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KNOWLEDGE IS RESPONSIBILITY: ARE LOS ANGELES OFFICIALS HIDING THE TRUTH ABOUT HI-RISE EARTHQUAKE VULNERABILITIES?

I remember the January 17th, 1994 Northridge quake vividly as I was shaken awake in the most violent earthquake I have ever experienced. Located in West Los Angeles, between the collapsing I-10 Freeway bridge to the East and a collapsing medical building to the North, our home suffered a cruel fate, having moved off its foundation to such a degree as to be "red tagged" as being unsafe for human occupancy. An experience that I would rather not repeat in my lifetime.

And yet as I watched the television news, I see Dr. Lucille Jones, the noted seismologist who works for the United States Geological Survey and a member of the California Seismic Safety Commission, briefing a seismic safety panel gathered in Coachella Valley. Her words are extremely ominous as she describes the consequences of a large quake centered in California's Coachella Valley, southeast of Los Angeles, and located between two powerful and dangerous faults: the famed San Andreas fault and the equally powerful San Jacinto fault.  What made this briefing even more scary was the fact that she was describing an area that was approximately 300 years overdue for a major quake. Not one to be taken lightly, she described a quake scenario that could potentially topple buildings in Los Angeles.

One the day of the presentation, a magnitude 4.6 quake struck tens of miles from my present home. Enough to raise momentary concern as it was centered in the far reaches of Northridge. Followed a few days later by a more gentle 3.5 magnitude temblor.

Which made me think of my late friend Nick, a movie special effects guru and certified welder and his rants on welds in certain Los Angeles high-rise buildings. Nick was convinced that hundreds of welds were potentially compromised and that, at this late date, nobody was routinely re-inspecting the weld joints. Laughingly he proposed a weld-inspection business where everybody from the owner, the insurance company, the contractors architects and engineers hated you. Joking it was like being the fire marshal or designated safety officer on a small budget movie.

Considering that my sister works on the 18th and top floor of a West Los Angeles high-rise building, I decided to revisit the subject of high rise buildings and their suitability to ride out a severe jolt.

It all started with the January 17, 1994 Northridge Earthquake which registered a magnitude of 6.7 and lasted for approximately 15 seconds. When the shaking stopped, 51 people were dead and 9,000 people were injured. The loss of life was limited due to the quake striking at the early morning hour of 4:30 a.m when most people were still at home. This quake has been the largest and costliest quake in recent times, with $44 billion dollars in damage, 25,000 dwellings uninhabitable, 7,000 buildings red-tagged (no occupancy), 22,000 buildings yellow-tagged (limited access), 9 hospitals closed, 9 collapsed parking  garages, major structural damage to 11 roads into Los Angeles forcing closure, 2 bridges on the I-10, 3 bridges on the SR-118, 2 bridges on the I5 and  2 bridges on I5/I14 interchange collapsed.  22,000 people were left homeless.

No doubt a major catastrophe. But one, according to Dr. Jones, that may  be exceeded by a projected Magnitude 7.8 striking in the Salton Sea between the two Coachella faults.

But my  real concern involves a large number of "moment steel frame (high-rise) buildings" which suffered large and unexpected cracks. 

From an article written by Greg Brower which appeared in the 1994 LA WEEKLY NEWS...

"When the Northridge quake awakened Los Angeles on January 17, 1994,  it was considered at 6.7 magnitude a relatively moderate shudder. However, because of its location, it was the first true seismic test for many of L.A.'s 1,500 steel-frame buildings. At first glance, most edifices seemed to fare well, but a disturbing trend soon surfaced: Many of the interior beam-to-column connections had cracked, in some cases splitting all the way through. The problem first came to light in structures still under construction, like the Getty Center, which was then just completing steel framing. Engineers there found a series of cracked connections and decided to replace all of its original welds. Owners of completed steel-frame buildings thus learned of the threat, but determining the status of their own welds would require breaking through plaster or concrete just to get a look. Still, the damage had been done -- the long-standing myth of the seismic invincibility of steel has been questioned ever since."

Was there something about the construction of certain steel buildings that caused problems. You bet.

The cracked connections in the steel structures, known as "welded steel moment frame"  (WSMF) buildings seemed to have a single factor in common, up to 99% of the connections were all welded with a particular welding method and using a particular welding material which had been previously approved for the use under the city's rigorous building code. However, as subsequent events demonstrated, the welding material and the process were inadequate to survive a moderate earthquake. Perhaps the capabilities and the performance of the welding method and materials were oversold by welding vendors who had no experience with seismic properties of the goods that they were selling as being a cost effective construction technique.

Even after noting the cracked connections, there was additional controversy over who would pay for the repairs and even what constituted  a safe practice of repair and replacement.

Again quoting from the 1994 article...

"There is no common definition or repairable damage vs. damage that requires retrofit strengthening. The decision varies from engineering office to engineering office. There appears to be no real guidance from either the building department in the local community, the engineering profession, or the welding society on this matter. (Similar significant ramifications are implied in future earthquakes if ductile flange buckling and yielding develops in the moment resisting frames due to seismic overload. When should the connection be repaired to compensate for damaging plastic distortions or replaced to restore the structure its original elastic strength?) Guidelines and standards are needed by the engineers to identify the acceptable level and extent of damage before repair procedures are converted to retrofit strengthening. "

"Engineers have proceeded with repair and retrofit strengthening based on judgment and common sense. They feel they are operating on their own, without specific guidelines as to scope of required repair and/or retrofit and without sufficient test data to substantiate the repair and/or retrofit schemes that they are using."

"The repair schemes typically consist of putting back a welded joint that more closely conforms to what the engineers thought they were specifying in the first place. Retrofit strengthening generally consists of adding plates or tees to the bottom and top flanges of the beam at the column joint to increase the connection capacity. There is little attempt to balance the design out by adding similar stiffness and strength to the undamaged connections of the WSMF. However, there is widespread concern is the engineering community that such an unbalance in stiffness and strength could result in less favorable performance in future earthquakes."

"Few owners are going beyond the simple repair process (i.e., putting the damaged connection back as it was before the Northridge earthquake). Only where FEMA or some other agency is picking up the cost of repair and retrofit are the owners requesting seismic upgrade. Repair costs for damaged connections in typical commercial buildings range from $3,000 to $20,000 per connection. The typical costs are in the $5,000 to $8,000 range. If asbestos has to be removed, the costs may increase by an additional $2,000 to $3,000 per connection. The owner's hidden costs associated with tenant expenses an lost rent may range from $0 to $45,000 per connection. Costs for retrofit strengthening may be comparable to those for repair in typical commercial construction. In residential and institutional construction, these costs may double or triple to $15,000 to $30,000 per connection for construction and $15,000 to $60,000 per connection for owner hidden costs if lost rental income is included."

While the building code has been changed and the methods and materials which appear to be the proximate cause of the cracking in Welded Steel Moment Frame (WSMF) construction have been long discontinued, questions remain:

Was a full inspection of all WSMF buildings, including those in the downtown area, Wilshire Boulevard Corridor and West Los Angeles area performed or were areas eliminated from inspection based on political rather than engineering concerns?

Does the Los Angeles Department of Building and Safety have an up-t0-date inventory of all WSMF buildings, their inspection records, post repair and retrofit inspection records and an indication of how many unexamined and/or un-repaired welded connections still exist?

Are the owners/operators or such WSMF building required to inform the tenants and occupants of the building's earthquake status?

Is there any reasonable coordinated modeling program being undertaken to determine if these WSMF buildings or any other buildings will survive a major quake in the Los Angeles basin or one in the surrounding "threat areas such as the aforementioned Coachella Valley?"

These are not idle questions, they are a matter of life and death to potentially thousands of occupants that spend much of their waking hours in high-rise buildings.

A call to the Los Angeles Department of Building and Safety was met with some talk about Homeland Security concerns, building inventories and internal structure questions ... hence I ask these questions openly before re-contacting the Department.

But the question remains,  is it possible that only the obviously damaged joints were replaced or repaired -- and the rest have remained untouched?  Silently waiting for another large quake to trigger a sequence of weld failures that could result in the deadly collapse of  large hi-rise buildings.

I want to know the answer ... as do the people who work in these buildings.

What can YOU do?

If you work in a high-rise, ask the building's management if the building suffered any damage in the Northridge quake and if the building had been retrofitted to the latest earthquake standards.

Ask the same question of the city's department of building and safety. Ask them about the disposition of welds that were judged to be acceptable on a visible basis and were not subjected to any further ultrasonic or other approved testing to determine their viability during a moderate to severe quake.

Ask departmental personnel about the quake modeling that is being conducted by the California Institute of Technology and other local schools. Specifically, if the findings in these scientific studies and theoretical models are being recognized by the department as legitimate planning tools for future performance prediction and preparation of  buildings for the quake that will surely come: probably sooner than later.

To see quake activity in the Los Angeles and surrounding areas, you may want to visit the USGS's excellent earthquake reporting site for quake maps and lists.

As always, it is extremely prudent to prepare a disaster plan for your  home, your office and for times when you may be traveling on California's scenic and not so scenic highways and byways.

For those interested in the subject of welding and seismic safety, I strongly recommend that you visit Ed  Craig's top-notch site, weldreality.com.

-- steve

A reminder from OneCitizenSpeaking.com: a large improvement can result from a small change…

The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane. -- Marcus Aurelius

References:

Quake Damage Statistics

Lucy Jones Meeting Coverage|Los Angeles Times - Scientist makes dire earthquake prediction: A major earthquake in the Coachella Valley is long overdue, she says, and her research foresees 'a whole new level of disaster.'

"L.A Buildings - Earthquakes - Human Tragedy and Bad Flux Cored Welds"|Ed Craig's Weld Reality.com

Scary reports from early years after the Northridge quake are routinely available. Is is the later reports showing inspection and mitigation summaries that are next to impossible to obtain.

"Between late January and early March of 1995, Durkin and Associates performed a regional survey to estimate the prevalence of steel frame building structural inspection, damage and repair in regions where the peak ground acceleration exceeded 0.20 g. A total of 163 buildings were selected at random from a list of 1284 candidate buildings. A standardized questionnaire was used in the collection of data via telephone interviews with the building owner, manager and/or engineer, The data collected was then analyzed and evaluated. Location information was provided for use in regional mapping efforts. The survey indicated that eighty-three per cent of the buildings had visual inspections performed, but only thirty-eight per cent had intrusive inspections, and only eighteen per cent included ultrasonic testing as part of the inspection. While only thirteen per cent of the buildings reported having steel connection damage, such damage was found in sixty-six per cent of the buildings that had ultrasonic inspection of a number of connections. Steel frame damage was concentrated in buildings between 200,000 and 300,000 square feet in area, less than five stories or between eleven and twenty stories in height, and constructed in the 1980's. The majority of the damaged buildings in the survey were located in San Fernando Valley or Santa Monica. A relatively high proportion of the damaged in the San Fernando Valley buildings were exposed to peak ground accelerations estimated to between 0.25 g and 0.35 g and peak velocities of 20 to 35 cm/sec. Repair work had been completed in over half of the damaged buildings at the time of the survey, and work was in progress in the remaining structures. While uncertainties over proposed inspection ordinances delayed in-depth inspections, other external forces such as lenders, insurers and out-of-state owners sometimes required such investigations."

Executive Summary - SAC 95-06  Surveys and Assessment of Damage to Buildings Affected by the Northridge Earthquake of January 17, 1994, by D. Bonowitz, M. Durkin, W. Gates, M. Morden, and N. Youssef, December, 1995.

California Institute of Technology continues to probe the problem using computerized modeling techniques. The sample project described here involves a quake from the north rather than the south as would be the case if the San Andreas/San Jacinto faults were involved.

Performance of 18-Story Steel Momentframe Buildings during a large San Andreas Earthquake - A Southern California-Wide End-to-End Simulation

From the results... (not in context)

As the rupture proceeds down south from Parkfield and hits the big bend on the San Andreas fault, it sheds off a significant amount of energy into the San Fernando valley, generating large amplitude ground motion there. A good portion of this energy spills over into the Los Angeles basin with many cities along the coast such as Santa Monica and Seal Beach and more inland areas going east from Seal beach towards Anaheim experiencing long-duration shaking.

As expected, the existing building model fares much worse than the redesigned building model. Fracture occurs in at least 25% of the connections in this building when located in the San Fernando valley. About 10% of connections fracture in the building when located in downtown Los Angeles and the mid-Wilshire district (Beverly Hills), while the numbers are about 20% when it is located in Santa Monica, west Los Angeles, Inglewood , Alhambra, Baldwin Park, La Puente, Downey, Norwalk, Brea, Fullerton, Anaheim and Seal Beach.


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