Previous megastructure efforts
A number of people have considered the issue of how to
construct very large-span enclosed structures.
However, their results seem to me to have been rather
As far as I can tell, few of them have displayed much
understanding of how to construct large enclosed
- Buckminster Fuller
was one of the first to design large domes. His 1,500 meter
diameter [Old Man River City]
clearly illustrates a geodesic dome. The even larger proposed
is also described as a geodesic dome.
Though Fuller invented aspension roofs, his most famous
proposals for creating large spans seemed to primarily
employ compression-based structures that transmitted forces
in their surfaces directly down to the ground - just like an
- Frei Otto once proposed a
[dome covered Antarctic city].
This was to have been an air-supported structure - and from
the pictures, it clearly has no exterior tensile
Since 1971, large air-supported structures have gone
completely out of fashion - with the subsequent discovery
that large tensile structures are practical without the need
for air support.
- After making the first practical cable network domes,
David Geiger pointed out how well his structures scaled
Geiger quickly reported that the diameter of his domes
could be expanded indefinitely with little additional
weight or expense per square foot of roof.
Neither the weight nor the cost increases significantly with increase in span [...]
Geiger was being optimistic here, and his statements must be
regarded as being inaccurate.
His design places large vertical load-bearing masts at
regular intervals across the interval being spanned -
something no self-respecting large-span bridge designer
would do, due to the weight involved needing to be
supported by other members all the way out to the edge
of the structure.
Geiger's design is better than one based on an arch - but it
is no match for the patterns based on large-span bridges
when it comes to covering large areas.
- More recently, a group called
produced a structure which it claims is suitable for
covering large spans.
has a reasonable image of one of their patterns.
Originally, the site claimed:
Larger clear spans are possible than with any other type of structure
They now seem to have toned down their rhetoric a bit -
though the claims made for the structure remain rather
overblown and inaccurate - e.g.:
Xanadomes use less material than any alternative
Their proposed structure is based on an arch, formed into
the pattern of a hexagonal geodesic dome - using a pattern
of radial cables rather like the cells in the ASM dome.
Structures based on arches in compression are fundamentally
inferior at spanning large distances - when compared to
cable stayed structures - and in particular suspended
- Horst Berger writes on the subject of large spans in
his tensile structures book, as follows:
Although arches, respecially in combination with cables, still prove
to remain the most powerful means of covering super-large spans, they also
have a place in short-span structures.
- Horst Berger, in "Light Structures, Structures of Light", p. 150.
IMO, those who deserve credit for pioneering the most
scalable large span technology are probably those
responsible for large cable-stayed structures - such as the
Millennium Dome in London - and the Muna reservoir
cover in Saudi Arabia.
There have been a few other mega-structure proposals - e.g.:
Dante Bini's tower city
Shimizu's proposed tokyo pyramid