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Invisible wrote:
> PS. Don't you ever hit a point where it's not possible to design for 2x
> the maximum? Or do you just decide not to build the thing at all at this
> point?
It depends what you're building. Fighter jet? No. Passenger airplane?
Yes. Skyscraper? Don't build it. Space station? Go for it.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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> It depends what you're building.
I see...
> Fighter jet? No. Passenger airplane? Yes.
Hmm. That's deep.
> Skyscraper? Don't build it. Space station? Go for it.
LOL!
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> True.
>
> OTOH, if you've expecting a maximum wave hight of X, you design to
> withstand 2X, and then suddenly a 12X have hits... hmm, Not Good(tm).
It's impossible to design anything to be 100% sure of lasting a set time
when it's being attacked by an essentially random force. That's why you
have models and can choose a chance of it being broken in its lifetime, eg
0.1% over 10 years. Of course that means there's a 0.1% chance of a >2X
wave coming along in 10 years, but what else can you do?
> PS. Don't you ever hit a point where it's not possible to design for 2x
> the maximum?
It's never impossible, just sometimes too costly or not practical. Then you
might do some more detailed simulations to bring the 2X figure down to 1.5X
or something with a suitable level of confidence. Or just think up a
different way to solve the problem. Usually it comes down to cost though.
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>> OTOH, if you've expecting a maximum wave hight of X, you design to
>> withstand 2X, and then suddenly a 12X have hits... hmm, Not Good(tm).
>
> It's impossible to design anything to be 100% sure of lasting a set time
> when it's being attacked by an essentially random force. That's why you
> have models and can choose a chance of it being broken in its lifetime,
> eg 0.1% over 10 years. Of course that means there's a 0.1% chance of a
> >2X wave coming along in 10 years, but what else can you do?
My point being "what happens if the model says force X is the largest
that's ever likely to occur, but it turns out the model is wrong and
actually force 12X is fairly common"... Presumably that's a pretty bad
thing?
>> PS. Don't you ever hit a point where it's not possible to design for
>> 2x the maximum?
>
> It's never impossible, just sometimes too costly or not practical. Then
> you might do some more detailed simulations to bring the 2X figure down
> to 1.5X or something with a suitable level of confidence. Or just think
> up a different way to solve the problem. Usually it comes down to cost
> though.
OK. Cool.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> My point being "what happens if the model says force X is the largest
> that's ever likely to occur, but it turns out the model is wrong and
> actually force 12X is fairly common"...
For most things there are "standard models" that are used, and have been
tried and tested for decades. You *must* use these, by law. Of course for
weird things that aren't covered in law, you are free to make your own
design decisions. If you design something to withstand X, and 12X is
"fairly common" you're going to be in *big* trouble when people are injured.
> Presumably that's a pretty bad thing?
Yes. You could end up responsible for lots of people dying and face the
consequences.
It's why we have such things as "Chartered Engineers", who have demonstrated
competence in industry and not just graduated from any old university with a
degree in structural Engineering. Most structural Engineering firms will
not employ any non-chartered Engineers to do anything important.
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OMG! One of the sheep designers is... Sylvie Gallet.
She's still out there...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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scott wrote:
>> My point being "what happens if the model says force X is the largest
>> that's ever likely to occur, but it turns out the model is wrong and
>> actually force 12X is fairly common"...
>
> For most things there are "standard models" that are used, and have been
> tried and tested for decades. You *must* use these, by law. Of course
> for weird things that aren't covered in law, you are free to make your
> own design decisions. If you design something to withstand X, and 12X
> is "fairly common" you're going to be in *big* trouble when people are
> injured.
>
>> Presumably that's a pretty bad thing?
>
> Yes. You could end up responsible for lots of people dying and face the
> consequences.
>
> It's why we have such things as "Chartered Engineers", who have
> demonstrated competence in industry and not just graduated from any old
> university with a degree in structural Engineering. Most structural
> Engineering firms will not employ any non-chartered Engineers to do
> anything important.
My point was that the standard wave model says that "12X happens once
every few millennia", but now it turns out that actually it happens
somewhere on Earth once every few weeks - and that's kind of worrying...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> My point was that the standard wave model says that "12X happens once
> every few millennia", but now it turns out that actually it happens
> somewhere on Earth once every few weeks - and that's kind of worrying...
Well sure, but I haven't yet heard of all the oil rigs and other off-shore
structures being reinforced due to fears of the model used 20 years ago
being incorrect by 3 orders of magnitude...
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On Tue, 15 Jan 2008 14:28:53 +0100, "scott" <sco### [at] laptop com> wrote:
>> My point was that the standard wave model says that "12X happens once
>> every few millennia", but now it turns out that actually it happens
>> somewhere on Earth once every few weeks - and that's kind of worrying...
>
>Well sure, but I haven't yet heard of all the oil rigs and other off-shore
>structures being reinforced due to fears of the model used 20 years ago
>being incorrect by 3 orders of magnitude...
>
From my knowledge of working on oil rigs and platforms. They were designed to
survive a 100 foot wave occasionally. Occasionally became every other year but
you are forgetting that in the summer when the weather is good, maintenance is
carried out and faults are repaired.
Regards
Stephen
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> I'd actually prefer to run it as a stand-alone application rather than a
> screen saver, but hey.
http://www.geocities.com/c00l_ac/SheepWatcher.html
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