waystation Posted November 13, 2015 Share Posted November 13, 2015 J.C. Joel's of Halifax have fitted us with a new grid. S.W.L. = 1.5 ton.After condemning old timbers as unsafe, they have attached UNISTRUT to old structure. I'm uncertain as to whether it is safe, and am not senior enough to force another check through.What can I do ?Stage is 20' x 40' and grid is 20' up. We've got a lot of children under it. Link to comment Share on other sites More sharing options...
Bryson Posted November 13, 2015 Share Posted November 13, 2015 What about the system leads you to think it's unsafe? Is it the underlying structure you think is the problem or the new installation? Why did you emphasize the use of Unistrut? While you should always have an eye on safety and ask questions, Joels are a reputable company that I'm sure aren't new to this kind of installation. Link to comment Share on other sites More sharing options...
waystation Posted November 13, 2015 Author Share Posted November 13, 2015 What about the system leads you to think it's unsafe? Is it the underlying structure you think is the problem or the new installation? Why did you emphasize the use of Unistrut? While you should always have an eye on safety and ask questions, Joels are a reputable company that I'm sure aren't new to this kind of installation.(1) While fastening new fittings to 8" timber, holes have been drilled for bolts at only 1 1/2" from lower edge. I can make movement of over an inch in structure with only hand pressure ( I'm not talking about swinging of it here - just the sort of wiggle you might give from the top of a ladder). (2) it is the fixing of new, to a structure they previously said was unsafe that first made me think. (3) Unistrut emphasized only to indicate brand name. And, yes, I understand Joel's reputation and am not saying they are negligent. But wanted to show that this wasn't done by cowboys. Link to comment Share on other sites More sharing options...
ImagineerTom Posted November 13, 2015 Share Posted November 13, 2015 If you post pictures then members here could give you their thoughts and comments BUT that's all they would be. If the grid has been "certified" to a certain SWL then there should be some paperwork somewhere telling you how that figure was determined (sums or actual tests) and what the parameters were that they assumed when making that certification. You need to cross-reference that information against the actual use and forces applied to your grid and then see how the data compared. Bolting re-enforcing to something is a very common method of increasing the strength of a structure so is not in and of itself "wrong" Link to comment Share on other sites More sharing options...
paulears Posted November 13, 2015 Share Posted November 13, 2015 the SWL of the grid at 1.5t? If this is a figure for the entire thing, as in all the things being hung from it, then individual suspension points might be correspondingly even lower. In my old college, Stage electrics hung our permanent staff grid from the Victorian Timbers, using coach bolts - a horizontal fixing through a solid piece of timber can suspend surprising loads. You commissioned them to install these things for you, assuming the paperwork is in order, I personally would not worry. Link to comment Share on other sites More sharing options...
kerry davies Posted November 13, 2015 Share Posted November 13, 2015 Rather than take this any further on an open forum I suggest you take this up directly with your suppliers, who have a reputation to protect. (Nudge, nudge. Say no more.) Nobody here can offer an informed opinion, even with photographs, and would need to see the items you have difficulty with in person. For example "timber" might be a soft pine joist or a piece of ancient oak that is harder than titanium steel. Link to comment Share on other sites More sharing options...
adam2 Posted November 15, 2015 Share Posted November 15, 2015 In view of the reputation and experience of the company who did the work, I would agree that it is probably fine. If however doubts still remain, then it should be simple enough to get a second opinion from an experienced structural engineer. Link to comment Share on other sites More sharing options...
Ynot Posted November 15, 2015 Share Posted November 15, 2015 If however doubts still remain, then it should be simple enough to get a second opinion from an experienced structural engineer.Second opinion shouldn't be needed at this stage - just a clarification from Joels. If you're not 'senior enough' to do that, then your responsibility if YOU have doubts is to pass those doubts up to someone who IS senior and ask them to ask the questions. Link to comment Share on other sites More sharing options...
Dave m Posted November 15, 2015 Share Posted November 15, 2015 When I worked in a relatively new civic theatre complex we had an issue when suddenly somebody discovered that the entire grid was held up by relying on bolts threaded up through wooden timbers in the loft space above the grid. There were no washers anywhere and remedial work had to be carried out asap even though at that time the building was about 5 years old. The entire grid was pulling itself through the rather flimsy wooden structure above.Where I am now we have threaded studding of some sort that was ( I think) cast into the building somehow. Link to comment Share on other sites More sharing options...
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