INDOOR STADIUM PROJECT
My first look at an indoor stadium in 1986 resulted
in a design which was based around the concept of a moving real grass
field ( like the tray in a canary cage) where the whole field, 126 x 78m
for rugby union, is contained in a tray which in turn is mounted on railway
tracks so that it can be moved in and out of the stadium. Such a field
weighs about 5,000 tonne and needs nine rows of track. Ideally the field
should be 4m above the concrete floor below, which allows for the drop
in sightlines when the stadium is converted to court size uses and which
allows the continuing set up and breakdown of a trade fair while the field
is inside. The field can be inside for three days without harming the grass.
If all the lower level seats are mobile (a la
Kingdome) then the field in its outdoor position, where it normally lives
so that the grass can grow, can be used as an outdoor facility for up to
15,000 spectators, leaving behind a 22,000m2 space suitable for trade fairs
and public exhibitions.
Obviously a wide range of events can be catered
for, from trade fairs to concerts to court sports to full field sports
to motor sports, thus maximising the use and the revenues.
Ron Labinski & HOK
When I first worked with Ron Labinski (HOK Sports
of Kansas City, Missouri) in 1986, I began to become more real about the
requirements of an indoor stadium. By 1991 the concept had been refined
and had evolved to the extent that it was readily accepted as viable by
HOK Sports have been the major stadium architects
over the last 15 years. Ron Labinski was once described by Time Magazine
as the world's foremost stadium architect.
Real grass field indoors
With regard to the grass field we ran light deprivation
trials based on what some of N.Z.'s grass experts thought in terms of species,
soil and drainage (we have some of the best grasslands/pasture research
people in the world in N.Z. because of our dependence on agriculture).
Groundsman George Toma at Royals Stadium, Kansas City, also contributed
some valuable insights. We ran the trials at a Ministry of Agriculture
and Fisheries research station under the supervision of Pete Smith, consulting
biologist. We have no doubt that the system as tested will work for Auckland,
and we believe we can design and test successful solutions for other
climates and environments.
An 80m hole in one end
The field requires an opening in the dome 80m wide.
This could be an 80m span bridge which has been designed to carry the reactions
from the dome. However, I've left enough holes in domes and worked with
enough dome fragments to know that a hole can be left in the dome and it
will not compromise the structural integrity of the dome as long as suitable
edge stiffening is provided, along with node hubs which have full moment
capacity around the edge of the opening. The hole just causes a redistribution
of the reaction and axial forces, which can be analysed and allowed for
in the design. (I have also had the experience of two large holes in a
dome, which combined with insufficient moment capacity in the edge node
hubs turned the whole structure into a giant nut cracker mechanism.)
10v OBLATE SUPERELLIPSOIDAL
The dome for a stadium
Later a large dome was designed in 1991 for the
Auckland Superdome project.
It had the following geometry features:
v = 10 frequency
R = basic radius = 115m
Xmax = maximum width = 168m
Ymax = maximum length = 219m
Zmax = maximum height = 52m
above truncation plane
10v oblate super-ellipsoidal icosahedron.
The dome was designed to span from ground
to ground, built first to act as an umbrella for the rest of the project.
It was designed to be built from timber, plywood and LVL.
There is a considerable surface area saving compared
with the "lid on a cake tin" approach.
The reactions are easily dealt with by an in-ground
strip foundation rather than having to deal with these reaction forces
many meters above ground.
During the 1986 study various issues arose, the
most significant being vortex shedding. This and the 1991 study led to
other issues/questions which are discussed below.
+/- 0.5 Cpe in 50m square patches on the leeward
side of the dome is the suggested allowance and combined with the wind
load case governs the design. While not an expert in this area, my gut
reaction is that there are better ways of dealing with this, if in fact
it exists to the extent suggested, other than beefing up the structure.
This could be handled by spoilers and/or aerofoils to minimise the problem
rather than over design the dome.
To what extent can the skin of the dome be used.
Even though the dome is multifaceted, it deviates so little from a smooth
shell that a shell analogy can be assumed (the struts/ribs then are stiffeners
to prevent buckling). The whole structure fits inside the normal criteria
for shell thickness versus span. It may be a matter of dealing with minor
eccentricities. Is a shell analogy a better way of analysing domes of this
Folded Plate Analogy
The dome structure could be considered as a series
of folded plates, with each folded plate being the area inside node-centroid-node-centroid,
and considering the strut and skin as a composite section.
The addition of steel rods or cables could be
considered. These would be attached from node hub to node hub and would
be housed in the V-gap left between 1/2 struts (triangle boundary members).
They would provide the tension capacity required by the governing load
cases, with the balance of the structure dealing with the compression forces.
Could Carbon Fibre/Epoxy be used to help with
tension forces and develop the shell analogy ideas.
In general, the optimised solutions have not
been considered (including optimisation of geometry) and any costings we
have done have always been based on very conservative preliminary design
The world's largest timber dome
at Tacoma, Washington, U.S.A
Cost Effectiveness of a Large Timber Dome
In 1990 we could build a timber dome shell, 10v
superellipsoidal icosahedron, 210x170x55meters high for $18mNZD. Temcor
quoted us $27m NZD for the same in aluminium and Elspan (Hong Kong) quoted
us $24m NZD for a Strarch type of structure in steel.
I believe the large timber geodesic is yet to
take its place - I've confirmed structurally that 1200m diameter is feasible
using existing timber and dome technology.
The economies are all to do with strength
to weight ratio.......
..........and then strength to
weight to cost ratio.
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