Ground support collapse Jerusalem
Posted 18 April 2012 - 09:42 PM
Reminiscent of Indianapolis:
An initial investigation revealed that a cable connecting the lighting fixtures was torn apart and as a result, the fixtures collapsed and dragged a concrete cube that weighs a few tons.
Anybody with better sources of information?
Posted 18 April 2012 - 10:05 PM
AV technician & sound engineer
Auckland, New Zealand
"Technician like ninja... live in shadow... move in silence"
Posted 19 April 2012 - 01:29 AM
The outdoor "roof" industry isn't that old, so in terms of have incidents such as these always happened, certainly not in the same way. I'd guess that there could have been deaths from failed scaffolding structures etc.
In terms of 'is this happening more frequently' - that would be an interesting statistical analysis - but it certainly seems to be.
There is a lot to be discussed on this subject - especially as we now have some very detailed analysis of the types of real world stresses and failure modes occuring in outdoor temporary structures, thanks to the Indiana report. One can't but help feel that there will be some sort of tightening of regulation and inspection...
Posted 19 April 2012 - 07:13 AM
Ground support was primarily heavy steel structures engineered within an inch of their lives.
In the last few years we have seen the emerging of cheap alloy structures often operated by companies as an 'add on' service and undercutting specialist companies.
It is those structures that seem to cause most of the problems.
Often the lack of expertise lead to not understanding the forces applied to these structures and calculations, if any, based on very optimistic data.
I believe that to be the main cause of the recent collapses.
I don't have enough information on this incident to comment, but looking at some of the newspaper pictures, the span looks quite scary despite the size of the truss.
I hope some of the Israeli members may be able to provide some more detail.
Posted 19 April 2012 - 07:29 AM
Posted 19 April 2012 - 08:04 AM
As far as the reporting goes even in Hebrew it is terrible because the people reporting about it have no idea what they are talking about, when I first started hearing about it it sometimes sounded like just 1-2 fixtures came crashing down or maybe a bar or something like that, obviously the whole structure got blown over.
As far as the companies involved, the lighting company is (I think, from my experience with different companies in Israel) one of the most professional companies here with an overall experienced crew, the company that built the rig has also been doing it for at least the past 4 years.
They've always had strong winds but yesterday there were exceptionally strong winds, obviously that is no excuse and proper measures should have been taken (like lowering the rig if I understood the Indiana State Fair collapse event reviews properly).
According to an article on the Jerusalem Post the structures have to be able to withstand 30 knots of wind and wind gusts yesterday reached 37 knots.
The rigging company today claimed to Ynet that they had been called some time before this happened and that one of their crews was on the way to try and secure the structure and that the security officer should have evacuated at the time he called them instead of continuing rehearsal, if this is true that is a terrible mistake which I guess a "the show must go on" attitude helped create...
The structure itself I think is mainly aluminium trussing, but I can't sure since I am not with the rigging company I have never had to lift their pieces.
The event itself is probably one of the highest budget/largest events that happens in Israel every year, and generally better engineered then anything else (which I guess is not a very good thing for other events)
This post has been edited by Keeper of the Keys: 19 April 2012 - 08:04 AM
Posted 19 April 2012 - 09:59 AM
Thank you Keeper, 40 MPH is not a huge wind speed though the rig should have been lowered and they obviously had no proper Showstop procedure in place. The fact that the rigging company "assumed" the security officer would call it shows there was no specific procedure otherwise I would have "assumed" they would have instructed evacuation. Keep us posted, please.
In the new HSE website Here there is not only a section on TDS but the first mention by HSE of Showstop procedures, as far as I can remember.
Roderick already knows this but the US staging and production industry has a new Event Safety Alliance that is holding meetings with officials in Indiana next week, they have confirmed that they will be using the UK IStructE guidance on TDS in whatever guidance they eventually publish.
Simon and Roderick remind everyone that in my day building stages the structural elements were steel and aluminium trussing, after its' invention, was used for sub-structures if at all. The point here being that we used to have structural drawings and skilled scaffolders involved in every construction.
In a thread on TDS I suggested that we might well see some form of CDM regs introduced. The introduction next October of FFI by the HSE seems to make this more likely than ever. That is a guess. It is also a guess but as there is little difference between an arena rock show and a major opera set I think large-scale theatre may need to urgently rethink its approach. That includes the education of technical staff.
Whether or not the frequency of disasters is rising, the UK industry is ahead of the game with the IStructE guide which was a response to the Birmingham screen collapse (in part) but my personal feeling is that structures designed with arena and stadium shows in mind might be being used out of context. They also appear to be being supervised by people with insufficient knowledge and experience.
This quote from an Israeli news source sounds insane.
They have detained three people for questioning and the mother of the young woman that died s assistant to the manager of the venue, which makes it even worse.
Posted 19 April 2012 - 05:21 PM
- The production staff had just noticed the potential problem and called for the security adviser to tell them what to do, in addition they asked people from the rigging company to come out and look.
- The security adviser had just started inspecting when the whole structure collapsed.
The police currently suspect that there was too much weight hanging from the rig, and when the wind got too strong that resulted in one of the anchor cables snapping after which the structure collapsed.
Whether the ceremony will or will not happen is still up in the air.
//Edit: They are really playing the blame game big time... each article with a different point of view has a different story.
This post has been edited by Keeper of the Keys: 19 April 2012 - 05:45 PM
Posted 23 April 2012 - 01:41 AM
Wind speeds are quite often exceeded, look no further than Tornado Alley in the USA, but when there's promoters involved, and people who have vast amounts of money at stake, then the'll always be a compromise.
www.livesoundandlight.co.uk or www.bryantacoustix.com
Posted 30 April 2012 - 10:55 PM
I put some pictures here:
I heard several different versions about what happened.
A friend of mine who's a volunteer firefighter and was summoned to the location seemed to think that one of the anchor wires had contained some welded bits instead of being just anchor cable with a ratchet mechanism, this to shorten a too long cable. To be honest this version sounds very unlikely to me, and maybe this guy didn't understand, or I didn't understand him.
The lighting crew that was there to do the setup thinks that one of the anchor weights was put on a surface that it shouldn't have been on:
It was on a raised garden bit with the walls around that garden instead of on the ground. Apparently the head of the crew that built the rig had decided that that location was better then the ground just in front of it because the angle of the anchor line would be closer to (or exactly) 45 degrees.
The weight then got pulled of the wall and though it fell 20-30cm that did not compensate for the fact that the anchor location had moved a lot closer and so the anchor line was slack leaving an unanchored structure on the plaza, after which the structure came down within a short period of time.
As a replacement to big trusses were brought in and suspended from construction cranes, with anchor lines to prevent them from swaying too much.
Posted 01 May 2012 - 12:33 AM
To my inexpert eyes, that looks like an awfully small anchor for such a large structure. Roughly one cubic metre of concrete maybe?
One of the findings of the report into the Indianna State Fair collapse was that the "Jersey Barriers" being used as anchor points weren't up to the task. They didn't provide enough weight and slipped easily once the structure came under strain. Permanent fixing points would have been far better, and reasonably practicable since the fair is an annual event and the structure had been used in the same location for many years.
This situation seems very similar - it will be interesting to see what conclusions any investigation reaches.
Posted 01 May 2012 - 08:05 AM
I forgot to say, those pictures were taken by Benjamin Jinj (of Kilim).
Posted 01 May 2012 - 10:05 AM
If the ground is a sort of mix of dirt and stones (from photo) then the friction may not be that great after all. Plus the guy ropes must be at an angle to the weight of the block so to speak and possibly a gust of wind could lift the block and decrease the friction to much less than the weight bearing on the ground.
We read of another instance with the Jersey barriers (I think that is the term) in the US where similar occurred and they moved in gusts. It may be that the science was not that clever after all when taking into consideration the gusting effect.
Our "tent" is smaller than those stages but the ground anchors consist of nine two metre cubes of concrete buried in the ground. These provide the anchors for the ends of the principal rafters. In the least case to a depth of a half metre into the ground and in the "best case" buried almost completely. The lateral movement in any direction is resisted by hundred of tonnes of earth.
The engineering drawings and info say that the force which is considered the most destructive is the wind lifting the canopy and thereby destroying the alloy frame.
In the notes with the calculations the weight of the actual structure (frame and canopy) are not considered at all because that weight is considered insignificant compared to the upwards force as a result of the wind getting under the canopy and from the aerofoil effect.
The canopy is considered as a enormous aerofoil and, if googled, the lifting force on an aircraft wing comes mainly from above the wing itself. To this end we have stanchions inside the structure which have no function whatsoever in supporting the weight of the canopy, but, are there to prevent the canopy and frame being lifted vertically! And ending up in England.
These stanchions are anchored into further huge concrete blocks with a galvanised steel pin through a galvanised steel "u" section bolted into the alloy section. (Curiously, no provision seems to have been made to reduce the dissimilar metals issue. We do see plenty of moisture what with condensation.)
A similar arrangement exists at the the join between the rafter and the stanchion. On windy days it is usual to see the entire canopy frame lifting an inch or so until constrained by the stanchions. The actual fabric billows a further 8 inches or so in the centres between the rafters.
There is virtually no downward force at all except gravity. However in the winter this problem is reversed so to speak; the snow loading is withstood by tensioned steels rods on the underside of the principal rafters.
This arrangement has been been perfectly adequate for the best part of fifteen years at least, withstanding all the weather on top of Bodmin moor. Whoever designed the anchor system certainly knew their business.
It may be (speculation alert) that the weight of the structure of these other stages was insufficient to resist the lifting and the ground anchors were pulled up by the guy ropes thus decreasing the overall friction of the system.
This post has been edited by ramdram: 01 May 2012 - 10:12 AM