Crossposting - Colony Wall Loadings

>
> > I think
> > that the structural design of the habitat will have to be
designed
> > specifically for any extraordinary structures within the the
> > habitat. The ground of the habitat will include dirt, small
hollow
> > hills, lakes, forests, rivers, etc. We can probably estimate the
> > loading that they would place on the structure beneath them. For
> > multistorey buildings, all of that weight will have to be
designed
> > for.
>
> Well, don't forget atmospheric pressure. 15 pounds per square
> inch is 10 tonnes per square meter before you start. Typical
> weight of stone is about 6 tonnes per cubic meter. I'd expect
> that you would want a factor of 2 safety factor on your wall
> strength and then add on other 10 tonnes of building.
>
> So the required strength might work out at 40 tonnes.
>
> Buildings would probably need foundations to even out the load.
>
> > I've even toyed with the idea, within a cylinder habitat, of
having
> > a building near each endcap, that has a ground floor on each of
the
> > three land panels and each of the three buildings rise to join
in
> > the center. The buildings would have variable gravity and join
at a
> > minimal-g recreation center. From there, further construction
could
> > progress along the zero-g axis. But as I've been considering
this
> > plan, I've turned a lot of attention to the load factors that
all of
> > that building mass would place on the ground footprint. My gut
> > feeling is that if these building are designed from the outset,
then
> > the structural design of the habitat could be such as to spread
the
> > load of the building mass.
>
> You've missed a trick. If the building goes to the axis, then
> it should hang DOWN from the axis. Tensile structures are much
> cheaper to build than compressive structures; and it avoids
> putting any load on the rim at all.
>
Cool trick if it works. I know that this is frequently cited in the
work of space tethers, space elevators, but I'm not convinced that
it would work in a habitat. Here's why: the force at work on a
planetary body is gravity caused by the mass of the the planet. On a
habitat, we're dealing with a pseudo-gravity effected through
centrifugal force. I think that would be destabilizing because of
the coriolis effect. Isn't there something to that? There really
wouldn't be a hanging down (implied that gravity is pulling as a
vector towards the surface) rather there would be a combination of
vectors to consider in the engineering.

This leads me to the larger question of how much of
standard "reference book" engineering will have to be rewritten to
substitute centrifugal force for the gravitional constant. Will such
reference tables have to be designed for each new habitat design?

>
> > Just think how cool it would be to go up the elevator in one
> > building, transfer in the zero-g lobby and go down the elevator
in
> > another building. That lobby, having three elevator
orientations,
> > people exiting at different angles. WOW. That would put the
tourist
> > potential of the Empire State Building to shame.
>
> Yes, very cool.
>
> > I fear that it will be impossible to willy-nilly put up muli-
storey
> > buildings in the habitats. Single family homes will probably be
> > tolerable. Office buildings - probably not.
>
> Actually I'm thinking that low gravity is a great place for
> um, sleeping. Other things, and sleeping. Mainly sleeping, but
> other things too. I mean, the other things are tiring. ;-)
> Plus there's the view. So the low gravity would be hotels
> and expensive residences.

Oh yeah, I know, wink wink, nudge nudge, say no more. I think that
such a building would offer opportunity for a wide variety of
experiences, sex, recreation, variable-g living environments,
preparing crews for trips to mars or the moon, recovery suites for
mitigating the prolonged stays on those planets or from zero-g
missions.

But this building (or 3 of them) will be huge. Each will be as tall
as the radius of the cylinder, i.e. 1000m - 3000m. That'll put to
shame any of earth's skyscrapers. But do we need such tall
buildings, coolness factor excluded of course. Think of how much
floor space each would have.

Also, any engineers out there want to venture an opinion on how
construction will change when the gravitational constant is no
longer constant. It will be lessening as the building height
increases. On earth, a steel girder will effectively weight the same
at ground level, 100 meters, or 2000 meters. We can't say the same
for a habitat. How can the engineering be relaxed to compensate for
the wieght of stacked masses not growing linearly but on a
diminiishing curve?
>
> > The habitat as the ultimate planned community. When you reach
plan
> > capacity, build a new habitat. No rezoning allowed. No
increasing
> > densities allowed. It's built the way it's designed.
> >
> > This whole issue of loading has led me to give a long hard look
to
> > concrete construction for the habitats. Concrete can take
impressive
> > compressive loads, but to directly addresss your question - I'm
not
> > sure at the moment how thick the "floor" would have to be.
>
> Habitats have large tensile loads; very few compressive loads.
>
Can you explain a bit more. Please.