Lemons: Stadium roof

### ODT Online Tue, 9 Mar 2010
Stadium roof ‘will be fine’
The roof on Dunedin’s Forsyth Barr Stadium would be able to withstand a storm similar to that experienced in Melbourne on Saturday, in which hailstones the size of lemons caused major damage.
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Post by Elizabeth Kerr


Filed under Construction, Stadiums

26 responses to “Lemons: Stadium roof

  1. David

    So they’ve tested the roof by dropping cars on it.

    Do you think someone should whisper to them that this is an unlikely scenario?

    And that perhaps they would be better testing for things that are more likely to come from the sky – snow, hail etc.

    And if we had wet snow at depth of the 1939 fall, the roof would need to hold 2000 tonnes (or to put that in terms the stadium may have tested for – that’s around 2000 cars).

    And if the roof would hold 2000 cars without collapsing, then perhaps the lack of parking could have an innovative solution.

    • Elizabeth

      Oh darn, David – you saw straight through Guy Hedderwick’s bizarre claim.

      Any material test data he might supply to support this… would be interesting. Gee, maybe we should ring BRANZ.

  2. I heard second-hand (but from reliable source) that they won’t be able to clean it, as it’s comprised of these very lightweight plastic compartments, which you can’t climb or walk on. So someone has their facts wrong here … maybe me! But the ability to clean it would be crucial one imagines, not least as there is a quarry right over the road.

    • Elizabeth

      Yeah, it’s been described as a “sandwich” ETFE system. It can be easily repaired if holed, although possibly something more required if throwing a Hummer at it from above.
      If the gear hasn’t been stripped out (due to budget crimping), the ETFE roof is supposed to have cleaning gantry(s) as well as water reticulation (plus or minus the theory of self-cleaning – extra to manly assist).

  3. Phil

    Weather is a funny old thing. Commercial buildings have been collapsing on an unprecedented scale through Sweden over the past month as a result of snow loading. And you’d think they would be pretty good at allowing for such things.

    In fairness, however, I think that the stadium roof failing as a result of extreme weather, probably belongs in the same box as tsunamis and rising tides. Yeah, it’s possible, but if such an event should happen in Dunedin, the stadium is probably the last building that people would be worried about.

  4. James

    Any material test data he might supply to support this… would be interesting. Gee, maybe we should ring BRANZ.

    ‘Tis available on the interwebs. I dug it out when looking at issues re:fireworks (really isn’t flammable). Stuff is pretty strong. Stretches by 300% before breaking, and takes 48 MPa to break. Unclear how they do the test, but certainly the one I looked over for flammability was sound.


    • Elizabeth

      I was kidding – we have all the specs but not for a car going through it.

      All in reports and verbatim to Council meetings by Darren Burden; and in evidence given at Stadium Plan Change hearings (Darren Burden; Rex Alexander of Envirocom NZ).

  5. James

    Relatedly, I’d be less worried about the strength of the roof, and more curious about where insurance costs for the stadium are being borne. Just a thought.

  6. The cleaning is something which I feel they may have overlooked. I long ago suggested that the mineral content of the quarry dust from next door, plus the dust from the fertiliser works in the prevailing winds plus liberal doses of seagull guano, will make a good mixture for the growing of lichens. These have excellent adhesive qualities and spread over large areas quite quickly. If this were to happen what then for the light levels for the turf? On any given day one can see literally dozens, if not hundreds of seagulls on the roofs of surrounding buildings. The stadium roof will be a veritable paradise for them.

  7. Phil

    The material is self extinguishing, from memory. Which means it will burn if there is a flame from another source touching it. But will not spread flame on its own. Not that there is a lot to burn in a mostly concrete and steel building.

    It would be interesting to see if there has been anything published on the current condition of the Water Cube structure in Beijing. One would imagine that the pollutants there would create a harsh cleaning environment, and probably as good a test as any.

    • Elizabeth

      Rex Alexander gave evidence (rightly) that ETFE exposed to intense heat vaporises, and will not ‘drip’ or collapse onto people below. Given how ETFE is made, it’s quite a benign synthetic material – the industrial chemical engineers got something right.

  8. Does anyone remember Malcolm Farry and his kicking contest idea? ie Where they’d get players, and others willing, to kick a rugby ball as high as they could to see if there was any possibility of the ball hitting the planned roof height of the stadium and presumably ricocheting off. Well, I presume it was for this reason or did he think if the roof was too low the ball could possibly go right through?! Given they are planning ‘motor sports’ in the stadium maybe they should worry more about the walls than the roof if there is a pile up and an errant car heads into the yonder.

  9. James

    The material is self-extinguishing. Another useful example of its use is in the Eden Project. It’s been there almost a decade AND it has stuff growing inside.

    • Elizabeth

      ETFE has been in use on other projects for 50 years at least… What if? covered most of the aspects last year.

  10. James

    In relation to cleaning, ETFE is one of four compounds sold by DuPont as Teflon (R). So as long as nobody’s up there cleaning it with a steelo, should be fine.

  11. David

    The reply from the stadium spokesman poses more questions than they answer – like

    If it’s “car-proof”, is that only for cars landing on their wheels?

    Or did they test it with cars falling on a sharp corner?

    And what height did they surmise the cars were likely to fall from?

    And what size car do they think will fall – a Falcon or a Toyota Echo?

    Did they test for any other types of falling vehicles? Perhaps trains or trucks (there are roads and rail tracks nearby), or perhaps planes and helicopters – what about boats from the nearby harbour?

  12. Phil

    The Eden Project was referenced some time back. To offer reassurance with regard to the turf growth issue. As was pointed out then, the Eden Project biospheres are open to direct sunlight on all sides. None of those domes have 20m high concrete side walls.

    Someone tried the same tactic by waving the Water Cube complex as an example. We all agreed that the water in the swimming pools inside the cube appeared to still be growing nicely.

    But, in other aspects, one can draw comparisons between the projects.

  13. James

    As was pointed out then, the Eden Project biospheres are open to direct sunlight on all sides
    Most of the domes are built up against the quarry walls, I believe. To be fair, they are open to the south, which is equivalent to the north here.

  14. Whatever may, or may not, happen with the roof or the turf won’t concern the people driving this project. They will be long gone and will leave it to others to fix any problems if they can. Some other city will employ them as consultants, for their expert advice, and so it will go on.

  15. Hiro

    I think the roof will be fine. The only extreme weather in Dunedin is wind and rain. The main trusses will support it to resist winds up to 80km/h.
    I think the roof will be fine and the only stadium to have this material.

  16. ormk

    BMC points out in the ODT online comments today that it would have been expected for preventative measures for seagull roosting to have been made in the initial build. Well yes of course.

    I guess the plan was for a stadium that was both metaphorically and physically covered in shit.

  17. Phil

    Preventative measures were included in the design to discourage seagulls. Problem is that they are all on the outside of the roof, not on the inside.

    • Elizabeth

      As seagulls are to stadiums (inside) so are starlings to packing sheds and shearing sheds… or sparrows to Centre City New World…

  18. ormk

    It seems like such an obvious problem – one that everyone has seen in constructions birds can get into. There are a lot of health hazards associated with bird droppings. I hope they are being cleaned up properly by staff with adequate protection.

  19. Tomo

    Funny how all the birds fly upside down when they fly over the stadium. They reckon it’s not worth shitting on.

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