Designing a Hyperbolic Bamboo Dome in Vietnam

Hi! I am Eddie, a 74 year old retired civil engineer. I am from Scotland in the UK, though I am presently living in Hanoi, Vietnam. As a civil engineer, I have been involved with structures all my working life – albeit structures of a completely different nature. 

In living in Vietnam, I have come across several bamboo structures which have intrigued me from a structural perspective. However, I was also intrigued why there aren’t MORE bamboo structures in a region where the material is in abundant supply. And so from that my interest developed. This took me online and I started to dig and delve on the web into all matters bamboo. Through that research, I came across the BambooU course. I enrolled in it as I was confident that such a course would be worthwhile to help develop my bamboo knowledge.

Prior to the course, my knowledge on bamboo was very superficial. The course immediately gave me a much greater depth of knowledge and understanding on all matters bamboo. I learned about the many different types of bamboo, propagation, harvesting, treatment and conditioning, and preparation for use in construction. All of these I now see as essential knowledge if I ever want to take on a project on bamboo construction. 

But the main thing I got out of the course was inspiration. With the enhanced knowledge I now had from the course content, along with what I gained from the course instructors, from the seminars with expert practitioners, and from my course colleagues, the course didn’t just widen my knowledge, it gave me great inspiration that is now propelling me forward on my bamboo journey!

The project that I created for the course came wholly out of what I learned on the course. In this case, hyperbolic paraboloids caught my interest and from that I made several model panels. From that I realized that each panel constituted half an arch structure. Thus, I realized that if I combined this with several other ‘half arches’ in a circular fashion, I would have created a self-supporting dome structure. So my project just led into itself rather from starting with a pre-conceived idea in mind.

Related: Designing a Bamboo Pavilion During an Online Course

The idea for the structure came from inspection of a basic hyperbolic panel. When viewed from the side, it presents a shallow arch shape. However if this shallow arch is tilted at a 45° angle, it represents half of a full arch. When put head to head with another, these half-arches create a full arch structure.

These half-arches when joined at the head point provide stability to one another length-wise, but they have no lateral stability. However, if several of them are arranged in a circle with the panels being contiguous with one another, and they all meet at a zenith top point. This way, the stability is achieved all round. This results in a dome-type structure.

One main challenge was that the hypar panels create the arch shape when opposing vertices are ‘pinched’ together… But they flatten out again when released.  I wanted the arch shape to remain, so I managed that by tying the ‘pinched’ vertices together (in the short-term). While the arch shape was held I stiffened the panel edges with “edge beams”. I cemented these beams to one another at the vertices and further stiffened each one with fish (i.e. stiffening) plates. When this was completed, the ties holding the vertices could be removed and the panels held their (now) arched shape.

I had no real idea how many half-arches would be required to complete the circle – I was just working directly with the model hypar panels. I was not working off any drawings nor had access to any 3-D visualization software at the time, but it turned out that 7 panels fitted almost perfectly into a full circle.

The resulting dome structure was very pleasing architecturally in that each panel gave the roof a ‘scalloped’ profile.  However, the resulting geometry of the dome was such that the point where the vertices of adjacent panels meet was too close to the dome center. This severely reduced the usable floor space.  I worked around this by adding in “canopy covers” (coming off the main hypar panels) and thus allowing full use of the available floor space.

The final dome has no internal columns or supports and leaves the floor-space completely unimpeded. This allows the dome to be viable for many activities where people gather. Finally for the roofing details, l I tried to imitate a natural thatch (alang-alang grass) but other materials could be used if it were built.

To move further with the design, the use of natural light could be incorporated by adding a cupola to the center. Depending on the size and species of bamboo poles used, I feel the structure should be quite robust. Additionally, the use of only 7 foundations should simplify the sub-structure requirements. While I do believe that the construction of a full-scale structure is very feasible, I currently do not have plans to build it.

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