The London 2012 Water Polo Venue;
Lightweight temporary design.
Mike Sefton1, Andrew Best2, Matthew Birchall3
1,2,3
Buro Happold, Camden Mill, Lower Bristol Road, Bath, England.
Abstract
The 5,000 seat London Olympic Water Polo Venue is the first Olympic venue
designed solely for the sport. It was also one of the many temporary venues for these
Games and was only operational for the May warm-up event and the Olympics in
summer. Keeping with the themes for these Olympics the venue was designed to
minimise material use and maximize the amount of reusable and recyclable elements
in the construction.
Phthalate-free PVC-coated polyester fabric forms the envelope of the building, using
inflated cushions for the roof and flat membrane panels for the walls. The 10 large
roof cushions span 10m between the 55m wide portal frame structures made from a
kit of modular space frame trusses. The tapering form reduced the overall building
volume, with the maximum 34m height over the main stand reducing to 16m where
a lower roof was possible over the warm-up pool.
Although the building was in use for a short summer period only, the external
structure was constructed during the winter prior to the games. The structure of the
envelope was therefore designed to be strong enough for a full code-based wind
load. However, to minimise the weight of the structure for the venue, operational
serviceability cases were generated using a statistical approach to define lower wind
speeds for average, windy and very windy summer days. These were used to
demonstrate that despite roof cushion and side panel deformations being high under
a full design wind load, during the operational period they would be suitable for the
venue requirements. This analysis meant that significantly longer cushion and panel
spans were viable, minimising the number of trusses needed.
The paper discusses the overall design of the structural envelope with a focus on the
pneumatic and membrane elements, considering materials, environmental
performance and construction and deconstruction.
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Keywords: Pneumatic, temporary, demountable, reusable.
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Introduction
The London 2012 Water Polo Venue is the first dedicated Olympic arena designed
specifically for water polo. It has a 5,000 seat capacity and houses two pools, a
competition pool and a smaller warm-up pool. The bespoke nature of the venue
allowed the design team to optimise the pool size and spectator site lines specifically
for the event, rather than converting a venue previously set up for swimming events.
The venue was in use for two events, a four day test tournament in May of 2012 and
for the Olympic Games in August. Construction started in spring 2011 with the
structural frame and envelope in construction during winter 2011/12.
The whole venue was designed around its temporary nature with the design
facilitating the use of standard supply chain elements and recyclable materials where
possible. This paper discusses these, focussing mainly on the structural frame and
envelope of the venue, and how the frame and envelope was designed to use
rentable equipment where possible and minimise the material quantities by
designing for a short operational period.
Figure 1. Water Polo Venue. Image credit: Buro Happold, Nathan
George
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Venue design philosophy
The temporary nature of the venue was one of the critical factors within the design.
It was aimed to create a building that minimised material use and where possible
used pre-existing elements and/or elements that could subsequently be re-used
afterwards or recycled if not. This led to a ‘Kit of Parts’ design approach where
elements by different suppliers were isolated from each other to enable them to be
constructed and deconstructed independently. These parts are shown in Figure 2.
Figure 2. Elements in the kit of parts. Image credit: David Morley
Architects
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The kit of parts was to be constructed from different suppliers and included the
following elements:
Structural frame and envelope: discussed in the following chapters.
Seating: designed to allow standard temporary seating systems from existing stock
to be supplied and reused after the games. This was structurally independent of the
envelope frame so as to facilitate simpler construction and deconstruction.
Pools and surrounds: Water Polo specific 37m long, 23m wide competition pool and
warm-up pool made using standard temporary pool systems which can be
dismantled and reconfigured for reuse after the games in more standard sizes.
Modular accommodation: using standard accommodation for reuse after the games;
independent from the envelope frame for simplicity of construction and
deconstruction.
Plug-in plant for environmental control: using rentable equipment for the duration of
the operational period.
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Structural frame and envelope
The simplest way to minimise material use for the structural frame and envelope for
the venue would have been to follow the example of some previous Olympic water
polo competitions which have been held outdoors. But the risk of poor weather in
the British summer ruled this out for London! Options for a roof-only venue were
considered initially to provide simple shelter against the rain but it was not possible
to meet the poolside environment requirements for player comfort set down in the
FINA guidelines. Therefore a fully enclosed venue was necessary.
Since the venue was to be in use for a very limited time the material cost, both in
terms of money and environmental impact, would be high in comparison with
energy use. This led to the use of a predominantly un-insulated envelope. However
this created the possibility of condensation forming inside the envelope caused by
the high moisture load from the pool and the warm poolside conditions especially
during the cold evening sessions of the May warm-up event. Condensation on the
walls presented no significant risk to disrupting the operation of the venue, but any
condensation occurring inside the roof would pose a problem and so a certain level
of insulation was required here.
To enable the structure to be made from a kit of parts, a simple frame structure was
designed to be fabricated using supply chain rental stock components. This
comprised a series of portal frames which span across the short axis of the venue. In
order to achieve the relatively large (55m) spans across the width of the venue some
bespoke elements would need fabrication which could then be returned to the rental
market. Figure 3 shows a typical elevation of a portal frame. As can be seen in
figure 4 the height of the portal frames decreases along the length of the building to
minimise the enclosed volume where the height is not required over the warm up
pool.
The structural frame was to be clad with a Phthalate-free PVC-coated polyester
fabric. The use of a membrane as a cladding to span between the frames was an
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economic option and, in keeping with the aims of the venue, is intended for
recycling after use. Inflated cushions were to be used in the roof to provide the
required insulation and minimise the risk of condensation. On the walls where
condensation is less of a problem, single skin panels were used to reduce cost and
material usage.
Figure 3. Short section through venue showing typical portal frame
elevation and cut through long span of roof cushions.
Figure 4. Long section through venue showing cut through short
span of roof cushions.
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Optimising enclosure design for temporary use
Minimising material use was a key principle for the venue and therefore design was
carried out to achieve the maximum the roof cushions and wall panel span in order
to reduce the number of portal frame trusses required.
Although the venue is only temporary, construction was started over a year before
the Olympic Games, with it also being unclear when the venue would be
deconstructed afterwards. Since the construction of the envelope was to take place
during the winter and it would be in place for nearly a year it would certainly be
exposed to the worst weather conditions in the British calendar. Therefore it was
necessary to design the structure in the ultimate limit state to be strong enough to be
safe for a full design code wind speed.
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However with this being a lightweight fabric structure the movements of the
building under the full code wind speed would be considerable and if the venue was
in use in these conditions could cause discomfort to the occupants. This would be
the case mostly in the upper rows of seating where the crowd are close to the roof
cushions and deflections would be very noticeable. If this was to be a permanent
year-round venue the serviceability criteria would probably be the limiting design
factor to how far the roof cushions and fabric could span.
However, since the venue would not be occupied when the highest wind speeds
would occur, it was essential to account for this in the design. Therefore, reduced
summer wind speeds were calculated to check likely operational fabric deflections
and enable spans to be limited by the strength capacity of the fabric.
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Establishing winds under temporary periods
A statistical approach was taken to establish site wind speeds which would occur
during the May to August period. Local MET office data was used with long term
wind statistics to calculate these. Three levels of wind speed were calculated with
different possibilities of exceedence during the summer operational period:

Average summer day - 50% chance of exceedence.

Windy summer day - 5% chance of exceedence.

Very windy summer day - 1% chance of exceedence.
The values for these wind speeds are shown in table 1 where it can be seen that the
likely wind speeds and associated pressures during use are significantly lower than
for the full design wind speed.
Condition
Wind
Speed
Peak (gust)
velocity pressure
qp(z)
m/s
kN/m2
Full code-based design wind speed
39.2
0.96
Stress &
Deflection
Very windy summer day (1%)
17.5
0.19
Deflection
Windy summer day (5%)
14.9
0.14
Deflection
Average summer day (50%)
6.7
0.03
Deflection
Table 1.
Calculations
Carried Out
Wind speeds used for design.
It should be stressed that the summer wind speeds calculated would not be suitable
for and were not used for any element strength checks and that the deflections
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occurring during the full design wind speed were considered to ensure that no
damage could be sustained by the membrane in these conditions through striking
any adjacent structure or otherwise.
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Results of using reduced summer wind speeds
There is little guidance for deflection limit criteria for fabric structures. Provided
that clash checks are made, that dynamic response is not problematic, and that the
details are designed to allow for suitable angle changes at supports etc, designers can
be confident that damage will not occur under serviceability cases. Given the large
magnitude of deflections that can occur it is often the perception of occupants that
becomes the critical limit and this is a very difficult limit to judge. As such, for the
Water Polo Venue at an early stage in the design deflections were assessed under the
three different summer wind speeds to give a feel for how different the deflections
might be on different days. This was intended to build a picture of the behaviour of
the membranes and to give confidence that the deflections would not feel too high in
use and enable the design to progress with confidence.
Typical non-linear analysis of the roof cushions and side panels was carried out to
establish the feasibility of the large spans. A 10m span was calculated to be around
the maximum achievable for fabric stress limits given the ultimate limit state applied
loads and therefore deflections under the different load levels were checked for this
span.
A 10m wide and 52m long cushion with a slight arc to follow the curved lines of the
portal frames was analysed using a constant mass assumption. The cushion had a
rise of approximately 1.1m in both the upper and lower surface with an inflation
pressure of 0.4kN/m2.
Under the full design code wind speed, analysis showed that the external membrane
deflection would be as high as 340mm with the internal membrane showing signs of
rippling and slack. In the upper rows of the stands - where people are close to the
cushions - this behaviour would have been very noticeable and likely to be quite
disturbing for spectators in the closed environment. This would have been
unacceptable if it occurred during an operational period. An analysis image showing
the possible shape under full code uplift loading is shown in figure 5 and can be
compared with figure 6.
Figure 5. Deflected cushion with code wind speed applying an uplift
pressure – note ripples on underside.
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The analysis of the summer wind cases, however, showed that even on a very windy
summer day (1% chance of exceedence) deflection of the internal skin would be
limited to around 40mm which would definitely be acceptable for such a membrane.
Importantly there were also no signs of rippling or slackness in the surface. Table 2
summarises the cushion deflection results and shows the benefit of using the reduced
wind speeds to assess the deflections during the operational period.
Figure 6. Deflected cushion on very windy summer day – deflection
not noticable.
Deflections of the flat wall panels (figure 7) were much higher than the cushions
since there is no initial curvature of form. Using reduced summer wind speeds,
deflections are much more acceptable although they are still relatively high.
However spectators would not be as near to the panels to observe the deflections
closely since there is a hard façade at lower levels and an internal fabric screen to
the inside face of the portal frame columns covering the external skin (these can be
seen in figure 8). Table 3 summarises the wall panel deflection results.
Figure 7. Silver flat fabric wall panels with blue hard façade at low
levels. Image credit: Mike Sefton, Buro Happold
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Wind speed condition
External surface
deflection
Internal surface
deflection
mm
mm
Full code-based design wind speed
343
Signs of rippling and
slack
Very windy summer day (1%)
101
+41 / -11
Windy summer day (5%)
80
+30 / -8
Average summer day (50%)
21
+11 / -2
(Uplift load case)
Table 2.
Cushion deflections under different wind conditions.
Wind speed condition
(Uplift load case)
Flat wall panel
deflection
mm
Full code based design wind speed
960
Very windy summer day (1%)
510
Windy summer day (5%)
440
Average summer day (50%)
200
Table 3.
Wall panel deflections under different wind conditions.
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Figure 8. Water Polo Venue in action at the test event in May 2012.
Image credit: Buro Happold, Mike Sefton
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Conclusions
Statistical analysis was used to assess likely wind speeds for the operational period
of the temporary venue for the London Olympic water polo competition for
comparison with the full design wind speed. The resulting wind pressures were used
to calculate deflections of the relatively large PVC-coated polyester fabric roof
cushions. This showed that although peak deflections occurring during the winter
period would be unsuitable for the venue to be in use those that would occur during
operational periods would be satisfactory. This enabled the cushion spans to be
increased to the limits imposed by the fabric strength and minimising the number of
portal frames.
References
[1] BS 6399-2:1997, Loading for buildings – Part 2: Code of practice for
wind loads.
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