As California braces for the next major earthquake, the safety of Los Angeles’ skyscrapers is under scrutiny. This blog post explores the vulnerability of the city’s high-rises, the lessons learned from past quakes, and the steps being taken to ensure these towering structures can withstand the shaking. With a focus on the Gas Company Tower and the county’s plans to relocate, we delve into the engineering challenges and the potential consequences of a catastrophic collapse. Earthquake engineering and seismic retrofitting are key topics discussed.
Assessing the Risks
The Gas Company Tower in downtown Los Angeles, shown last month, is among the tallest and most prominent skyscrapers in the city. of one of its most prominent skyscrapers, the Gas Company Tower. The tower was built in 1991, so it’s fairly new, though a modern date doesn’t ensure its sturdiness against an earthquake.
The Northridge quake in California back in 1994 proved that even steel-framed buildings, considered the most quake-proof of all, are capable of suffering considerable damage during larger quakes. The county is in the process of a complete structural evaluation of the tower, which will help explain how it would hold up next to the out-of-dated Kenneth Hahn Hall of Administration, as well as if it could replace it. The attention highlights the new awareness of how just infirm so many of this city’s soaring skyscrapers are, regardless of what they’re built from and when they went up.
Lessons from the Past
The failure of connections in the Northridge earthquake led to revelations about serious design and construction flaws for steel moment frame buildings; steel moment frames are a common means of bracing large buildings against seismic activity by ensuring that horizontal beams connect securely to vertical columns so that neither shifts concerning the other during a quake. Welding, the choice of improper filler metals, and the very nature of these connections have been found problematic. Now measures have been taken to address these weaknesses through the types of construction, but the danger remains.
With the county considering all its options, what remains clear is that a collapse would only make matters worse. A magnitude 7.8 earthquake on the San Andreas Fault could cause as many as five steel moment frame high-rise buildings to collapse in Southern California, where tens of thousands of people could become trapped when they are cut off by collapsed overpasses and crippled roads. These are high stakes, and a mistake by the country could put countless people in the region’s sky-high condos at risk.
Fortifying for the Future
The design of the Gas Company Tower features a double structural system that combines its steel moment frames with a braced core, which could offer more resistance and flexibility in an intense quake. Nevertheless, any retrofitting for the existing building will still be fully subject to a more comprehensive, up-to-date seismic performance evaluation.
The broader public policy challenge for the county is deciding how to pay for systemic upgrades of thousands of seismically vulnerable buildings in the city, which include even more dangerous nonductile concrete structures. The tricky balance between the cost of retrofitting versus demolition and reconstruction is a critical one, yet it will help keep the people — both residents and tourists who use Los Angeles’ buildings safe. The choices of today will determine whether a city is doing it all over again by falling in another big quake and losing its signature Skyline for generations to come.
