How would California's skyscrapers behave in the event of a major earthquake?

On paper, the deal makes sense.

Faced with the prospect of extensive and costly seismic safety modifications to its 1960s downtown headquarters, Los Angeles County decided to examine an alternative: a much newer building just a few blocks away. Not only was it built to more stringent standards, the reasoning went, but it was available at a significant discount to its pre-pandemic price.

But the potential move to the gas company tower is far from official. Before signing the deal, officials want to assess how earthquake-proof the skyscraper is.

The audit underscores a growing understanding of the structural weaknesses of many buildings across Los Angeles, which has led to a steady pace of regulation requiring the reinforcement or demolition of at-risk structures.

Many of these rules, and much of the attention of policymakers, have focused on older buildings or those made of materials known to be susceptible to vibration—such as unreinforced brick or non-ductile concrete.

But the Gas Company Tower is different. It is relatively new, completed in 1991, and made of steel.

But as the 1994 Northridge earthquake showed, common types of steel-framed buildings are still vulnerable to severe damage during strong quakes. During that magnitude 6.7 quake, 25 steel-framed buildings were severely damaged, including the Automobile Club of Southern California building in Santa Clarita, which nearly collapsed.

Kenneth Hahn Hall of Management debuts downtown

(Gary Coronado/Los Angeles Times)

Even more disturbing is that California’s earthquakes over the last half-century have not been a true test of the kind of shaking California’s high-rise buildings are likely to experience. Neither downtown Los Angeles nor San Francisco has experienced “severe” earthquake-induced shaking since the steel-scraper era began in the 1970s, according to the U.S. Geological Survey’s definition of earthquake intensity.

Other cities in Los Angeles County—such as Torrance, Santa Monica and West Hollywood—generally require buildings like the Gas Company Tower to be evaluated for earthquake resistance and retrofitted if necessary. The city of Los Angeles does not.

But seismic engineers are conducting an “in-depth assessment” to determine whether the gas company tower, the fifth-tallest building in the downtown skyline, has weaknesses that need to be addressed, according to a Los Angeles County spokesman.

“These issues are exactly what we are exploring through our ongoing efforts,” the county said in a statement. “Without preempting the work currently underway, one factor is to evaluate the performance of this building compared to the performance of the administration hall, and the costs involved in each approach.”

The county has submitted a nonbinding letter of interest in the 52-story, 749-foot building, though the Board of Supervisors still must approve the deal.

With demand for downtown office space low, the county plans to pay $215 million — a significant discount from the more than $600 million it was valued at before the pandemic. But that price doesn’t include any potential upgrade costs.

The tower, located at 555 W. 5th St., was completed to stronger seismic standards than one of the buildings it is likely to replace: the nearby Kenneth Hahn Hall of Administration, which was completed in 1960.

The administration hall is the headquarters of the nation’s most populous county—home to its top elected officials: the five-member Board of Supervisors. The sprawling building is located in the Civic Center, about three-fifths of a mile northeast of the skyscraper.

Downtown Los Angeles

(John W. Adkisson/Los Angeles Times)

But like the decades-old gas company tower next door, it may still need some seismic work.

It is one of several Los Angeles skyscrapers that incorporate a steel frame as part of its structural system. These frames consist of horizontal beams and vertical columns, and feature a largely rectangular structure. Steel frame buildings rely on the connections between the horizontal beams and vertical columns to remain intact during earthquake shaking, keeping the building structure together.

(Steel moment frames differ from steel-reinforced frames, which have diagonal braces added to create triangular shapes. Triangles are more rigid than rectangles and strengthen the overall structure. Steel-reinforced frames bend less in an earthquake than steel moment frames.)

The steel moment frames were discovered to be a potential problem after the Northridge earthquake, which killed at least 57 people. No buildings of this architectural style collapsed or killed anyone, but some were so badly damaged that they had to be demolished.

Among the defects in steel buildings prior to the Northridge earthquake were problems with welding and inspection techniques, filler metal used in welds, and the basic configuration of the connections between vertical columns and horizontal beams. After the earthquake, changes in construction methods were implemented to address such problems.

For the steel moment frames, “Northridge showed us that the connections were vulnerable to damage,” said David Cook, former president of the Earthquake Engineering Research Institute and co-founder of the Gardena-based structural engineering firm Structural Focus.

In a worst-case scenario, a steel-frame building could collapse during a strong earthquake, although this has not happened in the United States.

It’s still unclear how vulnerable the gas company tower is, and experts say more study is needed to find out. In general, concrete buildings that need repair — like the administration hall — are more vulnerable than steel buildings that need to be reinforced for earthquake resistance.

The gas tower doesn’t just rely on its steel frames to resist earthquakes, said Prabhud V. Panavalkar, the building’s structural engineer. Instead, it uses a double-beam structural system that includes a braced core. This design reduces stress on the joints between horizontal beams and vertical columns that are tested by earthquake vibrations.

Gas Company Tower in Downtown

(Myung-Je Chun/Los Angeles Times)

The U.S. Bank Tower and the Figueroa skyscraper in Wilshire — both of which he was the structural engineer for — also use a double-frame structural system, Panavalkar said.

Steel-frame buildings have suffered extensive damage in the United States and abroad. In 1995, a single story of a steel structure collapsed during a 6.9 magnitude earthquake in Kobe, Japan. According to a report by the U.S. Geological Survey, one-third of the 630 modern steel buildings in the area that were severely damaged were damaged.

In a 2008 report titled “The Earthquake Scenario,” structural engineers cited “the collapse of some welded steel-framed buildings built before 1994 is a plausible scenario,” and it is plausible that five high-rise welded steel-framed buildings in Southern California could collapse in a hypothetical magnitude 7.8 earthquake on the San Andreas Fault.

In such an earthquake, many buildings would experience shaking that would last about two minutes, much longer than the seven- to 15-second period of movement in 1994, according to the U.S. Geological Survey.

Although the 1989 Northridge and 6.9-magnitude Loma Prieta earthquakes were very frightening to many people, their epicenters were far from downtown San Francisco and Los Angeles, producing “strong” or “very strong” shaking in the center of those cities. This type of shaking—as defined by the Modified Mercalli Scale of Earthquake Intensity—is milder and less damaging than the “strong” shaking felt in part of Santa Cruz County in 1989 and the “violent” shaking felt in part of the San Fernando Valley in 1994.

Unreinforced brick buildings, non-ductile concrete buildings, and unprepared liftable buildings are much more dangerous than steel-framed buildings, and there are many examples in California where these types of structures have collapsed. “But that doesn’t mean they’re [steel moment frame buildings] “It should not be evaluated and modified,” Cook said.

If just one steel-frame building collapses in an earthquake, the results would be catastrophic. The USGS says the hypothetical five buildings that could collapse completely in a strong quake could have 5,000 people inside.

The question is whether the gas tower needs seismic modifications to handle a strong earthquake. A reinforced core helps with that. In general, the core provides stiffness and strength to help the building handle side-to-side vibrations, Cook said.

A fresh seismic analysis of the building would be helpful because seismic assumptions have changed so much since it was designed. Scientists say the ground shaking caused by an earthquake now could be much worse than previously thought, and buildings in downtown Los Angeles and San Francisco have not been tested against the kind of intense shaking we now know is possible.

“the [seismic] “The loads these old buildings were designed to withstand were much lower in the 1980s,” said Daniel Zepeda, a structural engineer with Degenkolb Engineers.

Other developments since the skyscraper was built include the discovery of a new earthquake fault.

The Puente Hills Fault System, which underlies large swaths of downtown Los Angeles, southeastern Los Angeles County, the San Gabriel Valley and northern Orange County, was discovered by scientists only in 1999. The fault system has the potential to trigger a magnitude 7.5 earthquake, and one simulation suggests that such an event could kill between 3,000 and 18,000 people.

It's unclear how much it would cost to renovate the skyscraper if necessary, but because the Gas Company Tower has a double structural system that includes a reinforced core, it could ultimately be cheaper than if it had just a steel frame, Cook said.

Although some praised the county for moving to buy the skyscraper for “cheap” and argued that such a sale would revitalize downtown, most members of the Board of Supervisors have remained silent on the proposal, which was negotiated by the executive office. Supervisor Janice Hahn was the lone exception, claiming that the county has no interest in leaving the Civic Center, where many of Los Angeles’ government buildings are clustered.

LOS ANGELES – October 28, 2019: Angel's Journey in downtown Los Angeles, USA. The funicular dates back to 1901.

(f11photo – stock.adobe.com)

The Boardroom is named after Hahn's father, the late Kenneth Hahn, after he retired after serving a record 10 terms as superintendent. Hahn represented South Los Angeles from 1952 to 1992, and died in 1997 at the age of 77.

The county has some steel-framed buildings, but it has not compiled a comprehensive list like it has for its non-ductile concrete buildings, the chief executive said. Officials said there are no immediate plans to retrofit steel buildings to withstand earthquakes, with the focus on rehabilitating the most dangerous structures.

Moving county offices to the gas tower doesn’t solve the problems with the county’s earthquake-prone, non-ductile concrete buildings, and questions remain about whether they should be rehabilitated, demolished, sold or left empty. The Board of Supervisors voted last year to ask officials to draft new rules that would require the rehabilitation of county-owned non-ductile concrete buildings, as well as any buildings in unincorporated areas.

Although the administration hall is the most prominent, the county has other facilities made of non-malleable concrete. Among the most important of these are the medical examination department, where officials perform autopsies; and the headquarters of the departments of public health and health services.

Even if the building is empty, the collapse of just one building could injure or kill nearby people and motorists, and possibly cast a shadow over its neighbors — such as the Civic Center — for years.

What Are The Main Benefits Of Comparing Car Insurance Quotes Online

LOS ANGELES, CA / ACCESSWIRE / June 24, 2020, / Compare-autoinsurance.Org has launched a new blog post that presents the main benefits of comparing multiple car insurance quotes. For more info and free online quotes, please visit https://compare-autoinsurance.Org/the-advantages-of-comparing-prices-with-car-insurance-quotes-online/ The modern society has numerous technological advantages. One important advantage is the speed at which information is sent and received. With the help of the internet, the shopping habits of many persons have drastically changed. The car insurance industry hasn't remained untouched by these changes. On the internet, drivers can compare insurance prices and find out which sellers have the best offers. View photos The advantages of comparing online car insurance quotes are the following: Online quotes can be obtained from anywhere and at any time. Unlike physical insurance agencies, websites don't have a specific schedule and they are available at any time. Drivers that have busy working schedules, can compare quotes from anywhere and at any time, even at midnight. Multiple choices. Almost all insurance providers, no matter if they are well-known brands or just local insurers, have an online presence. Online quotes will allow policyholders the chance to discover multiple insurance companies and check their prices. Drivers are no longer required to get quotes from just a few known insurance companies. Also, local and regional insurers can provide lower insurance rates for the same services. Accurate insurance estimates. Online quotes can only be accurate if the customers provide accurate and real info about their car models and driving history. Lying about past driving incidents can make the price estimates to be lower, but when dealing with an insurance company lying to them is useless. Usually, insurance companies will do research about a potential customer before granting him coverage. Online quotes can be sorted easily. Although drivers are recommended to not choose a policy just based on its price, drivers can easily sort quotes by insurance price. Using brokerage websites will allow drivers to get quotes from multiple insurers, thus making the comparison faster and easier. For additional info, money-saving tips, and free car insurance quotes, visit https://compare-autoinsurance.Org/ Compare-autoinsurance.Org is an online provider of life, home, health, and auto insurance quotes. This website is unique because it does not simply stick to one kind of insurance provider, but brings the clients the best deals from many different online insurance carriers. In this way, clients have access to offers from multiple carriers all in one place: this website. On this site, customers have access to quotes for insurance plans from various agencies, such as local or nationwide agencies, brand names insurance companies, etc. "Online quotes can easily help drivers obtain better car insurance deals. All they have to do is to complete an online form with accurate and real info, then compare prices", said Russell Rabichev, Marketing Director of Internet Marketing Company. CONTACT: Company Name: Internet Marketing CompanyPerson for contact Name: Gurgu CPhone Number: (818) 359-3898Email: [email protected]: https://compare-autoinsurance.Org/ SOURCE: Compare-autoinsurance.Org View source version on accesswire.Com:https://www.Accesswire.Com/595055/What-Are-The-Main-Benefits-Of-Comparing-Car-Insurance-Quotes-Online View photos