Ep 7. Chicago's Tower Of Terror

In Engineering Catastrophes season 3 episode 7, titled "Chicago's Tower Of Terror," viewers are taken on a journey to the Windy City to explore one of the most iconic buildings in its skyline: the Hancock Tower. Designed by architect Bruce Graham, the Hancock Tower was completed in 1969 and quickly became a symbol of Chicago's industrial and architectural might. With its signature X-bracing, the tower was engineered to withstand the powerful winds that whip through the city, but as this episode reveals, even the best-laid plans can be foiled by unforeseen circumstances.

The episode opens with aerial footage of the Hancock Tower, showcasing its impressive height and unique design. We then hear from experts in the field of architecture and engineering, who explain the significance of the tower and its importance in Chicago's history. From there, the episode delves into the first signs of trouble that appeared just six years after the tower was completed.

In 1975, the residents of the Hancock Tower began to notice an unsettling phenomenon: the building was swaying. At first, the movement was barely perceptible, but as time went on, it became more pronounced. Experts were brought in to investigate, and what they discovered was alarming: the tower was swaying more than two feet in either direction, far beyond what was considered safe.

The cause of the swaying was traced to a design flaw in the tower's X-bracing system. When the tower was first built, the engineers had used low-quality steel for the braces, which had weakened over time. This, coupled with the high winds that are common in Chicago, had led to the dangerous swaying. The episode goes into detail about how engineers tackled the problem: by installing a tuned mass damper, a massive weight that sits at the top of the building and counteracts the motion caused by the wind.

Despite the installation of the damper, concerns about the tower's safety persisted. In 2018, a new problem emerged: the building's windows were cracking. This was particularly dangerous, as the Hancock Tower's windows are nearly floor-to-ceiling and can weigh up to 500 pounds. If they were to fall, they could cause catastrophic damage to the streets below.

Once again, engineers were brought in to investigate. What they discovered was astonishing: the windows were cracking due to a phenomenon called thermal stress. When the sun hits the tower's dark glass façade, it causes the glass to expand and contract rapidly, which can lead to cracks. The episode explains in detail how engineers addressed this problem by installing cooler glass panels and creating a ventilation system to circulate air between the glass and the building's steel frame.

Throughout the episode, viewers are treated to stunning visuals of the Hancock Tower, including a climb to the top by a team of engineers and a look at the building's intricate inner workings. We also hear from residents of the building, who describe what it's like to experience the swaying and cracking first-hand. The episode ends with a look at how the tower has become one of Chicago's most enduring symbols, even in the face of the engineering challenges it has faced over the years.

Overall, "Chicago's Tower Of Terror" is a fascinating look at one of America's most iconic buildings and the engineering challenges that have plagued it. The episode manages to balance technical explanations with stunning visuals and personal anecdotes, making it a compelling watch for anyone interested in architecture or engineering.