Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Tangshen

[Subject Prev][Subject Next][Thread Prev][Thread Next]
To Frank -
In one respect, the comparison is justified. It took almost fifty years for
the State of California to adopt a Hazard Mitigation Law that would go back
and retrofit all the URM's constructed prior to 1933. If we knew from the
Long Beach Earthquake that URM's are unsafe, why did it take 50 years to
improve their performance?
In 1992 (or there about)California passed Assembly Bill 200 (Frank you
remember the Triple R committee). AB200 identified that over 1.3 million
single family homes in California constructed before 1969 may have
structural deficiencies related to cripplewall failures or improper
anchorage to their foundations. Why did this become a law when so few lives
were lost in single family homes.

One bigger questions: In addition to the 1.3 million SFR with structural
defects, there are many thousands of multi-residential apartment buildings
and condo's that have the same deficiency. Why were these buildings
purposely omitted from the rhetoric of AB200? I have inspected these
buildings in Los Angeles - they do exist and are a greater risk. BTW, wasn't
Northridge Meadows one of the types of cripple wall structures? It is my
belief that they are omitted because of the lobby power of Apartment
building owners who have their own coalition. I also understand that it was
necessary to omit these buildings in order to pass AB200.
Still, thousands of lives are endangered because of the power of the
Building Owner in state politics.

Conversely, single family URM structures are omitted from compliance with
the State Hazard Mitigation codes - why? It is not a state requirement to
force compliance of a SFR even if it is known to be constructed of
unreinforced masonry or adobe. The answer is both statistical and political.
In either case, those with the most money can easily defeat those without.

Even when life safety is the issue, codes are stonewalled from reaching
fruition because of the financial power coming from stronger lobbyist. Once
again, money rules over those without - even in life safety issues.

Dennis
-----Original Message-----
From: John Nichols [mailto:cejn(--nospam--at)engmail.newcastle.edu.au]
Sent: Sunday, May 24, 1998 8:07 PM
To: seaoc(--nospam--at)seaoc.org
Subject: Re: Tangshen


Dear Frank Lew,

Considering I eat an orange and apple for lunch each day; you might just be
right.  Let me clarify my comments a bit.  Firstly the statisitcs I refer to
come from Shiona, K., Japanese Society of Civil Engineers "Interpretation of
published data of the 1976 Tangshen, China earthquake for the determination
of a falality rate function. V11 No 4 155s-163s Jan 1995


In the mail I read this morning was the comment

"that only a small fraction of all homes in
the Bay Area will be uninhabitable. There are roughly 5 million people in
1.7
million housing units in the Bay Area. A 150,000 loss is about 9 percent of
the housing stock for the entire Bay Area - comparable to that 8 percent
lost
in Watsonville in the Loma Prieta Earthquake. In the East Bay alone, the
percent loss may be as high as 10 to 20 percent . Assuming 2.5 persons per
household, that could be 375,000 homeless. "

Based on the Tangshen data at a 9 percent housing stock loss then one would
estimate would cause upto a 2 percent death rate in an Intensity 8 (MM Scale
Event).  The Newcastle earthquake at 5.5 M generated 8 in alluvial areas
killing 13 in an engineer designed structure and from falling masonry.

At a 20 percent loss in both Timber and Masonry buildings would cause a 5
percent death rate.  In the peak areas you are looking at upto 25 percent.
The Chinese engineering

In the latest National Geographic that I read last night in bed it provides
a description of a M9 earthquake in the north west area (Oregon ?) in the
last few hundred years.  I canna remember exact position or date, I will
look it up tonight.  (It is the first M9 I had read about and I wondered if
it was a mistake.  But accepting that the NG make very few mistakes i will
accept it for the moment)

A M9 is total destruction and one could expect the Tangshen death rate at
the centre 30percent.

I am concerned not with past but the future.  I accept that the provision of
code deemed to comply houses is a step accepted by the community.  That does
not mean that I accept that all its provisions are good ideas.  My timber
framed house built to a deemed to comply standard has been through two
earthquakes one at 5.5 and a southerly to about 100 mph.  Faces due south
CAtegery 1 exposure on top of a bluff,  could get worse I suppose.  The
house has many defects in its construction yet it was built by a large
British firm who employed engineers.  It was a stock standard design.

I also accept that engineers allow masonry of interesting qualities and many
other such problems.

I accept that I sometimes move out of the thread in this case there are two
or three threads running that are talking about professional standards.

But my personal opinion for what its worth is that more care should be taken
in the supervison of construction of houses, whether it is deemed to comply
or not or engineer designed.  For the reason that in an event that requires
this capacity it might just save a few lives maybe a few thousand.  Then
again is the investment worth it, at the moment I would say that the
community does not think so.  Even the engineering community is divided.

If you are going to flame me again fell free but could it wait till tomorow
casue I am trying to get a paper out to teh British masonry society Journal
and I enjoy doing this more.

LOL

John Nichols


At 21:40 24/05/98 -0400, you wrote:
>Dear John Nichols,
>
>You are comparing oranges and apples.  There's no argument that earthquakes
>have taken horrific tolls of lives, particularly in those regions where
>unreinforced masonry construction is the norm.  But from what I know about
the
>Tangshan earthquake, and I've read extensively on the event, none of the
>242,000 deaths were reported to have occurred in **single family detached
>wood-framed houses built according to the conventional construction
provisions
>in the model codes used in the U.S**  And it is this category of building
that
>is the subject of this thread.  For such buildings, the cumulative body
count
>in the U.S., going back to 1776, is very low, likely less than 10.
>
>Since I'm now in the gunsights of many folks who feel I'm spouting heresy,
>here's another thought to start more howling.   Most of the deaths in
>residential structures in the Northridge event were in buildings that were
>required by the State of California to be, and thus were, designed by
licensed
>professionals.  Furthermore, those buildings were plan checked and
inspected
>by a building department whose staff could arguably content is the most
>competent building department extant.   By this comment, I am not knocking
>that department, but merely to point out that wood-frame buildings designed
>and checked by professionals to comply with the codes, and adequately
>inspected, nevertheless have killed many more people than buildings that
>'only' met conventional construction.
>
>Frank Lew, SE
>Orinda, CA
>
>In a message dated 98-05-24 20:38:22 EDT, cejn(--nospam--at)engmail.newcastle.edu.au
write
>
>> The death rate from the Tashkent earthquake in the centre 47 sq
kilomrtes,
>> about 20 sq miles was 1 in 3.  Look at your family of say 5 kids grand
>> children etc and subtract off 30 percent.  Poorly constructed masonry can
>> survive an earthquake seen it plenty.  It is plain dumb luck that it was
>> built in right place so not get a full load or its on rock.
>
>< The problem with masonry is it very rapidly climbs as a killer in
>> earthquakes.  Of course they only lost 256,000 in Tashkent.
>
>> I refer you to JSCE  V0l 11 No 4 p 155s-163s and also to the latest
National
>> geopgraphic on the earthquakes in the pacific northwest.
>
>> Of course your right your chances of dying in an earthquake are remote
>> unless your in the wrong place at teh wrong time.  Then the odds are
>appalling.
>
>In a message dated 98-05-24 20:38:22 EDT, cejn(--nospam--at)engmail.newcastle.edu.au
write:
>
>>  I dinna know why i keep thinking of it as Tashkent.  But i was wrong and
>>  only 242,000 died.
>>
>
>
>
>