Tornado Ally

[Paul Kranz]

Is anybody ready to build a dome home subdivision in Tornado Alley, yet? I hear dome homes stand up pretty well against tornadoes.

 

Paul sends...

 

[TaffGoch]

I say HOOEY!

I've always been of the opinion that the deciding factors are the
building materials.

A dome, built of 2x4s and plywood, isn't going to fare any better than
a conventional "box" house, built of the same materials.

[Gerry in Quebec]

Do you think the two types of housing, dome and box, would fare
equally well if they were NOT in the direct path of the tornado, but
nevertheless subjected to extreme winds and flying debris? The whole
topic of dome strength in tornadoes was kicked around with some gusto
on the Yahoo DomeTimes discussion group a couple of years ago.

- Gerry in Quebec where a light breeze is blowing

[TaffGoch]

Much was made of the "dome" that survived the last big hurricane in Florida.

That was a Monolithic dome, constructed of concrete (or, at least, surfaced with concrete.) Reportedly, the only damage was from a lightning strike, which took out a small chunk of concrete on an opening edge.

Seeing the earthquake damage in Haiti, where just about everything was concrete (but not ferrous-reinforced,) makes me consider that a dome shape would more-readily withstand earthquake shaking, but I still have a hard time seeing how wind & debris damage could be better withstood with a dome, versus a "box" (building materials being the same.)

I still get a kick out of a quote from Domebook 2, where box houses were suspect, because they slow down the rotation of the planet, due to wind friction. (I hope that was "tongue-in-cheek.")

[Paul Kranz]

In their article on Bucky Fuller in the 1985 edition of Reader's DIgest, "The Man Who Saw the Future," Emily and Per Ola D'Aulaire wrote that a geodesic dome is seven times stronger than any other building in it's weight class.

 

I have heard many stories of how geodesic dome homes have faired much better against man-made and natural disastes than other homes in their weight class in the same disasters. Could this all be a coincidence?

 

Paul sends...

 

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Very high regards,

 

Paul sends...

ReviveTheFlame.com

[TaffGoch]

"...wrote that a geodesic dome is seven times stronger than any other building in it's weight class."

I doubt that they had empirical evidence to support the statement. Stronger, because external forces are more-readily disbursed, due to the radial-array of struts? Likely true, but "seven times stronger"? No one provides the research reference(s) when making such statements (which then get subsequently repeated, as fact, again and again, without question.) Intellectual sloppiness....

[Hector Alfredo Hernández Hdez.]

My domehome is inspirated in RombiCubeOctahedron, two different triangles, 98 makes 1/2 dome. Have a geometry to easy to understood, usefull to people without experience.

 both types of triangles are almost rectangle triangles.

If you want factors chords and draw, just ask to me.

2013/5/23 TaffGoch <taff...@gmail.com>

[Paul From Geo-Dome]

My feeling would be that a dome is more than seven times stronger, but I do agree with Taff that you have to provide some figures to back up an assumption. It shouldn't be hard to at least do some rough calculations to find out.

If we made two structures out of exactly the same materials, say stud with plywood cover, one a dome and the other a typical tract shape building we could compare them, I can do some really rough calcs for wind and snow load so we could find out for sure which is stronger and by how much.

OK to compare we need each building to have the same internal volume and use the same weight of material. I would make the dome a half sphere so a 4v Icosa would work and the tract building twice as long as it is wide with a 45 degree pitched roof. If this sounds fair I'll through some drawings together. Can anyone suggest a suitable volume, I was thinking large shed size rather than house size.

Paul (from geo-dome). P.S are we taking bets! 

On 24 May 2013, at 00:29, TaffGoch <taff...@gmail.com> wrote:

"...wrote that a geodesic dome is seven times stronger than any other building in it's weight class."

I doubt that they had empirical evidence to support the statement. Stronger, because external forces are more-readily disbursed, due to the radial-array of struts? Likely true, but "seven times stronger"? No one provides the research reference(s) when making such statements (which then get subsequently repeated, as fact, again and again, without question.) Intellectual sloppiness....

--

[Paul Kranz]

Paul from Geo-Dome:

 

Since the sphere is the most economical container, wouldn't it be difficult to find a rectilinear building with the same volume and weight class as a geodesic dome?

 

Paul sends...

[Paul Kranz]

Taff:

 

Something they didn't mention was the ease in which wind circumnavigates a geodesic dome. Does it really even matter if the dome is stronger as long as it is more diffucult for wind to move it in the first place?

 

How about a wind tunnel test to see how much wind pressure it takes to move a rectilinear model and a geodesic dome model of the same weight?

 

Paul sends...

On Thu, May 23, 2013 at 7:29 PM, TaffGoch <taff...@gmail.com> wrote:

"...wrote that a geodesic dome is seven times stronger than any other building in it's weight class."

I doubt that they had empirical evidence to support the statement. Stronger, because external forces are more-readily disbursed, due to the radial-array of struts? Likely true, but "seven times stronger"? No one provides the research reference(s) when making such statements (which then get subsequently repeated, as fact, again and again, without question.) Intellectual sloppiness....

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[Blair Wolfram]

Taff,
Are you saying three 2"x4"s nailed together into a triangle and four 2"x4"s nailed into a square make equally strong frames because they are both constructed with the same materials?

Blair

Sent from my iPhone

[Hector Alfredo Hernández Hdez.]

Rather, it is given a Box home, calculate the diameter of the geodesic dome of equal volume corresponding

2013/5/23 Blair Wolfram <thedo...@gmail.com>

[Paul Kranz]

Paul From Geo-Dome:

 

What would you think of using an 8-foot maximum for the strut dimension for a 4v icosa? If memory serves, it would be an approx. 2020 sq. ft. footprint at the half-sphere mark with vertexes on an approx. 50.2-foot equator. It would take 160 triangles. If you used the Pease dome construction system (interior ribbing on 16-in centers, 2 X 4s, 1/2-inch CDX plywood, nails/staples on 3-inch centers, one-inch truss plates at the corners, and recorsinol glue) we are talking about an average of 80 pounds per triangle for a total of 12,800 pounds.

 

Now I don't know how big a conventional building of the same net weight would be, but it most certainly will not have anywhere near the volume of the equal-weight dome.

 

The Other Paul sends...

On Thu, May 23, 2013 at 9:03 PM, Paul From Geo-Dome <ad...@geo-dome.co.uk> wrote:

[TaffGoch]

Heavens no, Blair.  I do indeed recognize the superiority of a triangle FRAME over a square FRAME (since a square can collapse, while a triangle can't.) That's basic physics and engineering.

However, as soon as you attach a rigid skin, stability becomes virtually equal. Then, however, I question how securely panels are attached to frames in contemporary construction. 

I know that Florida changed their building codes, to require security plates, for roofs, foundations, 1st-to-2nd floor, and corner connections, to keep houses from coming apart during hurricanes. I have to surmise that buildings would be even stronger if "glued & screwed" along entire seams, instead of just incrementally spot-nailed.

Some observed strength of many dome homes can be attributed to over-engineering, because building codes don't generally recognize dome construction, and the local approval/inspection folks require a "belt and suspenders" approach, before granting a permit.

_______________

A second issue, regarding roofs, applies to typical roof eaves/overhangs, which trap winds, and contribute to roof tear-off (something domes don't present.) Perhaps, building codes should require hinged eaves? ;)

So, for proper comparison to dome wind robustness, the box house can't have overhanging roof bits.

_______________

Still, my original contention questioned the claims that domes can survive a tornado that a box house can not. Dangerous claims, IMO, potentially instilling confidence where unwarranted.

_______________

This does recall to mind the fact that the Eden Project engineers had to provide heavy foundation tiedowns, because the Bernoulli effect was projected to lift the domes, during high winds, and they needed to beef-up the tie-down features (more so than for typical construction.)

_______________

I do, also, recognize reduced wind resistance. (Otherwise, why do 18-wheelers all now have rounded air dams, to eliminate flat head-on surfaces.)

My most-substantial dubiousness: "...seven times stronger..."

-Taff

[Blair Wolfram]

I'm okay with the overhang change, but that's not how square houses are built. The first effect is there is no way to properly ventilate a box house attic without soffits or eves. Give the square house any (non-real world) advantage available and its still going to lose big time in any engineering comparison.

Blair

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[TaffGoch]

Uhmm, actually, many Cape Cod houses have no eaves or rakes. Perhaps, they were historically-designed to avoid high-wind roof damage (lift-off) from nor'easter storms.

I'm not saying it's a good idea -- just that we've got (to many of) them in central Illinois, too (and I, personally, dislike the look.) I have no idea how the attic is ventilated, which is why I avoided them, when house-hunting.

I agree that a dome is potentially stronger, I just don't agree with over-zealous estimates, or statements that REALLY-high winds can be sustained better (hurricane or tornado.) It's a matter of degree....

[TaffGoch]

I meant to attach....

[Ken G. Brown]

Maybe there's hope for such testing.

http://www.dcnonl.com/article/id51715/--london-ontario-dome-built-to-explore-wind

<http://www.dcnonl.com/article/id51715/--london-ontario-dome-built-to-explore-wind>

<https://www.google.ca/search?q=dome+wind+testing&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:unofficial&client=firefox-nightly>

Ken G. Brown

On 2013-05-23, at 5:29 PM, TaffGoch wrote:

"...wrote that a geodesic dome is seven times stronger than any other building in it's weight class."

I doubt that they had empirical evidence to support the statement. Stronger, because external forces are more-readily disbursed, due to the radial-array of struts? Likely true, but "seven times stronger"? No one provides the research reference(s) when making such statements (which then get subsequently repeated, as fact, again and again, without question.) Intellectual sloppiness....

[Paul Kranz]

Taff:

 

In the April 27, 2003 edition of Parade Magazine, pp. 8 and 10, Marilyn vos Savant wrote in her column "Ask Marilyn," "Round houses do withstand high winds best... Next are square houses, followed by rectangular ones. Worst are L-shaped and U-shaped homes. Roof design is also important. The "hip" roof (pitched on all four sides) withstands high winds best, followed by the gable roof (pitched on two sides). Surprisingly, flat roofs are worst."

 

Do you agree with her?

 

Paul sends...

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[TaffGoch]

Making relative, qualitative comparisons, such as these, the statements do, indeed, appear valid.

When providing quantitative "times" factors (7x stronger,) the revealing research should be referenced. I haven't read such, but would welcome the documented evidence.

-Taff

[Paul Kranz]

On October 14, 1992 (the year of Hurricane Andrew), page 2 of the Baylife Section of the The Tampa Tribune related this story from the San Francisco Chronicle (undated): "Way to go, Bucky! The Dome Information Center has announced  proudly that not a single geodesic dome was leveled by the hurricanes that hit Hawaii, Florida and Louisiana. Buckminster Fuller, inventor of the geodesic dome, would have been pleased, says the center."

 

Paul sends...

 

 

On Fri, May 24, 2013 at 3:39 PM, TaffGoch <taff...@gmail.com> wrote:

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[Blair Wolfram]

TG;

The styles of the architectural roof lines you've pictured date back to times before homes were tight enough to make ventilation matter.

We agree the triangle frame has significant structural advantage and uses 25% less materials than a square. While building a square house, the only way to keep a framed wall from falling over is to brace it, usually with a diagonal 2"x4" brace making a triangle. Once the weight of the roof is on, the triangle brace is removed. The geodesic dome has only triangles, and a dome has larger triangles surrounding these triangles, and these triangles intersect with other larger triangles. If a 4/9 dome has 75 triangle panels, it may have twice that total if you include greater triangles. The most overlooked structural advantage a dome has is tension, overlooked mostly because there is almost none in a square house and most people simply won't think of it. One way to deal with extreme uplift on a square house roof is to add a tension element in the structural design, like cables.

A reasonable comparison between a square house and a dome is to use a 36' diameter 4/9 dome and a square house measuring 25' x 40'. Both have 1000 square feet floor area, and for an efficient use of lumber, mostly plywood, the longest material length on the dome is 8' 0". It may be fair to tweak the square house to 23' or 24' to get better use of 12' beams, but that slightly increases the surface area. It is rare someone ever builds a perfectly square house.

Blair

[TaffGoch]

"...add a tension element..."

That's what Florida building code (now) requires, in the form of tie-together brackets, whether they call them "tension elements," or not. I'd be willing to bet that they won't permit "cables," because they've made the building code too specific.

Office-dwelling bureaucrats in charge! pffft....

[Paul Kranz]

Blair:

 

Would the two structures weight the same?

 

Paul sends...

[Blair Wolfram]

No, not if they have the same floor area. The dome would weigh less.

Sent from my iPhone

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[Paul Kranz]

Blair:

 

Would a better test of strength come from a same-weight or same-volume comparison between a conventional building and a dome?

 

Paul sends...

 

[Hector Alfredo Hernández Hdez.]

weight is'nt matter, good anchors is best solution.

2013/5/26 Paul Kranz <pa...@revivetheflame.com>

Blair:

 

Would a better test of strength come from a same-weight or same-volume comparison between a conventional building and a dome?

 

Paul sends...

 

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[Blair Wolfram]

The use of the buildings are probably most comparable if the square footages are the same, then maybe the volume. The dome will always produce a larger building given the same weight. 

Sent from my iPhone

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