The Disaster That Changed Engineering: The Hyatt Regency Collapse

Summary

In 1981, the Hyatt Regency Hotel in Kansas City witnessed a devastating structural failure where suspended walkways collapsed, resulting in over 100 deaths. The cause was traced back to a design change that doubled the load on bolted connections, which were inadequately reviewed. This tragedy serves as a crucial lesson in engineering safety, emphasizing the importance of rigorous design review and the responsibility engineers hold for public safety.

Takeaways

• 🏢 In 1981, the Hyatt Regency Hotel in Kansas City, Missouri, experienced a catastrophic structural failure during a party, resulting in over 100 deaths and over 200 injuries.
• 🔍 The tragedy was the worst structural failure in US history at the time and prompted a thorough investigation into the cause.
• ⚙️ The original design of the suspended walkways included a single pair of hanger rods supporting both the second and fourth-floor walkways.
• 🛠️ A design change proposed by the fabricator and mistakenly approved by the structural engineer led to a critical flaw in the walkway support system.
• 🔄 The design change involved splitting the hanger rods into two sets, which inadvertently doubled the load on the bolted connections of the upper girder.
• 📉 This alteration meant that the second-floor walkway's weight was indirectly supported by the fourth-floor girder, increasing the stress on the connections.
• 🚧 The failure occurred when the load on the connections became too great for the altered design to handle, causing the walkways to collapse.
• 🤝 There is an implicit trust between society and engineers to ensure the safety and accuracy of the structures they design and construct.
• 📚 The Hyatt Regency walkway failure is now a critical case study in engineering education, emphasizing the importance of learning from past mistakes.
• 🔬 Engineers are encouraged to develop and follow conventions and processes that catch and correct errors before they lead to disasters.
• 🌟 The video from Practical Engineering, featuring Grady, highlights the importance of understanding and communicating the implications of design changes in engineering.

Q & A

What was the Hyatt Regency Hotel tragedy in 1981?

The Hyatt Regency Hotel tragedy in 1981 was a structural failure where suspended walkways on the second and fourth floors collapsed during a party, resulting in over 100 deaths and over 200 injuries.

Why was this tragedy considered the worst structural failure in US history at the time?

It was considered the worst structural failure in US history at the time due to the high number of fatalities and injuries, with over 100 people killed and over 200 injured.

What was the original design flaw that led to the collapse?

The original design flaw was a change to the walkway support system, where the hanger rods were split into two sets instead of using a single pair, which doubled the load on the bolted connections.

How did the fabricator's proposed change to the design contribute to the disaster?

The fabricator proposed splitting the hanger rods into two sets to avoid the need for screw threads along the entire length, which was mistakenly approved by the structural engineer without proper review or calculations.

What was the significance of the design change that was overlooked?

The design change meant that the load of the second-floor walkway was indirectly supported by the fourth-floor girder, effectively doubling the load on the bolted connections, which was not accounted for in the calculations.

How did the original design differ from the changed design in terms of load distribution?

In the original design, each walkway's load was independently transferred to the hanger rods. In the changed design, the second-floor walkway's load was borne by the fourth-floor girder, not directly by its own hanger rod.

What was the immediate cause of the walkways' collapse during the event?

The immediate cause was the excessive load on the connections due to the large number of people on the walkways, leading to the box girders splitting open and the walkways collapsing.

What is the 'implicit handshake' mentioned in the script, and why is it important?

The 'implicit handshake' refers to the trust society places in engineers to ensure the safety and accuracy of the structures they design. It's important because it highlights the responsibility engineers have towards public safety.

Why is studying past engineering failures, like the Hyatt Regency walkways, important?

Studying past failures is important to learn from mistakes, develop better conventions and processes, and prevent similar tragedies from occurring in the future.

What is the role of conventions and processes in preventing engineering disasters?

Conventions and processes play a crucial role in catching and correcting mistakes before they escalate, ensuring the safety and reliability of engineered structures.

How does the script suggest we can avoid such tragedies in the future?

The script suggests that by studying and learning from past engineering errors, such as the Hyatt Regency walkways failure, we can improve our understanding and develop better safety measures to prevent similar tragedies.

Outlines

00:00

🏢 Hyatt Regency Walkway Collapse: A Structural Failure Analysis

The video script introduces a tragic event in 1981 at the Hyatt Regency Hotel in Kansas City, where suspended walkways collapsed during a party, resulting in over 100 deaths and over 200 injuries. The incident was the worst structural failure in US history at the time. The cause was traced back to a design change approved by an engineer without proper review, which altered the load-bearing mechanism of the walkways. The original design used a single pair of hanger rods to support both the second and fourth-floor walkways, but a modification suggested by the fabricator split the rods into two sets, inadvertently doubling the load on certain connections. This oversight led to the failure when the connections could not handle the weight of the people on the walkways, causing the box girders to split and the walkways to collapse. The video emphasizes the importance of engineering responsibility and learning from past mistakes to prevent such tragedies.

Keywords

💡Hyatt Regency Walkway Collapse

The Hyatt Regency Walkway Collapse refers to a tragic event in 1981 where suspended walkways at the Hyatt Regency Hotel in Kansas City collapsed, killing over 100 people and injuring over 200. This event serves as the central focus of the video and illustrates the dangers of structural design failures, emphasizing the importance of engineering responsibility.

💡Structural Failure

Structural failure occurs when a building or structure fails to hold the loads it was designed for, leading to collapse or damage. In the context of the video, the failure of the walkways at the Hyatt Regency Hotel was due to a critical design change, highlighting the need for thorough review and calculations in engineering projects to prevent such disasters.

💡Hanger Rods

Hanger rods are structural elements used to support suspended structures, such as the walkways at the Hyatt Regency. In the original design, the rods were supposed to carry the load of both walkways independently. However, a design change made the rods carry additional weight, leading to the walkway collapse. This concept is central to the video’s explanation of the failure.

💡Box Girders

Box girders are horizontal support structures that bear the weight of a structure, often used in bridges and buildings. In the Hyatt Regency case, the box girders were supposed to support the walkways, but the design change led to them carrying excessive load, causing them to split and collapse. This illustrates the importance of understanding load distribution in engineering.

💡Load Distribution

Load distribution refers to how weight is spread across different parts of a structure. In the video, the original walkway design properly distributed the load across hanger rods, but the design change concentrated the weight on a single girder, doubling the load and leading to failure. This concept underscores the significance of proper load analysis in structural engineering.

💡Design Change

A design change refers to an alteration made to the original architectural or engineering plans. In the case of the Hyatt Regency, a seemingly minor change to the hanger rod configuration caused a catastrophic failure. This example highlights how even small deviations in design can have disastrous consequences if not properly evaluated.

💡Fabricator

A fabricator is responsible for constructing elements of a design, such as metal frameworks or girders. In the video, the fabricator proposed splitting the hanger rods into two sets to simplify construction. This proposal, although intended to prevent damage during installation, was not properly assessed, leading to the tragedy.

💡Investigation

An investigation involves a detailed examination to determine the cause of an event or failure. Following the Hyatt Regency collapse, investigators found that the design change was the root cause of the disaster. This investigation serves as a lesson in the video, showing the importance of thorough scrutiny in engineering and design.

💡Engineering Responsibility

Engineering responsibility refers to the accountability engineers hold when designing structures that ensure public safety. In the video, the failure to carefully review the proposed design change before approval highlights the critical role engineers play in preventing disasters. The concept stresses the ethical obligation engineers have to safeguard society.

💡Case Study

A case study is an analysis of a real-world event used to teach lessons or improve understanding. The Hyatt Regency walkway collapse is presented as a case study for engineers to learn from past mistakes. The video emphasizes that studying such failures is crucial in preventing similar incidents in the future.

Highlights

The Hyatt Regency Hotel in Kansas City, Missouri, experienced a tragic structural failure in 1981.

Over 100 people were killed and over 200 injured when suspended walkways collapsed.

The disaster was the worst structural failure in US history at the time.

Investigators discovered a design change that was mistakenly approved by the structural engineer.

The original design called for a single pair of hanger rods for each walkway.

The fabricator proposed splitting the hanger rods into two sets to avoid long screw threads.

The design change was approved without detailed review or calculations.

The new design doubled the load on the bolted connections.

The load of the second-floor walkway was indirectly borne by the fourth-floor girder.

The failure occurred when the load on the connections became too great for the altered design.

The box girders split open, leading to the collapse of both walkways.

The engineering community has a responsibility to ensure the safety of the public.

Engineers must develop conventions and processes to catch and correct mistakes.

The Hyatt Regency walkways failure is a crucial case study in engineering education.

The goal is to prevent such tragedies from occurring again.

Practical Engineering's video on hydrostatics is recommended for further viewing.

The next guest video will feature a prop that has been to the moon.

Transcripts

Today’s guest video is from Grady at Practical Engineering.

He’s talking about a tragedy:

and the lessons we learned and the reasons why it happened are fascinating.

Also, he made his own props.

Grady, take it away.

In the summer of 1981, the Hyatt Regency Hotel in Kansas City, Missouri,

hosted a large party in the multi-story atrium area.

During the event,

suspended walkways on the second and fourth floors collapsed,

killing over 100 people and injuring over 200 more.

At the time, the accident was the worst structural failure in US history.

In the wake of the disaster,

investigators discovered a change to the original design of the walkways

that was proposed by the fabricator and mistakenly approved by the structural engineer.

What, at first glance, seemed like a subtle adjustment to the design,

turned out to be the root cause of the failure.

Two suspended walkways spanned the atrium in the Hyatt Regency

with the second-floor walkway directly below the fourth-floor walkway.

Each was supported by a series of box girders

suspended by hanger rods and retained by nuts and washers.

The original design called for a single pair of hanger rods,

which would pass through each fourth-floor girder to the second-floor girder below.

The fabricator responsible for constructing the walkways objected to this plan

because it would require screw threads for the entire length of the hanger rods,

which could easily be damaged during construction.

So, they proposed to split the hanger rods into two sets.

One to connect the fourth-floor walkway to the roof

and one to connect the second-floor walkway up to the fourth-floor girders.

If you don’t notice the significance of this change, you’re not alone.

It was approved by the engineer without a detailed review or calculations,

which would have revealed its inherent flaw.

In this setup, which represents the original design,

the load of the two walkways is independently transferred to the hanger rods.

Notice how I can lift each girder without affecting the other.

Now, let’s look at the design change.

In this configuration,

notice that the entire weight of the second-floor walkway is being borne

not directly by the hanger rod,

but instead, by the girder above.

If I lift the fourth-floor walkway, the second-floor walkway is lifted as well.

The hanger rods are still carrying the same load at the top,

but the two nuts on the upper girder are supporting the weight of both walkways.

This simple change effectively doubled the load on those bolted connections.

Imagine that you and a friend are both hanging on a rope.

The original design is the equivalent of you both holding onto the rope independently,

whereas the design change is the equivalent of your friend hanging onto your ankles.

The total weight supported by the rope is the same in both cases,

but your likelihood of maintaining a grip is not.

This subtle change was identified by investigators as the primary cause of failure.

With so many people on the walkways that evening,

the load on the connections was too great.

The box girders split open, slipping past the washers and nuts

leading to the collapse of both walkways.

There is an implicit handshake between a society and its engineers.

We hardly have a choice but to trust that the constructed environment that we live in

is safe and sound.

When an engineer seals a design,

he or she takes responsibility for its accuracy and safety to the general public.

But the err is human and that includes engineers.

So, we try to develop conventions and processes

that can catch and correct from mistakes before they get too far.

And that includes studying and learning from errors made in the past.

The failure of the Hyatt Regency walkways is an important case study

taught to nearly every engineer

with the goal that such a tragedy will never occur again.

Practical Engineering is filled with great videos, so go subscribe!

I would recommend starting with Grady’s video on hydrostatics.

Next time,

a guest video with a prop that has been to the moon.