Concrete Geodesic Dome

[TaffGoch]

Hi, all,

Has anyone seen any information on this dome?

I found the image on a pinterest website, with no associated description.

It was a Russian webpage, so that's all I can guess at.

-Taff

(aka, TaffGoch, David Price)

[Gravity]

I believe I remember this guy posting about this dome, himself, in this very group.

Adam Winter

The Bootstrap Music Co.

206-430-4425

bootstrapmusic.com

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[Dick Fischbeck]

I think the spherical block man, Peter Roberts in upstate NY, Alfred Station,  works this way.

https://www.masonrymagazine.com/blog/2020/07/21/spherical-block-llc-a-new-way-to-build-with-masonry/

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[valle....@gmail.com]

hi. I'm looking to find more info too. only found the webpage but don't have info only the pic.

here ....    http://ivgazeta.ru/read/14988 

[RC]

I think those are molded aerated concrete. They are lightweight and insulating.  Also, window openings can be cut out using a hand saw.

[Pedro valle]

Hi

following this tutorial [Make Abstract Models with Geometry Nodes - YouTube] (https://www.youtube.com/watch?v=K5eNdCpoRD4&t=346s)
manage to build an ok dome. in Blender. made the dome, then export to OBJ and open in Pepakura and unfold the dome, but I can't make the hexagons small like the pic above, so my molds are maybe doble the size, the dome is 10 mts on diameter. I'm planning to build this dome with aircrate in summer Ill post my progress on June. thanks   to these group for all the help. 

On Tuesday, June 7, 2022 at 3:51:51 PM UTC-7 TaffGoch wrote:

[RC]

Your hexagon sizes are bigger because it is not the same model as the picture. Compare with the marked up picture.

[Ashok Mathur]

From a theory point of view Concrete Geodesic Domes:

Concrete has near-zero tensional strength.

It can not be used to make tensgrity structures.

Here the term concrete is being used as a shorthand for Reinforced Cement and Concrete Structures.

RCC structures have good tensional strength and can be used to make tensegrity structures.

Secondly, tensegrity requires islands of compression elements surrounded by continuous tensional structures.

By casting RCC in hexagonal blocks, tensional elements no longer surround the compressional  elements.

You end up making a compressional dome which stays together by interlocking and inertia.

Regards

Ashok

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[lemondealc]

Is there any cast shape that would have both the islands of compression and the tension? 

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[Pedro valle]

Hi  Robert .. 

I changed the subdivisions from 3 to 4 and  I thing I get   the same dome as the pics. the only thing Blender don't make all the hexagons the same size, they are not symmetrical. is another software like maybe solidworks that will generate a dome with hexagons symmetrical? or all the 3D software make these dome the same way? I'm traying to make only 3 molds 

 

[Pedro valle]

Hi Ashok

thank you for your reply .so building a dome with aircrate is no safe? will be better wood or metal?  appreciate you advise.   

[Ashok Mathur]

Dear Pedro

I am not saying that a aircrete concrete structure is unsafe.

I was merely trying to distinguish between the mathematics 

and physics of a structure.

Deriving coordinates of vertices from a geodesic dome alone 

does not make the subsequent structure geodesic in nature. 

You have used only the mathematics of the geodesic dome 

but cut out the physics by casting the structure in separate 

disjointed blocks.

You can make an aircrete geodesic dome by casting the panels

of aircrete but joining the retaining structures till they form a continuous 

tension ring around the aircrete.

By the way, I spent the third week of October in Istanbul

surrounded by about 100 compressive spherical dome that soar

over 100 feet in the sky. Properly made spherical compressive domes

are also long lasting structures.

Some such domes at Istanbul are about two milineum  

old while others are several hundred centuries old.They transfer their 

weight from the circular shape to a square foundation using a unique in

 between called squinch.

Persian domes transfer their weight to an octagonal base using another in between.

Compressive spherical domes of aircrete are also possible 

but will use a maths different from geodesic.

Regards

Ashok

Sent from my iPhone

On 17-Nov-2022, at 7:53 AM, Pedro valle <escap...@gmail.com> wrote:



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[Pedro valle]

Hi Ashok

                     still working on the design, I'm using Blender 3D   but the shapes are no symmetrical so if I made the molds, I'll need to make a lot because no all the hexagons are the same, I will try different method in blender I just saw another way to make a dome, I would like to travel and see all those places like Istanbul and Rome to see the Pantheon.

last summer June and July, I made a roof with almost 2,000 bricks, using a wood mold to hold the bricks till they dry then I put a wire mesh and then plaster. I made 3  Bóvedas, in Spain I think they call them  Bóvedas  catalanas o Bóveda de cañón, don't know how they call them in English.

and I will have off June and July again. so, I will try to build a dome, with concrete because is way cheaper that metal or wood.    

[Dx G]

Interesting discussion. Please keep in mind that some parts of a dome can actually be in tension, rather compression, depending on the design.  Many of the older domes have a tension band/ring/belt, buttresses or some mass at key points near the base to prevent any bulging.  Often they are not visible.

DxG

[RC]

Pedro,

Near the equator of a spherical dome, the compression forces transition to tensional hoop stresses.  Perhaps you could build a light-weight metal tube geodesic dome as a supporting structure first.  Then, assemble hexagon blocks like the one shown below onto each hub.  These have grooves molded into them that straddle the metal conduit.  The hex blocks could be sized so that their is a small mortar gap between blocks.  The gaps between blocks would take care of tolerance build up errors, and would be filled with mortar.  The concrete blocks will be great for enclosing the structure and handling compression forces.  And, the metal conduit dome frame will resist tensional forces.  (had to repost again because I drew the block incorrectly)

[Pedro valle]

Hi, Robert C. 

that's a great idea, in the pandemic, my employer sends me home for 3 months, so I bought a welder machine and learn the basics of welding no like a pro, but I can build the metal structure. and on top I can put the metal mesh and plaster. my plan is built cylindrical shape 8 feet tall with a door maybe some windows and in top the dome. fells like that way dont waste space and making a door in the dome is kind hard. 

[RC]

Sounds like you made good use of your three months off!  The grooves of the blocks would face inward.  I was imagining a support dome framework made of flattened end tubes bolted together.  The grooves would be fairly deep so that you could mortar over the embedded tubes.

[Pedro valle]

oh. even better because will be faster to build. I saw some videos how to build domes that way. mean just the flattened end tubes technique, no with concrete.  just need to find the design.   thank you. 

[Pedro valle]

found how to make domes with the flattened end tubes 

4V Geodesic Dome Calculator Software in Feet and Inches for Calculating Strut Lengths - Geodesic Dome Plans (ziptiedomes.com)

4V 5/12 Kruschke geodesic dome calculator » Domerama

Make a Geodesic Dome From Steel Tubing : 13 Steps (with Pictures) - Instructables 

I need to find metal pipes, the cheapest, I found was $11    1/2''x10' steel. but the cooper ones are $13  

[Erich Nolan Bertussi]

this was a great thread to read guys.

i wonder in your scenarios are you utilising the single exact same irregular hex and single exact same irregular pent shape for the dome?

I hope to be doing something like this and pre-fabing passivhaus compliant hexes and pents...

so this thread is awesome for me!

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[Patrick McDonnell]

Hi,

I am interested in making this style of dome using concrete molds. Obviously trying to keep the number of different molds to a minimum.

I have tried a number of times to model the geometry in CAD from first principals but I usually end up with the outside being ok but the panels not lining up properly on the inside.

I would like to be able to model this in CAD with 'prefect' geometry from first principals, is this possible? I have done extensive googling and searching through this forum and the closest thing I have found is mention of Goldberg division but could not find enough information to make this work.

Any pointers would be much appreciated.

Cheers,

Paddy

[Levente Likhanecz]

Chris Kitrick has this hexagonal dome. Its obviously looks higher frequency. All hexa is flat, and all vertices on sphere

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[Dx G]

Patick,
  You said

"Obviously trying to keep the number of different molds to a minimum."

Bingo.  

An important part of choosing the right design of a dome (or almost anything, for that matter) is keeping the variation in parts and part size to a minimum.  This reduces cost, increases simplicity and makes success more likely.

 Firstly, with respect to concrete block domes, if you look, you will specifically see that this was partly addressed in Robert's patent.

https://patents.google.com/patent/US10487494B1/en

 He discusses using mortar to fill the space between blocks when they are used for a larger or smaller dome, as this changes the dihedral angles. There are other ways to do that, but its a start.

However, there are also some options in design that are very frequently (and sadly) overlooked.  Some have been discussed in this forum under various topics.  I've been looking at these myself for the creased diamond panel domes I've been evaluating.  So let me mention a few here.

1) Pentakis Dodecahedron
This is similar to a 2 frequency Class 2 Method 3 (triacon). The nice part is like the triacon, although all the panels are the same,  in the Pent Dod, all the dihedral angles are the same. There are some limits on dome size, but the edge-up configuration provides a nice truncation.  Gerry posted some really good material on this.

2) Edge up 3f
A dome that has been popular for decades is the 3f ico alternate. However, one approach few people seem to consider is the edge-up configuration, which provides a flat truncation for a hemisphere.  People often bring up the Kruske dome, which has its assets, but low variation in parts is not one of them.

3) Catalan solids
This is an entire class of polyhedrons with this description:

"Catalan solids are a group of thirteen convex polyhedra that are the duals of the Archimedean solids. They are characterized by having faces that are all the same type, constant dihedral angles, and specific symmetry properties, but their vertices are not symmetric."

 Excellent resource.  There are lots of them if you look.
https://dmccooey.com/polyhedra/
https://dmccooey.com/polyhedra/Catalan.html

https://www.qfbox.info/4d/catalan3d

https://mathworld.wolfram.com/CatalanSolid.html

There is more out there, but this is a good start for you and others that understand the value of reducing variation in the structure.

Remember, every success begins with the decision to try.
 John F. Kennedy

Let us know if this helps and what else might.

Dx G