The biggest threat to skyscrapers around the world might not be terrorism, fires, hurricanes or earthquakes. It might be money.
by Jessica Cilella, Web Editor
That’s one argument panelists made during our “Securing Tall: What’s the Biggest Threat to a Skyscraper” panel discussion on May 18.
The event was the second in a four-part Skyscraper Lecture Series hosted by CAC and The Council on Tall Buildings and Urban Habitat (CTBUH). The next lecture, Greening Tall: Naturalizing the Vertical Realm, will take place this fall.
CTBUH Executive Director Antony Wood moderated the program. At one point, he asked the audience to vote for which threat they thought would be mostly likely in a San Francisco high-rise: an earthquake, fire, terrorism or other. The answers were almost equally split.
Each panelist had experience securing skyscrapers from varying threats. Technical coordinator Nicole Dosso of SOM worked on her company’s projects at the World Trade Center site, including One World Trade. Having witnessed the 9/11 attack and played a major role in the site’s reconstruction, Nicole said she believes a terrorist attack is still a skyscraper’s biggest threat because it is “truly the unknown.”
For safety purposes, One World Trade has a minimal amount of glass, but the designers worked to emulate a feeling of natural light. The building also features 30-inch concrete walls, separate elevators for firefighters and a large number of cameras and other security measures in the lobby. The exterior design disguises the intakes for the life safety systems, to prevent them from becoming targets. Bollards—short vertical posts that are increasingly being used to secure areas from car ramming attacks—surround the exterior as well.
However, terrorism wasn’t the only threat that had a direct connection to One World Trade. In 2012, Hurricane Sandy caused extensive water damage to the site while the building was under construction, resulting in some demolition and rebuilding to be more storm resistant.
“9/11 and Hurricane Sandy have altered the way buildings are constructed for security, life safety and resiliency,”
Simon Lay, a fire risk engineer and director of Olsson Fire & Risk, pointed to the soon-to-be-constructed Leeza Soho building in Beijing as an example of a high-rise design with heightened fire risk. Inside will be the world’s tallest atrium, extending more than 600 feet, which could become very hazardous if a fire occurred.
“When a building is really tall, you might actually stay in there for the entirety of the fire situation,” he said. “Understanding the consequence of structural fire failure is really important in tall buildings.”
Simon’s company is constantly looking at ways to improve evacuation times in tall buildings too, by using probabilistic fire risk assessment. This has been helpful in mixed-use buildings, which are growing in popularity, but also increasing fire risk in many buildings, due to higher probabilities of a fire starting. For example, Simon said, people running businesses in their homes that should be happening elsewhere—like creating hair or beauty products—are forming dangerous situations in high-rises around the world.
“We don’t tend to worry about threats in tall buildings, perhaps because there are building codes and building codes tell us the buildings are going to be safe,” he said. “Assuming the buildings are safe because you followed the building code is where that threat lies.”
MKA President Don Davies, a structural engineer with extensive experience working on buildings in areas of high seismicity, said most threats to high-rises can be managed, but it can be costly to do so. He believes many preventative measures being taken on tall buildings on the West Coast should be repeated elsewhere. For example, he said, un-reinforced masonry within a seismic area is against the law in California.
“You have to mandate it at a governing body level because people are not going to want to spend the money,” he said, adding that many areas of the world need to improve in-fill systems and do more to prevent falling hazards.
Don added that climate change and increasingly extreme weather are pushing engineers to follow nature’s lead and catch up.
”I think we do a pretty good job on our buildings for life safety. Our buildings generally aren’t going to fall over,” Don said. “But façade platting damage and the resulting water and mold and the economics to try to repair that—that can do a building in really quickly.”
Buildings are already being designed to the extremes—Don said his company looks at the predicted strength of windstorms that occur only once every 1,700-years—but Antony said the challenge is building them to last forever.
At one point during his presentation, Antony showed a picture of a lion walking through an abandoned Times Square covered in jungle plants. What happens if rising water levels or unbearably warm temperatures make New York City a place that is no longer economical to maintain?
“Maybe this is a little doom and gloom, but I just wonder if humanity, at some point in the future, will see a time where actually we begin to realize there’s certain cities that are unviable,” he said, adding that perhaps one day cities will be constructed for 100 or 200 million people in less risky locations.
Antony said financial downturns are huge threats too, as seen with the world’s largest high-rise slum—the unfinished 45-story Tower of David in Caracas, Venezuela—and whole cities in China that are empty because developers misjudged the market.
Adaptive reuse—a popular concept that the panelists said everyone is still trying to figure out—is highlighting the need to select the right materials for refurbishments that can withstand threats. Design flaws, or “professional incompetence” is a big risk that has resulted in tragedies when threats hit a building.
Antony also noted that the highest tower ever dismantled was only about 600-feet high and it’s been nearly 50 years since it was taken down.
“One of the things I’m interested in is how long should we design these buildings for? What is the life cycle of these buildings? We’re building these buildings and we have no idea how we’re going to take them down.”
Despite discussing the many negative possibilities they have to think about in their jobs, the panelists agreed buildings have grown more secure in recent years—and as architects learn and experiment more, skyscrapers will continue to become safer.