motorcrazy Posted January 14, 2007 Share Posted January 14, 2007 I have some expereince working with 4 corner truss supports to a roof structures. Do you concider the roof as a mother grid, and attach the motors to this grid. But when rigging outside you have a wind load acting on the roof. Does it matter, I'm sure they would do a 5:1 SF on the total structure it self. I know these structures can hold alot of static weight. What I was looking for is someone with a good amount of time working with these structures to go through a design. 90% of my work is indoors and the other 10 is with scaffold towers and stages. Later Rick Link to comment Share on other sites More sharing options...
slipstream Posted January 14, 2007 Share Posted January 14, 2007 Stop asking these questions - you are starting to scare me - you should not be creating hanging rigs unless you have the knowledge to do so safely. A roofs safety margin in the UK particularly is based on the possibility of having a 4' snow load across the whole structure, hanging 3 tons from one end of an internal cross brace was not uppermost in the designers mind. Some really substantial roofs can only take a 1ton load if the motor is braced across 2 or more internal members to I can rig hanging points with the best of them but only after someone with the qualifications said the hang points are rated for the proposed load. It is easier than you would think to bring a large span roof down or damage it enough to require replacement. You really need to get in tow with someone locally who is qualified, there are a load of freelance riggers who you can hire in - they are not interested in equipment supply - just their daily rate so they are not in competition to you. Sam Link to comment Share on other sites More sharing options...
StevieR Posted January 14, 2007 Share Posted January 14, 2007 Stop asking these questions - you are starting to scare me - you should not be creating hanging rigs unless you have the knowledge to do so safely. Err, Sam... I think that's exactly what he's looking for. If you re-read the OP he says.. What I was looking for is someone with a good amount of time working with these structures to go through a design. If that is not admitting your own lack of knowledge and seeking external experience and input I don't know what is. Link to comment Share on other sites More sharing options...
ed_ Posted January 14, 2007 Share Posted January 14, 2007 A roofs safety margin in the UK particularly is based on the possibility of having a 4' snow load across the whole structure, Are you talking about temporary or permanent structures here? I've seen design documents for a roof structure that is in regular use in the UK that specifically exclude snow loading. I am not an engineer, but... Every temporary structure sets a limit for the maximum wind speed allowable before the structure must be dismantled (dismantling a roof structure in wind that high is not something I'd particularly enjoy, however the use of 'blow-through' panels in the side skins, or removing the skins entirely, may prevent this necessity) - is anyone aware of a standard design wind speed for temporary structures? Engineers designing permanent structures calculate specific wind loads based on the wind speeds likely at the site the structure is to be built on, but temporary structures don't have that luxury... Link to comment Share on other sites More sharing options...
slipstream Posted January 14, 2007 Share Posted January 14, 2007 Does it matter, I'm sure they would do a 5:1 SF on the total structure it self. I know these structures can hold alot of static weight. I am pretty sure it matters - the safety factor is there for a reason and should not be eroded by a rig the buildings designer did not allow for. Sam Link to comment Share on other sites More sharing options...
trussmonkey Posted January 15, 2007 Share Posted January 15, 2007 you should always refer to the manufacturers guildlines when using motors/trussing. they will give you all the relevent info you need. if your not sure about your figures then you should ring them or get someone more qualified to do the job. Link to comment Share on other sites More sharing options...
RogerB Posted January 29, 2007 Share Posted January 29, 2007 I have some expereince working with 4 corner truss supports to a roof structures. Do you concider the roof as a mother grid, and attach the motors to this grid. But when rigging outside you have a wind load acting on the roof. Does it matter, At the risk of sounding belligerent, of course it matters! I would go so far as to say there is not a rigger in the UK that knows how to work out the wind loads on a temporary outdoor roof system. If you disagree, send us a CV and we'll give you a job! We have loads of outdoor roofs. The last one we checked cost us over £25,000 in structural engineers fees and the spreadsheets they produced to get to the answer(s) were over 240 Giga-bytes! It is a complex subject and if the equipment you have does not come with a huge file giving you chapter and verse on all the wind load issues associated with it, then it is not 'fit for purpose' for outdoor use. Keep it safe - stay indoors! Best regards RogerB Link to comment Share on other sites More sharing options...
Paul Jordan Posted February 26, 2007 Share Posted February 26, 2007 Bingo.... well said Roger BR Paul Link to comment Share on other sites More sharing options...
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