Geodesic Dome Research Part 1

A geodesic dome is a spherical or partial-spherical shell structure or lattice shell based on a network of great circles (geodesics) on the surface of a sphere. The geodesics intersect to form triangular elements that have local triangular rigidity and also distribute the stress across the structure. When completed to form a complete sphere, it is a geodesic sphere. A dome is enclosed, unlike open geodesic structures such as playground climbers.

Typically a geodesic dome design begins with iconsahedron inscribed in a hypothetical sphere, tiling each triangular face with smaller triangles, then projecting the vertices of each tile to the sphere. The endpoints of the links of the completed sphere are the projected endpoints on the sphere's surface. If this is done exactly, sub-triangle edge lengths take on many different values, requiring links of many sizes. To minimize this, simplifications are made. The result is a compromise of triangles with their vertices lying approximately on the sphere. The edges of the triangles form approximate geodesic paths over the surface of the dome.Geodesic designs can be used to form any curved, enclosed space. Standard designs tend to be used because unusual configurations may require complex, expensive custom design of each strut, vertex and panel.

Construction of geodesic dome

Fuller’s geodesic dome is a grid of triangles, connected in the form of a sphere (hemisphere). The basis for such triangles may be metal rods, plastic tubes, wooden beams and other materials. The cells of the grid are glazed (without losing in functionality you can turn more than 50% of cells into windows), insulated, and covered by finishing materials.

Usually the details for geodesic dome are produced by manufacturing companies. The consumer receives a ready-to-go “construction set” with an illustrative manual on how to assemble it. You will not need any building cranes or other large construction equipment to assemble small and medium sized dome homes.

To assemble a properly designed geodesic dome is very easy. The proof of that is one of the first such domes, which was designed by Fuller as the US exhibition pavilion for the International Trade Fair. The structure with a diameter of 30 meters, made ​​of aluminium tubes, was put together by several unskilled Afghan workers, who didn’t even speak English. They didn’t even need the instructions, because they easily assembled the dome guided only by the coloured marks on the details.

 Types of geodesic domes

Basically, in their structure and design these domes do not differ from each other. The only difference is in the degree of triangulation. Or, to put it more simply, in the number of triangles and their sizes.

So, if there are fewer triangles and they are quite large, then the house is built faster, and less material is used. But if the sides of a triangle are too big, you can have an issue with building materials, because their length is generally limited to 2.2-3 meters.

The shortcoming of a dome with a small number of triangles is its angularity.

A dome with a large number of triangles requires more materials for the ribs of its structure. But it is smoother, looks more like a sphere, is more streamlined and has seismic resistance.

Advantages of geodesic domes

• Durability and lightness (relative) of a geodesic dome increases with its diameter.

• Geodesic dome does not require expensive and highly durable foundation.

• Without detriment to the construction you can glass over 50% of the surface of the dome.

• Such dome can be assembled by a person with a minimum of training.

• For smaller domes you don’t need heavy construction equipment.

 Disadvantages of geodesic domes

Even with a large number of triangles, the shape of the dome is a bit angular.

There is a risk of working with careless manufacturer (there are a lot of those) and to get a house that is not solid enough because of the low quality of its connection nodes.

It is difficult to independently produce the ribs and connectors – because of the difficulty of calculations.

Non-standard windows and doors, which would be more expensive than regular ones.

Another shortcoming of geodesic domes is that their triangular shape is not well suited for the use of finishing materials. But we all know that a bisected rectangle (and this is the shape that majority of building materials are sold in) turns into two triangles. So if you approach your construction with creativity, you can minimize the loss of materials.

By: kailun Liang
      Huynh Van Thao