“In an earthquake similar to the ’06 event many of the City’s buildings constructed with ”non-ductile concrete”—many built between the ‘30s and the ‘70s—will flatten like pancakes leaving more people dead in one building than in all the wood frame buildings combined.”—Anonymous public official
I have a friend who lives in the Fontana East, and another who lives in the Comstock Apartments on Nob Hill, I wish they would read this, so they could become advocates for better reinforcements to their own buildings. There are department stores, schools, parking structures and office buildings throughout California that endanger our lives. Non-ductile concrete buildings often have large open stories on the ground floors held up by unreinforced or poorly reinforced concrete columns.
The next big one is not an unlikely event, it is an eventuality. A major quake on the Hayward fault is 2/3 more likely to occur within the next 9 years than a quake at a more remote site, so the experts say. When that happens, if at 7.1 on the Richter scale, these NDC buildings will, in many cases “pancake” completely to the ground, killing hundreds per building.
When the Hayward Fault ruptures, if it is as strong, as the ‘89 Loma Prieta quake, we will feel it 10 times more, because we are so much closer to the Hayward fault than we are to the Loma Prieta fault.
Unlike San Francisco, Los Angeles is beginning to prepare for the next big one by making an inventory of the non-ductile concrete buildings within its boundaries. “Among the buildings which performed the worst were,” according to the California Seismic Commission report on the 1995 Northridge Quake, “Buildings constructed with suspect materials and techniques, such as tilt-ups, non-ductile concrete frames (NDC), and unretrofitted unreinforced masonry (URM). Buildings designed or constructed with irregular configurations—for example; multistory buildings with inadequately braced first stories (like most of the apartment houses that collapsed) and hillside homes.”
Yet, 13 years later, the State has not taken any corrective measures, such as mandating the retrofitting of these NDC buildings and San Francisco has not even ordered that an inventory be done to determine which buildings would be most likely to collapse in a strong earthquake.
Although our Building Dept has such an inventory way down on the “To Do List.” They have a hunch that there are hundreds of buildings that would be on such a list. Nevertheless, they are tackling the issue of “strengthening” the soft story, 3-4 story buildings, like the ones that collapsed in the Marina, in our 1989 quake.
The Fontana East and West are two well-known NDC buildings. I believe the Comstock Apartments, on Jones Street, north of Grace Cathedral is another, and I suspect that the Avalon Tower, just east of 7th and Lawton, as well as the Park Merced Towers may also be NDC buildings. It is important to know how safe our buildings are so that we can begin to address the retrofit of these buildings.
Suspecting that there are many in the City, I have asked our Building Dept to determine which buildings are NDC, and what the total is. The reply: “We will get to it, eventually.”
One reason for the foot-dragging might be the costs associated with the retrofits. The cost will not be feasible for some, and for those that can be strengthened, it will cost a ton of money. Bummer, but ignoring this “Sleeping tiger” is going to greatly increase the amount of death and damage to the City, and our public officials are turning a blind eye to the problems.
Building owners as well as business owners may not want to have their building on such a list, as it would undoubtedly be reflected in their bottom-line, and that may be the root cause of this unexplainable reluctance by officials who otherwise consistently root around in everyone’s business seeking to impose fines and fees. Many in the business community fear their businesses will be out on the street if retrofitting is required but we must tackle this problem now.
The Building Dept. is NOT a policy-making Department. Therefore, it seems, we citizens have to get our Mayor and Supervisors to set policy here. To me—in my ignorance as a mere realtor—I’d like to know if the building I’m selling my customer is a death trap and I think the customer has a right to know.
In 2006 there was a Conference of Engineers here in San Francisco that issued a report with chilling data. In support of the Pacific Earthquake Engineering Research (PEER) Center’s Performance-Based Earthquake Engineering (PBEE) Framework, fatality and injury models have been developed for non-ductile concrete frame (NDCF) structures using available population survey data from the Kocaeli Earthquake of August 17, 1999. Population-based survey data for the City of Gölcük provides specific information on sample population demographics, deaths and injuries, building type, building damage, the injured’s location within the building, and action taken at the time of the earthquake. Fatality and injury rates have been developed for NDCF structures suffering partial and total collapse, as well as selected other damage conditions (e.g., non-collapse structural damage, damage limited to non-structural and contents damage only). The resulting casualty rates may be compared to available published models, which are often based on expert opinion and limited historical data.
In the “tables” that are in this report, they project at least “20% fatality rate” where there will be “total collapse” of buildings!
In May of 2008, ShakeOut Scenario, a study done at UCLA, a 7.8 San Andreas quake clarifies that a systematic research on cataloguing the NDRCB stock in Riverside County, and assessing their collapse risk is an urgent need.
“Existing stocks of vulnerable structures arguably constitute the most critical hazard risk in seismic regions of the United States. A considerable portion of this stock consists of Nonductile Reinforced Concrete Buildings (NDRCB’s)—a term used to signify a reinforced concrete structural system that has very limited capacity to absorb and dissipate the destructive energy of strong ground shaking beyond its limited elastic range, and hence, one that is extremely vulnerable to collapse.
Seismic design of reinforced concrete structures was at its infancy in 1950’s, and lacked critical improvements to detailing requirements until 1970’s. The watershed event that is typically cited to delineate the commencement of ductile reinforced concrete design is the 1971 San Fernando Earthquake. Observations of the performance of reinforced concrete buildings in this event and subsequent studies led to improved provisions that appeared in the 1976 Uniform Building Code. These design provisions and requirements have been further improved ever since.”
A bit into the report you find “An important conclusion of a recent study by Kircher et al. (2006) suggest that 50% of the expected casualties in a repeat of the 1906 San Francisco Earthquake will be due to 5% of all the building stock. This small percentage comprises NDRCB’s as well as soft-story wood and unreinforced masonry structures. The same study estimates that a M7.9 rupture of the San Andreas Fault will kill more than 1,800 and seriously injure 8,000 people if it occurs during the night. During the daytime these figures climb to 3,400 and 12,500, respectively.
Nevertheless, it is stated in the same study that little data on the actual number and square footage of NDRCB’s were available. It was assumed that all pre-1974 concrete buildings were collapse hazards. Furthermore, a validation study performed with data from the 1989 Loma Prieta Earthquake indicated that the loss estimates could be as high as twice of what may actually occur, somewhat quantifying the uncertainty in these predictions.
Note: the “soft story wood” type is what partially collapsed in our Loma Prieta quake. Since they are 2–4 stories, they are much less likely to totally collapse, compared to a 20 story concrete and glass tower.
One report that stands out cites a Seismic official for the L.A. Building Department. He flatly says that “all non-ductile concrete buildings” should be torn down, they are so unsafe.
After some research and more than one sleepless night, I wrote to the City’s point person on Seismic issues and standards, citing my concern that SF was doing nothing. Lawrence Kornfield, Chief Building Inspector, Department of Building Inspection. He wrote back to me about the “Concrete Coalition” bringing these problems to the fore and developing retrofit/repair and other options. He informed me about the website http://www.concretecoalition.org/.
There is no list of hazardous concrete buildings in San Francisco; each building must be separately evaluated by an engineer to determine its level of risk. Over the next two years, the CAPSS program will attempt to understand the scope of problems related to these and other building types in San Francisco, although we will not be doing an inventory of specific at-risk buildings. Priorities of seismic hazard mitigation are done either by the State, through the adoption of codes and laws, or by local government, which may amend the State codes. Concrete building upgrade is particularly problematic as the buildings often require extensive engineering analysis and design; are usually massive structures, requiring extensive and expensive structural upgrade work; are often owned by multiple owners (like condominiums); and require upgrades that often intrude into usable space or require closing windows or doors.”
On the other hand, I feel that IF the Mayor and Supervisors asked some questions, we might, as a City, get some answers about the “Houses of Pancakes” that so many folks in S.F. live in.
We need to know:
1) What defines a Non-Ductile Concrete Building?
2) How can we aggregate the list of buildings that match that profile?
3) How can we check the records in the microfilm archives of DBI to see which of these buildings are, in fact “Non-Ductile Concrete” type?
4) What comments and recommendations for retrofits/tear downs do local, statewide, and national officials and experts suggest?
5) What can be inferred from all the “casualty modeling” of the performance of NDC buildings, found in the data of the past 14 years?
If the state has to come up with a “New Standard for Dealing With Non-Ductile Concrete Buildings” they have to do this sooner rather than later, in view of the ticking time bomb that the Hayward Fault represents. San Francisco has the most to lose, when that ruptures, given how many NDC buildings it seems we have. We can’t just sit and fiddle while “Sacramento does its thing, or drags and delays the doing of it” Since, literally, it’s not “their fault” that is ticking away, louder and louder, but ours.
San Franciscans deserve to have answers to these 5 key questions, in a simple, easy to read report. And then “Let the Chips Fall Where They May”, so to speak, but let us all be not lulled into non-action, due to “non-reporting of accumulating evidence.”
Jack Barry is a realtor living in the Sunset.