Component-based architecture

The Towerdome System is a way of building structures with manufactured components rather than with "raw" materials. Thus, the structure is actually assembled (not built), and can be reconfigured, upgraded or disassembled much easier than currently-used construction methods.


Background and motivation

The Towerdome System is based on synergetics and icosahedral geometry, both of which are not new, used extensively in geodesic domes. To read about this go to our synergetics page.

Geodesic domes, however, only cover space on the ground. We wanted to see if dome geometry can be extended to become truly 3-dimensional and extend up into the air, efficiently supporting weight. Currently, our society is very sprawling over the face of the Earth, severely damaging the biosphere. Somehow, we need to learn how to live lightly on the Earth, minimizing our impact, and allow the biosphere to regenerate. Ultimately, we may create lightweight megastructures that are virtually unlimited in vertical extent and sparse to allow light to filter through.


A new geometric paradigm

The age-old methodology of supporting weight above ground is what we call the table paradigm. Table legs are vertical, which seems very intuitive. Get four legs to hold up a tabletop, and the legs, floor and top form the primal box shape. Its edges have "right" angles and are "orthogonal" (from Sanskrit "artha", meaning "valuable"). The box shape has been ubiquitous in society for thousands of years.

However, what if the table paradigm is not the best methodology? What if right angles and orthogonality have inherent problems? Fuller's synergetics demonstrates that the box structure is not very strong and has a tendency to collapse. Either the joints have to be stiffened where the legs (columns) join the tabletop (platform), or the sides of the box have to be cross-braced (or both). Conclusion: the table paradigm seems natural and intuitive, but can't compete with a triangulated system.


Icosahedral geometry

In a structure system that is sufficiently triangulated, there are no (significant) bending forces at the joints (hubs). Thus the hubs, struts and beams can be optimized for tension and compression only, which makes the system very efficient. With icosahedral geometry, 20 structural members attach to a single hub (see Image 1). Having so many attachments makes the system even more efficient. Of course, the hub must be strong enough to handle what may be very large forces conducted through it. The hub has attachments for 10 horizontal members (beams) and 10 non-horizontal members (struts). There can be 5 struts above the hub and 5 below; thus there is a complete balance between the kinds of members and their directions.

Five-fold symmetry is very unusual in today's buildings around the world. Except for the well-known Pentagon building in Washington, DC, a fairly exhaustive search of the web turned up just one instance of some pentagonal one-story buildings in Maine, and the Texas Commerce Tower in Houston. However, these buildings are pentagonal prisms (i.e. they have vertical walls, etc.); it remains to be seen how people will enjoy a building that is fully icosahedral, with unusual angles. In addition to the pentagonal 108° angles in the horizontal plane, support members angle away from vertical by 31.775° (see Image 1).


Struts, beams, and hubs

In this description, please keep in mind that the components can be scaled smaller or larger depending on how they are intended to be used. As a structural system, it's expected that one or two scales will become standardized. For the towerdome suspension building we chose a scale that produces a height of 8.5 ft (2.6 m) between floors, struts that are 10 ft (3 m) long and a maximum floor span of 16 ft (5 m). A larger scale would give more space between floors, but would also make the struts and floor spans longer, perhaps requiring more high-tech materials and expense.

Floor beam components fit into horizontal docking points in the hub center (see Image 4) and are sandwiched between two half-hubs and fastened. The non-horizontal strut components fit over hexagonal (or circular) docking points on the top or bottom of the hub and are fastened. Again, since the geometric design does not depend on joint stiffness, beams and struts are not required to resist rotation around their attachment points. They only need to resist forces pushing them into the hub (compression) or pulling them away from the hub (tension).

Please note that the strut and beam sizes are "hub center distances"; the physical length of the members is a little shorter (see Image 6) since they attach to the hub at the docking points.


Phi and golden triangles

Image 7 shows how hubs and floor beams form a basic floor area. Horizontally, the towerdome system has decagonal symmetry; the hub has docking points for 10 floor beams. Thus, there are no right angles and the basic shape is a triangle. Furthermore, the three lengths of floor beams are related by the famous phi ratio, 1.618034, also called the "golden ratio", and thus the triangles formed are golden triangles. There are two kinds of golden triangles, "long-short-long" (LSL) and "short-long-short" (SLS) where the ratio of long to short is 1.618.

Golden triangles have a marvelous quality of being subdividable into more golden triangles. In Image 7 the basic LSL triangle shown at the top is subdivided by smaller beams to form three sub-triangles, two of which are smaller LSLs and the third is an SLS. The towerdome suspension building has three differently shaped kinds of floors; however, they can all be completely covered by just these two kinds of floor panels.


Attachment to ground

In order to be complete, the component system needs a method of attaching a structure to its base or foundation. The 3-part structure of the hub assembly provides just such a method; we simply use a half-hub without the usual hub center and bottom half-hub. Thus the large center bolt and ten circumferential bolts that usually hold a full hub together, in this case fasten the half-hub to a flat surface which is the foundation (see Images 8 and 9).

The foundation example in Images 8 and 9 show a very simple structure, a pentagonal pyramid, fastened to a simulated wood floor. For some applications a floor or platform support may be sufficient; however, for large loads a platform is not well-suited and will tend to buckle. Instead, one should use an earth anchor. There are many companies that make these and many are designed for foundational requirements. For example, see LZB, Inc. Earth anchors can function in both compression and tension situations, and can potentially be removed in the event of deconstruction.


Basic wall components

A natural question at this point is, "How do we create walls for a structure?" We have been focusing on efficient structure that can be lightweight and still support significant loads. Walls are technically not part of this consideration, even though standard buildings have, to this day, used walls to provide support and rigidity. According to the Natural Handyman website, "You should consider all outside walls load bearing... When in doubt, assume the wall is load bearing and act accordingly."

By contrast, in the Towerdome Structural System, none of the walls are load bearing. Thus it would be extremely easy to reconfigure a building by upgrading the wall panel components to newer ones, or with interior walls to change rooms according to current needs. When old wall panels are removed, they may be used by someone else or taken to be recycled. Compare this with standard buildings, in which putting in a new wall is either very difficult (because it is load bearing), or in any case a messy, expensive and time-consuming job.

Even though Towerdome wall panels are not load bearing, they may, from time to time, be subjected to loads. For example, vertical walls have to resist the wind, and roofs may get walked on or have snow piled up. The solution, we believe, is to have the wall panels attach to hubs so that any of these loads can be transmitted into the structure in a normal fashion. In Image 10 we see how a triangular wall panel (with its trapezoidal window!) uses floor-beam ends to fit into unused docking points on structural hubs.

In Image 11 we get close-up to our demo pyramid structure (this time built on a pentagonal floor) and look through the windows. The walls may be fitted with weather seals that join with adjacent panels. Of course, no one would want such a small pyramid structure (with no door panel!), but this is offered as a preliminary design.


A glimpse into the future

It should be noted that these designs are not the final designs, but rather the beginning, a place to start. With research, more design and continued development, the components will become much more sophisticated than what is shown here. Initially, struts will probably be made of hollow structural steel (HSS) with steel hubs, and floor beams will be structural aluminum. However, it is exciting to think about the possibilities of using carbon fiber and micro-fiber materials that weigh just a fraction of other materials. The resulting weight reduction in the over-all structure greatly reduces stress on components, allowing them to be more efficient. This process can continue indefinitely.

The "holy grail" of this scenario would be to fabricate carbon micro-fiber or polymer components from atmospheric carbon using solar power and nano-technology to sequester carbon dioxide. Research in this area has been done at the University of Southern California. We could then mass-produce components for all kinds of uses and at the same time reduce atmospheric carbon to combat climate change.

horizontal floor beams (brown)
and non-horizontal struts (blue)


⇑ Image 1 - hub component with all floor beams and struts



zooming in for a
closer look at the hub


⇑ Image 2 - closer view of fully populated hub


⇑ Image 3 - close-up view of fully populated hub



how beams and struts fit into
docking points on the hub


⇑ Image 4 - hub with strut and floor beam attachment



the hub is composed of a
hub center and two half-hubs


⇑ Image 5 - hub separated into sub-components



how big are the components?


⇑ Image 6 - sizes of components



assembling floor areas


⇑ Image 7 - basic floor area



attachment to foundations


⇑ Image 8 - floor-mounted pyramid
⇑ Image 9 - close-up of floor mount



what about walls?


⇑ Image 10 - attaching a wall component
⇑ Image 11 - close-up view through pyramid windows