Baldrick Posted March 5, 2006 Share Posted March 5, 2006 Hi, I've just inherited a project which involves building two independent lighting towers 30m high, with access to the top (ladders and platforms). The contract states that they can only have a 2.2m x 2.2m footprint, and positioning of guy lines will be problematic because of where it's standing, which is between the front edge of a grandstand roof and a football pitch. Although I am allowed to attach to the adjacent roof at 18m, I'm very concerned about the stability of such a structure. I'd load the bottom of the towers with a few tonnes of ballast but doubt if that alone will suffice. I'm have a meeting with a structural engineer next week to discuss this project on site, but I'd appreciate feedback from anyone who has experience with anything similar. Thanks in advance, B. Link to comment Share on other sites More sharing options...
Seano Posted March 6, 2006 Share Posted March 6, 2006 IMO Layher (or any other kind of scaffolding) isn't the way forward. You need something trussy that can be assembled on the ground and erected by crane in one (or two) pieces. I think you need to speak to either Edwin Shirley Staging or Stageco. (Though it certainly couldn't hurt to ask Roger B at Star about it, he posts here.) Heres an example of the kind of stuff that ESS do:http://deepsoup.f2s.com/goalpost.jpg (I'm the guy standing on the top of the goalpost.) They had some similar sized structures at the Commonwealth Games in Manchester with no guy ropes at all, instead they had rather heavy duty bases and monumental (or just mental) amounts of ballast. Is there a reason you couldn't use truck-mount cherry pickers? hthSean Link to comment Share on other sites More sharing options...
dbuckley Posted March 6, 2006 Share Posted March 6, 2006 I dont know if its common practice elsewhere but what I've seen in NZ is unguyed followspot towers, which look from a distance like a "T". The centre stonk is a square section column with a lattice arrangement , with, as Sean mentioned, a load of ballast (water tanks, usually) at the bottom. Although the tower section is probably about 1m square, the bottom footprint where the ballast is is bigger than 2.2m squared, its about 4m from memory. I've not seen a 30m tall job, but probably 15m. I'm not a rigger or an engineer, but the engineering of these followspot towers does look identical to a tower crane. Since a tower crane tower looks about 2m squared, and regularly go to much greater heights than 30m with quite a lot of weight and stress at the top, maybe that is the answer?? A tower crane is a strong vertical tower with something at the bottom to stop it falling over, usually a lot of concrete blocks. But if the concrets is too big or ugly for your application and the budget is there, and the client willing, then piles into the deck would seem the obvious (and permanent) anchor. Link to comment Share on other sites More sharing options...
klimov Posted March 7, 2006 Share Posted March 7, 2006 That is pretty challenging.. Although 30m structures are quite common with Layer scaffolding (there were a couple of trampolines even higher) this particular tower is going to be something. The highest Layer tower with 2x2 base that I witnessed built was 14 m high and we did attach it to the adjacent wall. It was scary anyway… Rule of thumb here is you can do towers up to 6m with no ballast (taking wind into consideration), up to 10 m with ballast on the ground base. If you have to go higher – attach to the wall somewhere in between or build a bigger base. Without the possibility to attach at 18m – your tower is a dream. Even assuming we are attached at 18 m I would do at least one more ballast point somewhere in between keeping in mind that you are going to have platforms and ladders anyway. Couple of things you have to keep in mind: First 18m would be risky!!! Think carefully how much ballast you are really able to apply on 2x2 base and remember of at least 8 people (700 kg) doing assembling over it. Than think of the evenness of the surface beneath the tower (the smallest angle would increase dramatically over 30 meters) and what kind of surface it is. I am afraid nothing but concrete will work and if the amount of ballast is inappropriate, together with people and windload it make the whole tower collapse. How tight it is possible to attach the tower – obviously the tighter the better.How many workers you are going ho have - you’ll need a least 15…. The bottom line is that if you do that (with no gaylines and base no bigger than 2x2 ) and survive the event intact you’ll be unique enough to apply for Guinness book. Let me have a picture than… Cheers Link to comment Share on other sites More sharing options...
Seano Posted March 7, 2006 Share Posted March 7, 2006 A tower crane is a strong vertical tower with something at the bottom to stop it falling over, usually a lot of concrete blocks.I've seen tower cranes with "loose" concrete block ballast on a steel base, but I think the "standard" ballast for a tower crane is actually a single concrete block - rather a large one, poured and cast on site and reinforced in such a way that it actually forms the base of the tower. I think the weight is generally of the order of hundreds of tons. Obviously the mast of a tower crane has to withstand higher bending moments than a lighting tower though. I had a little browse around Stageco's website, and found a couple of quite interesting things. This especially:http://www.stageco.com/newsite/uploads/6781_scaff-TW2004-IMG_0294-480x360.JPG It looks like a big tall Layher tower, but cunningly it has a tower truss "spine" up the middle. Its concrete ballast blocks are confined within the footprint of the Layher, but I suspect the truss has one of their standard bases - a rather larger but quite low profile steel structure with integral tanks for water ballast. If you look closely at the bottom right of the picture I think you can see it under the stage. Seanx Link to comment Share on other sites More sharing options...
Baldrick Posted March 8, 2006 Author Share Posted March 8, 2006 Hello all, and thanks for the replies and cool pictures. The towers are to stand for 11 months, ruling out the cherry picker, and the end customer is a construction company who own at least 50 cranes in the 30m+ category, which I found strange myself. However, the plan I've been sent is completely different to what I was asked for, standing on a 10.6m x 4.6m footprint which is to be built back into the grandstand with lots of ballast. The grandstand is closed to the public and is being reinforced for the occasion. The final 10m of the tower will be 2 fields wide, and will standing on 6 x 20m 'Quad' standards with guy-lines left and right. Even the bit about the platforms was wrong - the customer insists that personnel will climb the structure with a double lanyard in the event of any service work - no ladders and no platforms! If I end up on site with this then I'll post a couple of pictures, in the meantime, here is a link to the bottom of a 'Quad' standard, rated to 16t. http://img115.imageshack.us/img115/7981/quadbase0fq.jpg Thanks again for the ideas, B. Link to comment Share on other sites More sharing options...
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