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Posted by Kris Krieger on March 7, 2008, 10:46 pm
>
>>
>>> Kris Krieger wrote:
>>>> I was watching something about earthquakes and building (or
>>>> retrofitting) for earthquake resistance. I'm assuming it's a
>>>> "curved graph", but maybe not? So I was wondering, if something is
>>>> made to survive an earquake of X.Y , would it fail catstrophically
>>>> at X.Y+1, or would damage increased in a way that'd be mroe of a
>>>> cruved line of a graph...? I'd assuem teh latter, but what seems
>>>> logical, isn't always how things work.
>>>
>>> It doesn't work like that. The interactions involved are more
>>> complicated that the question assumes. FYI, the Richter scale is
>>> exponential:
>>>
>>> http://en.wikipedia.org/wiki/Richter_scale
>>>
>>
>> I know the Richter scale is exponential, but I'm still wondering
>> whether a structure builkt to withstand X.Y fails at X.Y+1. So, they
>> aer currently retrofitting the Golden Gate Bridge to withstand
>> soemthng like 8.3, but does that mean it will fail (i.e.
>> disintegrate) at 8.4, or what?
>
> Can't be done, except in a computer model, cause there's too many
> variables. First, you have to define *failure* then design around that
> parameter. In SW FL for example the homes I design are supposed to
> sustain a 130 to 150 mph wind and usually they do.
> But that doesn't mean things won't fail.
SO, if it's designed to withstand 150mph, and a 160mph wind occurs, the
whole thing simply disintegrates instantly...?
What I'm trying to figure is, if people are in a bldg (house, highrise,
whatever) rates to withstand X.Y, but a quake of X.y+1 occurs, does the
bldg just completely disintegrate/implode into shards at that point and
kill everyone inside?
> On my own house, it went through several hurricanes but some things
> did fail, though nothing structural.
> If any of those hurricanes would have stalled on my house there very
> well may have been structural failure.
> Some of the soffit tore loose, a design flaw (which was later
> corrected), that allowed wind to penetrate the envelope.
> If this wind would have sustained it may have lifted that portion of
> the roof and once that happens its all over.
> (I installed more, and longer, nails along the edge of the fascia that
> attaches the soffit and used 24 tubes of silicone caulk to secure the
> soffit to the stucco wall and fascia. This had the added benefit of
> thwarting the yellow jackets from nesting in the valleys of the
> soffit) Regarding the Golden Gate, what did they do, put it on pulleys
> so it'll sway like a pendelum?
I couldn't really teel from the program - in many areas, it looks like
they're reinforcing it, but I don't knw whether other areas might be put
onto rubber "floats" - I couldn't tell. But San Francisco (IIRC) has
been literally lifted and placed onto rubber plugs that are supposed to
absorb the shaking. THey also described the swaying that some wooden
houses can withstand.
So that's what all got me wondering about building for earthquake
resistance, and what the limits of that are.
I'm not sure I asked the question properly, either.
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