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Posted by Chuck News on March 12, 2008, 3:07 am
>
>>
>>>
>>>>
>> [Edited]
>>
>>>> As far as earthquake stuff goes, my knowledge is
>>>>> limited to general science stuff I've seen on the toob but I believe
>>>>> flexibility is the key.
>>>>
>>>> Felxibility, yup, that does seem to be a main, or poss. *the* main,
>>>> point. I saw one thing (let's face it, if thre is somehting on about
>>>> earthquakes, i watch it...) which showed buildings in Turkey - new
>>>> houses that were monolithing construction (cinderblock) fell apart,
>>>> btu traditional houses, which started with timber frames taht
>>>> included diagonal supports (not so differnt from old ENglish
>>>> half-timber methods), which then were filled in with bricks, remained
>>>> standing, with only a rew exceptions.
>>>>
>>>> Your point re: the trusses is also a good one. So, yup, it seems
>>>> that a building has to be a *system* to survive unusual conditions,
>>>> as opposed to merely being a collection of disparate parts...
>>>>
>>>> Let's hear it for cells (as in the biological/living things) ;)
>>>>
>>>> Actually, only half a joke - are you catching any of the new series
>>>> about the Body?
>>>
>>> No, but I'm going to.
>>> (short story: My wife and I have gotten into the habit of watching
>>> that show, 'How It's Made' on Discovery while eating supper and
>>> invariably they'll show a commercial about 'The Body' and eveytime
>>> they do I say, 'One of these days I'm gonna watch that show'. Its sort
>>> of a joke. So far I haven't watched it. We don't watch much.)
>>
>> Both are intresting, although sometimes the "how it's made" topics are
>> less interesting to me than teh biology-related things - such as, I
>> wasn't fascinated with how pencil erasers are made ;) Mechanical topics
>> are interesting, tho'.
>>
>>>> Last week, they discussed bones, and the high degree to which
>>>> bones are cellular is structure (as opposed tosolid) and *flexible* -
>>>> it was maazing to see how far a bone could bend before failing
>>>> (breaking). Biology has had millions of years to "experiment" and
>>>> offers intersting examples. Makes me wonder whether,a t some point,
>>>> we'll be able to *grow* buildings - although that's an entirely
>>>> different topic.
>>>
>>> According to Per Corel that exactly how its going to happen, sort of.
>>> He envisions his 3DH buildings constructed at the molecular level by
>>> microscopic robots and after a building is completed the robots will
>>> be reprogrammed to perform constant maintenance.
>>
>> THe problem is that I never could get a handle on what "3DH" actually
>> *means*. I also never caught the bit about the mini-robots, either, so
>> thanks for pointing that out... I had a hard time understanding the
>> explanations. I looked at the pics of models, but i guess I didn't get
>> out of them what was intended...
>>
>> Anyway, re: "grow buildings", I mean, biologically, not using robots.
>> More along the lines of breeding a tree, for example, that stays under a
>> certan height, and grows in a way that creates hollow chambers. Not even
>> my own idea, really, but somehting I came across in a "scifi" novel.
>>
>>
>>>> Meanwhile, the interactions between materials, and structures, and
>>>> the resulting resistance to stresses, is an interesting thing. I'm
>>>> thinking that the "weaklink" in wooden structures, as far as
>>>> earthquake resistance goes, might be the nails, since wood itself
>>>> seems far superior. SO I'm wondering whether it'd be "sturdier" (to
>>>> use the term a bit inaccurately but hopefully the meaning is clear)
>>>> to use fitted joints, as were used in the "pre-nails" days...?
>>>
>>> Here's a prediction, which I originally predicted some 10 years ago.
>>> Under the right conditions the wood trusses will fail because the
>>> number of nails required will effect the stability of it.
>>
>> Not surprising - the strength and flexibility of wood, like that of bone,
>> is not a funciton merely of the existence of verious types of cells and
>> "biological glue" so to speak, it's a funciton of the
>> *interconnectedness* of the cells and any other materials. THink abotu
>> the qualities of cartelege, and then think what would happen if it were
>> punched full of holes. People think of wood as "hard", more than they
>> think of it as "flexible", and same is true of bone. But part of the
>> strength *is* the flexibility, and that flexibility is comprimised once
>> the material is made discontiguous so to speak.
>>
>>> Right now, something like 18 nails are *required* at each
>>> truss/hurricane anchor and to me that many holes in the wood isn't a
>>> good thing. Ever seen a piece of wood with 18 nails in close
>>> proximity? It ain't pretty - the wood is horribly splintered.
>>
>> Yes, and true.
>>
>>> I'd rather see 12 guage angle steel reheaded into the top/side of the
>>> concrete tiebeam and through bolted through the truss heels - the
>>> angle steel would go up and over the top chord and be bolted from both
>>> sides. This would be less strain on the wood in the truss. The plywood
>>> roof sheathing, not OSB, 3/4" plywood, would be installed with #12 x
>>> 3" screws @ 8" o/c along the perimeters of the sheets and all plywood
>>> seams would receive 2x4 deadwood. These things would add about 15-20%
>>> to the cost of the roof but would add considerably to the overall
>>> integrity of it. **No inspector is ever going to count all the nails
>>> in every hurricane anchor on every house.
>>
>> Hmm. Interesting idea. I'm saving that one.
>>
>> ((Isn't the largest cost of most houses actually the land, rather than
>> the structure...?))
>
> Probably the most expensive single piece of land I've been involved with
> was $850k for less than 1/4 acre on Useppa Island and the house that was
> built on it was valued at over $2 mil.
> Most of the stuff I've done was a far less ratio.
> My own property in the Cape cost $3500 in 2001 for 1/4 acre and in 2006 I
> sold it with a house on it for $300k and the original cost of the house
> was $155k + add-ons.
>
The word that you are looking for is Ductility not flexibility. Such as a
ductile moment frame. Hope this answers the question.
CID...
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