Earthquake resistance: Linear, or not...? - Page 2

> 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?
> 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.

>> SO, if it's designed to withstand 150mph, and a 160mph wind occurs,

>> whole thing simply disintegrates instantly...?
>> What I'm trying to figure is, if people are in a bldg (house,

>> whatever) rates to withstand X.Y, but a quake of X.y+1 occurs, does

>> bldg just completely disintegrate/implode into shards at that point

>> kill everyone inside?
>> 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

>> onto rubber "floats" - I couldn't tell. But San Francisco (IIRC) has
>> been literally lifted and placed onto rubber plugs that are supposed
>> 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.
>
> You're asking a question that can't be answered simply. You'd design
> a building for 150 mph winds, but there are factors of safety
> involved. The probability that a failure will occur with a wind
> higher than the design load increases but it's not linear, it's not
> simple and it's often times not calculable. The only way to test it
> would be to overload it to destruction.

>
> There are localized conditions and unforeseeable benefits and
> disadvantages that help or hinder the chances of a buildings
> survival. The surrounding terrain could help or hurt, for instance.
> The design might have been based solely on nailed sheathing and the
> cowboy with the nailgun might have missed the studs with a bunch of
> nails. These things are not included in design calculations. A
> building might withstand a wind load 50 percent higher than the design
> load, or it might fail at or below the design load due to unaccounted
> for variables, faulty calculations and assumptions, or poor
> construction.
>
> So, I guess what I'm saying is make sure your insurance is paid
> up! ;)
>
> R
>

>

>> 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.)

>> 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.

>> 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.

> 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.

> 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.

>
>> [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.