Earthquake!!

[slodave]

Originally Posted by dd74

...and I was joking. There are no viable warnings. If there were, Caltech would recommend the "warning" to everyone.

You truly don't know if you will live or die in one of these things.

And I'm just a little ticked off at all the California bashing at the moment (and my keyboard).

No fish tank movement here either and they'e not secured.

[dd74]

Originally Posted by Hugh R

...but didn't have quake insurance, big mistake then, lots of people made big money on that. Have the state quake insurance now, which probably won't cough up much, but I have it.

No, lots of people made money on house bolting. That's the biggest sham there is. Guaranteed to rip your house in halves if you bolt your foundation.

[dd74]

Originally Posted by slodave

And I'm just a little ticked off at all the California bashing at the moment...

You know they all want to be out here. Or if they left, they want to return.

What's ticking me off is the non-stop "Quake" coverage on the news channels. All right already!

[JeremyD]

Hey no bashing here - I loved the weather - I loved the diversity - I loved the topography. I loved the food and the culture. The water is too cold for me, the traffic was off the hook, I didn't like giving my first 9% to the state. It just scared the crap out of me when we had the quakes - I'm more of a control guy - tornados where the same way - Bam and there goes your trailer.

Pulled off MSNBC "Earlier this year, scientists calculated that California faces a 99.7 percent chance of a magnitude-6.7 quake or larger in the next 30 years. "

There is a lot of stuff wrong with Florida - but good things too - and after living in 22 different places - there are good and bad things about everywhere...

[looneybin]

Originally Posted by dd74

No, lots of people made money on house bolting. That's the biggest sham there is. Guaranteed to rip your house in halves if you bolt your foundation.

What????? The best protection you can do for your structure is to bolt it to the foundation, otherwise it could bounce off, then you ARE toast.

[TerryH]

First thing insurance inspectors check is if the older home is bolted to foundation. It's a must.

Earthquake insurance was actually affordable when it was first offered. Now it can be more than a standard policy and the deductibles are huge. On a $500,000 policy, the deductible can be $100,000. If one wall collapses on my home, I may as well knock the others down so the insurance can kick in.

Hugh, quake insurance wouldn't have helped you with your fireplaces. You need almost catastrophic damage.

[Zeke]

Originally Posted by dd74

No, lots of people made money on house bolting. That's the biggest sham there is. Guaranteed to rip your house in halves if you bolt your foundation.

I think you are a bit misinformed. But, if you cite your sources, I'll read.

However, if the job is not engineered and executed properly, I agree that one could possibly make matters worse in a unique combination of misguided installations of seismic attachments.

Actually, I could go into that business and feel good about myself. But, again, I do very good and conscientious work at whatever I do.

[aigel]

Sometimes I wonder if those scientists are very objective. Predicting earthquakes seems like long term weather forecast. You have to pick a model and make assumptions. Are they going to pick the ones that result in non-dramatic predictions? That's not how you get funding for your work ...

George

[onewhippedpuppy]

Seriously, if you predict there will be a large earthquake in SoCal in the next 30 years, aren't the odds on your side? Hell, he'll probably retired before 30 years are up, and won't even care. Get it down to the day, then I'll be impressed.

[dd74]

Originally Posted by milt

I think you are a bit misinformed. But, if you cite your sources, I'll read.

However, if the job is not engineered and executed properly, I agree that one could possibly make matters worse in a unique combination of misguided installations of seismic attachments.

Actually, I could go into that business and feel good about myself. But, again, I do very good and conscientious work at whatever I do.

I looked around briefly and found this from RePEc:

In general, the survey results can be summarized as follows. First, the use of the MMI scales was not well received by the engineers, who are more familiar with the Richter scale or measure of peak ground acceleration. Second the importance of quality of construction, the weight and shear capacity of the structure above ground, and non-structural damage should not be underestimated. Third, existing conditions such as rot and termite damage can greatly effect costs and effectiveness. Fourth, survey damage values were less that comparable values found in the "ATC-13" and FEMA 227/228 guidelines. Finally, there was wide variation in both damage and cost estimates in both survey groups."

Nowhere in here does it state that bolting is beneficial. In fact, this suggests building material and house weight are instrumental in keeping a house on its foundation. Any other information I found which shows the benefits of bolting is provided by companies who provide bolting services - i.e. just one long advertisement for their services.

After Northridge, several suggested we bolt down our house. We had independent structural engineers come by and state a house is supposed to be a bit fluid with its foundation, not stand rigid against it by bolting. They said, essentially, that bolting could cause more structural damage to a home during an earthquake, than if it were not bolted.

[Zeke]

Well, we could digress into another subject here. Speaking of "subject," this topic of seismic bolting is subjective. As I said, a bad job is tantamount to no job at all. It all depends on the structure being considered. Many SoCal homes are built on a cripple wall, raised floor design. just bolting such a design w/o shear paneling the cripple portion would be bassackwards. FWIW, the stucco is all that's holding these houses in place. Once the force hits enough magnitude that the stucco begins to break, the house is going to fall down in areas or move off the foundation. A home constructed of all wood is more "fluid" as you say. Perhaps making one portion too rigid as opposed to the rest would cause the house to react in 2 different ways tearing it apart. The Northridge event produced solid evidence that short nailing and other short cuts taken during the framing stage made fro very dangerous structures. The bigger and crappier they were, they fell down.

Having just built a large addition to a very large home in Westwood, I'm up to speed on what the City of LA is looking for in retrofit and new construction. I can only say this: you are in disagreement with the entire structural engineering community, at least the many that I dealt with.

Anyway, the case is usually that a quake relieves pressure at the fault(s) and we won't have to worry for awhile now.

[Zeke]

" * Similarly, there are two ways in which a seismic retrofit can be designed for light wood frame houses.
1. The owner or contractor could hire an architect or an engineer to design the retrofit. There are many houses that have complications that will require an engineer or architect to design the retrofit.

2. Another way to retrofit a house is to use a prescriptive standard. How do we know that the prescriptive standards work?

* Example: In a neighborhood of bungalow houses, a single 1920s bungalow house had been retrofitted prior to the Northridge Earthquake. After the quake, it was the only house left standing; the only damage was a fallen chimney.
* Remember that houses retrofitted incorrectly can be damaged just as much as those that were not retrofitted at all."

source: http://www.abag.ca.gov/bayarea/eqmaps/fixit/ch1/tsld009.htm

[dd74]

Originally Posted by milt

...Westwood

Where I grew up, and where many houses are not bolted, and which have not fallen or slid their foundation from Sylmar, Northridge or any other big quake.

Originally Posted by milt

I'm up to speed on what the City of LA is looking for in retrofit and new construction.

...and who advises the City of L.A. about this? What's their stake in this market?

Originally Posted by milt

I can only say this: you are in disagreement with the entire structural engineering community, at least the many that I dealt with.

And who is this engineering community? Again, some readable sources would be handy. As you know, many shams travel about L.A. Mold experts, earthquake retrofitters, house bolting. I want credible evidence and credible companies. Not pickup trucks that have "Earthquake Bolting" plastered on their doors beside "Gardening Services Provided."

Originally Posted by milt

Anyway, the case is usually that a quake relieves pressure at the fault(s) and we won't have to worry for awhile now.

That's not a proven fact. In some cases, more pressure is applied to the fault or other faults. It would take a lot of little quakes to relieve a large amount of pressure.

[dd74]

Originally Posted by milt

" * Similarly, there are two ways in which a seismic retrofit can be designed for light wood frame houses.
1. The owner or contractor could hire an architect or an engineer to design the retrofit. There are many houses that have complications that will require an engineer or architect to design the retrofit.

2. Another way to retrofit a house is to use a prescriptive standard. How do we know that the prescriptive standards work?

* Example: In a neighborhood of bungalow houses, a single 1920s bungalow house had been retrofitted prior to the Northridge Earthquake. After the quake, it was the only house left standing; the only damage was a fallen chimney.
* Remember that houses retrofitted incorrectly can be damaged just as much as those that were not retrofitted at all."

source: http://www.abag.ca.gov/bayarea/eqmaps/fixit/ch1/tsld009.htm

Interesting, but not convincing. During Northridge, I was in a neighborhood of 1920s Bungalow houses. Not a single one slid from its foundation, nor collapsed.

[dd74]

Can this keep a house on its land during a 7+ earthquake? A lot depends on how close the house is to the epicenter, the type of shaking, the quality of the beams, etc.


This is used when a house is taller than it is wider. Designed to not allow the house to tip over. However, I can see where the house, particularly if its wood framed, could snap in half.

All I'm saying is bolting isn't definitive, and should not be stated by these companies as a live or die scenario to a home owner. Besides which, the $-to-rip off potential is huge. The USGS suggests bolting should cost $1,000 per a normal-sized house - probably 2,500 square feet. I've seen quotes of $5,000 - $10,000.

[Zeke]

Originally Posted by dd74

And who is this engineering community? Again, some readable sources would be handy. As you know, many shams travel about L.A. Mold experts, earthquake retrofitters, house bolting. I want credible evidence and credible companies. Not pickup trucks that have "Earthquake Bolting" plastered on their doors beside "Gardening Services Provided."

Wow, you have dim view on all this. Hey, I'm as critical of shams as anyone and my posts here reflect that.

OK, I'll try to answer the only part of this that will benefit anyone. The plans spent the better part of a year in the city offices. I suppose maybe only 1 or 2 different city engineers looked them over each time they were submitted and resubmitted for corrections. The city inspector overrode all the specs anyway, as any inspector can do. I can't give you readable sources other than the plans themselves.

The first engineer (I'm not going to name these folks because I do not have their permission) did the work on the existing house. This was a major feat in itself costing about 75K to level the house and place new footings as necessary. The chimney was bolted back to the roof and the living room ceiling reworked as it was sagging. New basement walls as well and almost a complete new garage (the four exterior walls were left because of property line location) including floor, ceiling and roof.

Another civil engineer did the plans for the new part and he was a PITA. I came close to knocking out his lights one day when he came by and discovered there was no footing where he had calculated on one being there. This was one of 6 changes that added about 20K to the original cost.

So, just on this job, I experienced the inside city engineers for the jacking and the new addition.I dealt with the two civil cats plus the inspector. That was a minimum of five people telling us what to do next as they discovered the errors.

Now, each time there was a change, the new set of calcs went to the city. It would be silly to think each time the same person stamped them. The only people that remained constant in presence were the city inspector and the project civil, who was brought in by the architect. BTW, neither of them knew what they were doing. What we ended up with was a far cry from what was drawn on the plans. At one point, they lost and entire 10 inches of wall. Just wasn't there to begin with, so nothing fit.

All in all, the plans were resubmitted for changes about a dozen times split between before the work began and after. We spent over 4K in Simpson hardware alone. We used over 40 sheets of struct 1 1/2" ply for shear. We used over 100 linear feet of all thread in 3/4" but mostly 7/8ths. I can't tell you how many 100's of feet of rebar went in the concrete, but there was 10 yards of it placed for a footprint of 200 sq. feet! We put in about 30 of the HD's you show, several of them upside down under the second floor connected to ones above. Talk about overbuild, this was it. But, that's what's going down at the city. Most local jurisdictions are following LA's lead.