Cost to build Gerard K. O'Neill's "Island Three"

Derek Lyons wrote:
"John F. Eldredge" wrote:

I find the Pantheon in Rome particularly impressive. It has an
unreinforced concrete dome that has survived 2,000 years in an
earthquake zone. A lot of current-day concrete structures start
crumbling within a decade after being built.

And a lot more don't.


And of course we no longer have examples of all the Roman architecture that
didn't survive because it was poorly built.

It's a self-selecting observation. Like folks in Florida who talk about
homes not destroyed by hurricanes. "They don't build them like they used
to!" Yeah but you're only the seeing the ones that survived, not all the
ones that had previously been wiped out.
D.

--
Greg Moore
Ask me about lily, an RPI based CMC.

On Oct 1, 9:49*am, "Greg D. Moore \(Strider\)"
wrote:
Derek Lyons wrote:
"John F. Eldredge" wrote:

I find the Pantheon in Rome particularly impressive. *It has an
unreinforced concrete dome that has survived 2,000 years in an
earthquake zone. *A lot of current-day concrete structures start
crumbling within a decade after being built.

And a lot more don't.

And of course we no longer have examples of all the Roman architecture that
didn't survive because it was poorly built.

It's a self-selecting observation. *Like folks in Florida who talk about
homes not destroyed by hurricanes. "They don't build them like they used
to!" *Yeah but you're only the seeing the ones that survived, not all the
ones that *had previously been wiped out.

True, as far as it goes.

But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

In central Italy the recurrence rate of magnitude 7+ earthquakes is
700 years of so, so the Pantheon has survived ~3 or so. In particular
there was one in 1349 that severely damaged the Colosseum.

The interior of the building has been remodeled any number of times,
but the dome has stood without structural maintenance since its
construction in 128 CE.

In article
,
" wrote:

On Oct 1, 9:49*am, "Greg D. Moore \(Strider\)"
wrote:
Derek Lyons wrote:
"John F. Eldredge" wrote:

I find the Pantheon in Rome particularly impressive. *It has an
unreinforced concrete dome that has survived 2,000 years in an
earthquake zone. *A lot of current-day concrete structures start
crumbling within a decade after being built.

And a lot more don't.

And of course we no longer have examples of all the Roman architecture that
didn't survive because it was poorly built.

It's a self-selecting observation. *Like folks in Florida who talk about
homes not destroyed by hurricanes. "They don't build them like they used
to!" *Yeah but you're only the seeing the ones that survived, not all the
ones that *had previously been wiped out.

True, as far as it goes.

But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

Was it the only dome they tried to build like that, or did they do a
number of them and it's the only one left?

--
Chris Mack "If we show any weakness, the monsters will get cocky!"
'Invid Fan' - 'Yokai Monsters Along With Ghosts'

wrote:
On Oct 1, 9:49 am, "Greg D. Moore \(Strider\)"
wrote:
Derek Lyons wrote:
"John F. Eldredge" wrote:

I find the Pantheon in Rome particularly impressive. It has an
unreinforced concrete dome that has survived 2,000 years in an
earthquake zone. A lot of current-day concrete structures start
crumbling within a decade after being built.

And a lot more don't.

And of course we no longer have examples of all the Roman
architecture that didn't survive because it was poorly built.

It's a self-selecting observation. Like folks in Florida who talk
about homes not destroyed by hurricanes. "They don't build them like
they used to!" Yeah but you're only the seeing the ones that
survived, not all the ones that had previously been wiped out.

True, as far as it goes.

But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

There's no doubt it's an engineering marvel. But also keep in mind they
were building on previous experience, but successful and not so successful.
And there's a lot of stuff they "over-built" since they didn't know any
better.


In central Italy the recurrence rate of magnitude 7+ earthquakes is
700 years of so, so the Pantheon has survived ~3 or so. In particular
there was one in 1349 that severely damaged the Colosseum.

The interior of the building has been remodeled any number of times,
but the dome has stood without structural maintenance since its
construction in 128 CE.

--
Greg Moore
Ask me about lily, an RPI based CMC.

Greg D. Moore (Strider) wrote:
wrote:
On Oct 1, 9:49 am, "Greg D. Moore \(Strider\)"
wrote:
....
But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

There's no doubt it's an engineering marvel. But also keep in mind they
were building on previous experience, but successful and not so successful.

So that's like - everybody, everywhere, at all times, throughout all of
history, right? Is there any time in engineering history when this
generalization isn't true?

(I have several books on the role of failure in engineering history
collectively showing its ubiquity, by the way, so this really is just a
rhetorical question.)

And there's a lot of stuff they "over-built" since they didn't know any
better.

So you are saying they used sufficient margins of safety to account for
the uncertainties in their designs and materials? Egads, what outrageous
deviation from engineering practice!

Is the stuff that didn't fall down in 2000 years of seismic history
actually "over-built" while the stuff that collapsed "properly built"?

Are we saying then that the Pantheon is standing because "they didn't
know any better"?

I think your demurrals are straining at gnats.


In central Italy the recurrence rate of magnitude 7+ earthquakes is
700 years of so, so the Pantheon has survived ~3 or so. In particular
there was one in 1349 that severely damaged the Colosseum.

The interior of the building has been remodeled any number of times,
but the dome has stood without structural maintenance since its
construction in 128 CE.

" wrote:

On Oct 1, 9:49*am, "Greg D. Moore \(Strider\)"

And of course we no longer have examples of all the Roman architecture that
didn't survive because it was poorly built.

It's a self-selecting observation. *Like folks in Florida who talk about
homes not destroyed by hurricanes. "They don't build them like they used
to!" *Yeah but you're only the seeing the ones that survived, not all the
ones that *had previously been wiped out.

True, as far as it goes.

But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

The two statements are unconnected Carey, being an engineering marvel
is no guarantor of being a survivor. The Colliseum was an engineering
marvel, as was the Parthenon. Neither of them are looking too good
nowadays.

D.
--
Touch-twice life. Eat. Drink. Laugh.

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

Carey wrote:
Greg D. Moore (Strider) wrote:
wrote:
On Oct 1, 9:49 am, "Greg D. Moore \(Strider\)"
wrote:
...
But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

There's no doubt it's an engineering marvel. But also keep in mind
they were building on previous experience, but successful and not so
successful.

So that's like - everybody, everywhere, at all times, throughout all of
history, right? Is there any time in engineering history when this
generalization isn't true?

(I have several books on the role of failure in engineering history
collectively showing its ubiquity, by the way, so this really is just a
rhetorical question.)

And there's a lot of stuff they "over-built" since they didn't know
any better.

So you are saying they used sufficient margins of safety to account for
the uncertainties in their designs and materials? Egads, what outrageous
deviation from engineering practice!

Is the stuff that didn't fall down in 2000 years of seismic history
actually "over-built" while the stuff that collapsed "properly built"?

Are we saying then that the Pantheon is standing because "they didn't
know any better"?

Parthenon?


I think your demurrals are straining at gnats.


In central Italy the recurrence rate of magnitude 7+ earthquakes is
700 years of so, so the Pantheon has survived ~3 or so. In particular
there was one in 1349 that severely damaged the Colosseum.

The interior of the building has been remodeled any number of times,
but the dome has stood without structural maintenance since its
construction in 128 CE.

Carey wrote:
Greg D. Moore (Strider) wrote:
wrote:
On Oct 1, 9:49 am, "Greg D. Moore \(Strider\)"
wrote:
...
But are you suggesting that the world's largest unreinforced
concrete dome, and the world's largest dome of any kind before
1881, is still standing because it got lucky? That they could build
it at all is an engineering marvel.

There's no doubt it's an engineering marvel. But also keep in mind
they were building on previous experience, but successful and not so
successful.

So that's like - everybody, everywhere, at all times, throughout all
of history, right? Is there any time in engineering history when this
generalization isn't true?


It's pretty generally true. Though one could argue that places like Haiti
are the exception.

(I have several books on the role of failure in engineering history
collectively showing its ubiquity, by the way, so this really is just
a rhetorical question.)

And there's a lot of stuff they "over-built" since they didn't know
any better.

So you are saying they used sufficient margins of safety to account
for the uncertainties in their designs and materials? Egads, what
outrageous deviation from engineering practice!

The problem is defining sufficient. Margins cost. It's a question of how
much the cost is worth it. I suspect that many of the Roman aquaducts will
still be standing long after many modern bridges collapse. Are modern
bridges unsafe or underbuilt? No, they're built the required margins.



Is the stuff that didn't fall down in 2000 years of seismic history
actually "over-built" while the stuff that collapsed "properly built"?

Yes.


Are we saying then that the Pantheon is standing because "they didn't
know any better"?


Partly, yes.

I think your demurrals are straining at gnats.


In central Italy the recurrence rate of magnitude 7+ earthquakes is
700 years of so, so the Pantheon has survived ~3 or so. In
particular there was one in 1349 that severely damaged the
Colosseum. The interior of the building has been remodeled any number of
times,
but the dome has stood without structural maintenance since its
construction in 128 CE.

--
Greg Moore
Ask me about lily, an RPI based CMC.

Derek Lyons wrote:
" wrote:

On Oct 1, 9:49 am, "Greg D. Moore \(Strider\)"

And of course we no longer have examples of all the Roman architecture that
didn't survive because it was poorly built.

It's a self-selecting observation. Like folks in Florida who talk about
homes not destroyed by hurricanes. "They don't build them like they used
to!" Yeah but you're only the seeing the ones that survived, not all the
ones that had previously been wiped out.
True, as far as it goes.

But are you suggesting that the world's largest unreinforced concrete
dome, and the world's largest dome of any kind before 1881, is still
standing because it got lucky? That they could build it at all is an
engineering marvel.

The two statements are unconnected Carey, being an engineering marvel
is no guarantor of being a survivor.

It is often a prerequisite however.

The Colliseum was an engineering
marvel, as was the Parthenon. Neither of them are looking too good
nowadays.

Umm... The Parthenon was doing just fine until it was blown up on 26
September 1687 by an Ottoman ammo dump inside the building exploding.

Greg D. Moore (Strider) wrote:
Carey wrote:
Greg D. Moore (Strider) wrote:
wrote:
On Oct 1, 9:49 am, "Greg D. Moore \(Strider\)"
wrote:
...
But are you suggesting that the world's largest unreinforced
concrete dome, and the world's largest dome of any kind before
1881, is still standing because it got lucky? That they could build
it at all is an engineering marvel.
There's no doubt it's an engineering marvel. But also keep in mind
they were building on previous experience, but successful and not so
successful.
So that's like - everybody, everywhere, at all times, throughout all
of history, right? Is there any time in engineering history when this
generalization isn't true?


It's pretty generally true. Though one could argue that places like Haiti
are the exception.

(I have several books on the role of failure in engineering history
collectively showing its ubiquity, by the way, so this really is just
a rhetorical question.)

And there's a lot of stuff they "over-built" since they didn't know
any better.
So you are saying they used sufficient margins of safety to account
for the uncertainties in their designs and materials? Egads, what
outrageous deviation from engineering practice!

The problem is defining sufficient. Margins cost. It's a question of how
much the cost is worth it. I suspect that many of the Roman aquaducts will
still be standing long after many modern bridges collapse. Are modern
bridges unsafe or underbuilt? No, they're built the required margins.


Is the stuff that didn't fall down in 2000 years of seismic history
actually "over-built" while the stuff that collapsed "properly built"?

Yes.

Are we saying then that the Pantheon is standing because "they didn't
know any better"?


Partly, yes.

Well, you are consistent.

In our culture we don't build anything intending for it stand forever
without requiring continuing maintenance (then when the maintenance
budget is not forthcoming a generation or two hence it collapses, or
must eventually be torn down and replaced). That is a cultural choice.

Cultures that build things expecting them to endure forever (or for an
unlimited, indefinite time), and succeed, are properly building them for
their purposes.

The Roman definitely know how to build roads cheaply that would not last
- that was common practice. The deep foundation roads they did build and
are still usable today was done deliberately and not due to ignorance.