
33:41Putting two channels toe to toe is a ludicrous way to do it.
33:45It was then and is now.
33:50Lischka publishes his findings in the Kansas City Star.
33:56If he's right, then the collapse was not caused by faulty materials, but by bad design.
34:03But without access to the walkways themselves, it remains no more than an intriguing theory.
34:12Then, 12 days after the collapse, the circuit court of Jackson County issues a crucial judgment.
34:18It grants the NBS investigation team access to the remains of the walkways locked up in a Kansas City warehouse.
34:32The investigator's first priority to confirm where the walkways gave way.
34:40Amid the wreckage of the upper walkway, they unearth all six of its critical connection points and make a disturbing
34:47discovery.
34:51On each of them, the welds on the box beam have folded inwards and upwards, allowing the hanger rod to
34:57pull right through.
35:08One box beam, named 9-UE, shows signs of longer term damage than the others, suggesting it gave way first.
35:18It looks as though Lischka was right.
35:21The box beam design of the connection points was the walkway's Achilles heel.
35:27Well, just looking at the box beams, you know, you have to shake your head and say, I sure wouldn't
35:32do it that way.
35:36Both Lischka and Frang think a failure in the box beam connections is the cause of the disaster.
35:41But unlike Lischka, Frang can put the theory to the test.
35:48In the National Engineering Laboratory in Gaithersburg, Maryland, investigators attach steel box beams to hanger rods to make two exact
35:56replicas of the connection point.
35:59They weigh every scrap of walkway debris and calculate that the total load on the connection was 8,150 kilograms,
36:07over eight tons.
36:12First, they want to find out if the critical connection point was able to take the weight of the walkways
36:17without people.
36:22The scientists subject the first replica to a constant eight tons of load.
36:30Four seconds in, there's no change.
36:3620 seconds in, they detect movement.
36:43After 52 seconds, it stops.
36:51Under the weight of walkways alone, the walls of the beam start to bow.
36:55But the connection does not give way.
36:59But investigators know that there were 63 people on the walkways when they fell.
37:05They estimate that this would add an extra ton, bringing the total load to just over nine tons.
37:14They repeat the experiment with a second identical connection.
37:18This time, they'll gradually add the extra weight to observe exactly what happens to the connection points.
37:26At 8,070 kilograms, the side walls distort further, and the base starts to give way.
37:37At 8,160 kilograms, the weld gives way with a crack.
37:46Then, at 8,255 kilograms, it fails completely.
37:54The base of the connection, the point bearing the greatest stress, simply folds like cardboard.
38:00The bolt, attaching the walkway to its hanger rod, rips clean through.
38:07Under a steady mechanically exerted force, the connection actually gives way some 815 kilograms short of the estimated load.
38:19The NBS conclusion is clear cut and deeply shocking.
38:24The third floor walkway connections were nowhere near strong enough to carry the weight of two walkways and people.
38:32In fact, they were so weak, they had just one third of the load capacity required by Kansas City building
38:39codes.
38:40From the day that they were put up, they were a disaster waiting to happen.
38:49The investigation takes 10 months.
38:52It reveals in chilling detail exactly what caused two walkways to tear loose from their supports,
38:58high above a crowded dance floor, leaving 114 Friday night revelers seconds from disaster.
39:097 p.m., 5 minutes to disaster.
39:14The Hyatt's Friday night tea dance buzzes with 1,500 partygoers.
39:19Dozens of people flock onto the third floor walkway to escape the throng.
39:23But beneath their feet, the walkway's six connection points struggle to carry the nine-ton load.
39:31At the walkway's eastern end, the connection point at the end of Boxbeam 9UE has been gradually deforming for 16
39:40months.
39:43Beneath the walkways, people are totally unaware of the danger overhead.
39:497.04 p.m., one minute to disaster.
39:55Shirley and Walter Trueblood join the crowd on the first floor walkway.
40:01Seconds later, the base of Boxbeam 9UE buckles.
40:04As its welds snap, people hear the popping from up to 30 meters away.
40:10As the base of the beam folds, the hanger rod rips free.
40:14As the restraining nut smashes into the top of the beam above with a sharp crack, the walkways jolt down
40:21sharply.
40:22Two seconds later, disaster strikes.
40:26Boxbeam 9UE fails.
40:28The five remaining connections on the third floor instantaneously unzipped.
40:34The third floor walkway plummets down at over 15 meters per second.
40:4065 tons of concrete and steel crashes to the lobby floor in just 1.6 seconds.
40:52A fatal flaw in the construction of the walkways is responsible for the deaths of 114 people.
41:02The job of the MBS team was solely to explain the technical reasons for the collapse.
41:08But the victims of the tragedy still want answers to the wider questions.
41:14How could a public structure be built without anyone realizing it was not up to the job?
41:20And who was to blame for the walkway's fatal flaw?
41:25The full story would emerge in a series of sensational court cases that took place in the wake of the
41:31disaster.
41:32What they revealed would shock America and transform the way buildings are built and designed in the U.S. forever.
41:42Official investigators have revealed that the Kansas City Hyatt Skywalks collapsed because the way they were connected to hanging rods
41:49was fatally flawed.
41:51The critical connection points had just one third of the load capacity required.
41:58The spotlight now falls on Jack Gillam, head of engineering firm GCE, which designed the Hyatt.
42:06In the wake of the collapse, the American Society of Civil Engineers, or ASCE, and the Missouri State Board investigate
42:14Gillam's role.
42:16It emerges that it was the Hyatt architects who requested box beams for the walkways.
42:22Their motives were aesthetic. Box beams are the easiest type of beam to conceal with plasterboard.
42:29But as chief engineer, it was Gillam's job to ensure that all aspects of the walkway were structurally sound.
42:38So what went wrong?
42:41Jack Gillam tells investigators that one year into the Hyatt build, his firm GCE sent drawings of the walkway and
42:48its connection points to the fabricator, Haven Steel.
42:52Haven Steel says that the single hanger rod design is too hard to build, and proposes two sets of rods
42:59instead.
43:01One month later, GCE gives the new walkway design its stamp of approval.
43:11Investigators are mystified.
43:13Gillam's concept for the connection point is flawed from the start, and the new design doubles the load it will
43:19carry.
43:20But at no stage does GCE attempt to rectify the problem.
43:25Why wasn't the mistake spotted?
43:30Now Gillam makes a staggering admission.
43:34Nobody at GCE ran any calculations on the strength of the walkway connections.
43:39He maintains that it's custom and practice in Missouri for the fabricator to do the calculations.
43:45While Haven Steel insists that it's the engineer's job to check the design.
43:54And investigators discover that Gillam had another opportunity to avert catastrophe.
44:00When part of the atrium ceiling collapsed during the build, Gillam's firm did check connections in the atrium.
44:07But nobody checked the walkway connections.
44:12If they had, it's almost certain the problem would have come to light.
44:21The ASCE suspends Gillam.
44:26After five years of litigation, the Missouri State Board holds GCE responsible for the collapse and revokes Gillam's license to
44:35practice in the state of Missouri.
44:39Gillam believes that his firm GCE behaved correctly, but accepts that the bug stops with the engineer of record and
44:47takes ultimate responsibility for the mistake.
44:51The Kansas City Star won a Pulitzer Prize for Wayne Lischke's reports on the Hyatt Skywalk collapse.
44:57Lischke still works as an engineer in Kansas City.
45:03Mark Williams spent two months in intensive care and endured many months more of painful rehabilitation.
45:11But on the opening day of the duck hunting season, I made it.
45:16My physical therapist carried me on his back through the marsh, got me to the duck blind opening day.
45:27Despite suffering a broken back and having both legs torn out of their sockets, Mark made a complete recovery.
45:39Walter and Shirley Trueblood also recovered from their serious injuries.
45:44They're still keen dancers.
45:50The Hyatt Skywalk's disaster transformed engineering safety in the United States.
45:55In the wake of the tragedy, Kansas City completely overhauled its building regulations,
46:00requiring that all load-bearing calculations be checked by a city-appointed engineer.
46:08And the American Society of Civil Engineers rewrote its rules to send a clear message to structural engineers.
46:15You are responsible for the plans that carry your staff.
46:21Today, the Kansas City Hyatt has been transformed.
46:24It no longer has suspended walkways.
46:27In their place stands a single span, supported by sturdy columns,
46:32aimed at instilling a renewed sense of safety and security in those who passed through the now historic site.
46:55well KEYWEIGHT
46:58Zeety재
46:58Americanlock
46:59You
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