Studding or round slings?

[uponepar]

Hi there,

 

Had to create a new account due to forgetting old login credentials.

 

I'm posting on behalf of a church, as I've recently had a look at their current setup and I'm not quite sure whether I like the looks of it so I thought I'd post on here to see what people thought.

 

The building is a converted parachute factory with a steel apex roofing structure (think of an A) there is a false ceiling just below the horizontal bracing in the 'A' and IWB's hung below that.

Currently the IWB's are hung using two stud bolts (one at each end) on the 'A's where they come through the ceiling either side, however the bars are fixed at 90degrees to the studding, so the strain is essentially running across the bolt rather than along it (if the load were to be hung vertically from it) there is also a steel safety in the middle to stop the IWB from sagging.

 

My question is; would it make more sense to use say 4 means of support (steels or round slings) to evenly support the weight of the IWB from the horizontal girder above the false ceiling rather than the studding?

 

Theres about 200kg of weight on each bar and it would be useful to make up a iwb grid and suspend it evenly rather than the current IWB's supported on their own.

 

Thanks in advance.

[Tom]

How long are the IWBs and what are they made from?

 

If the "steel safety" is stopping the bar sagging then it's not a safety its a means of support.

 

There's nothing wrong with using studding (assuming it's the correct studding and correctly attached) but, depending on the length of the bars - and I'd have thought they were a good length to be doing what you're suggested - I'd want to see more points on them.

 

Having said all that - the answer you're going to get from everybody is get somebody in who knows what they are doing to look at it and advise you properly. It doesn't have to be expensive. Do you know who put the bars up there in the first place?

 

T

[kerry davies]

I would recommend getting an expert opinion.

Very often A frame ironwork has no loading capacity and is roof supporting only, particularly in older buildings though even brand new ones sometimes fail to include the ability to carry suspended loads in their design calculations.

 

I think it highly unlikely that anyone could offer a sensible opinion without first inspecting the roof trusses. The horizontal members in A frame trusses are tension members rather than load bearing and I know of at least one brand new building that had no SWL capacity designed in.... and that was a dedicated events space which had to be sorted out by structural consultants.

[uponepar]

How long are the IWBs and what are they made from?

 

If the "steel safety" is stopping the bar sagging then it's not a safety its a means of support.

 

There's nothing wrong with using studding (assuming it's the correct studding and correctly attached) but, depending on the length of the bars - and I'd have thought they were a good length to be doing what you're suggested - I'd want to see more points on them.

 

Having said all that - the answer you're going to get from everybody is get somebody in who knows what they are doing to look at it and advise you properly. It doesn't have to be expensive. Do you know who put the bars up there in the first place?

 

T

 

 

They are 6m Annodite Ally IWB's. Yes, sorry the steel in the middle is means of support as I believe these IWB's need support every 1-2m hence why they are there.

 

I think I'd just feel safer using 4 round slings per IWB to between it and the girder above. So I suppose my main question is; Is it okay to use round slings or is there a requirement that permanent installs need steels etc. Although having said that I shall still get a structural engineer in to see whether the girder is able to support weight.

 

I would recommend getting an expert opinion.

Very often A frame ironwork has no loading capacity and is roof supporting only, particularly in older buildings though even brand new ones sometimes fail to include the ability to carry suspended loads in their design calculations.

 

I think it highly unlikely that anyone could offer a sensible opinion without first inspecting the roof trusses. The horizontal members in A frame trusses are tension members rather than load bearing and I know of at least one brand new building that had no SWL capacity designed in.... and that was a dedicated events space which had to be sorted out by structural consultants.

 

 

 

Thanks for your advice, I shall have a structural engineer in to have a look at the roof structure. As I said the building was a parachute factory and had parachutes hung from the roof for drying, so it'd be worth someone having a look.

 

Thanks

[Brian]

...Is it okay to use round slings or is there a requirement that permanent installs need steels etc.

Think about what happens in the event of a fire.

[TomM]

...Is it okay to use round slings or is there a requirement that permanent installs need steels etc.

Think about what happens in the event of a fire.

 

The aluminium ferrel on the steel wire rope melts, causing failure? (I can't remember the fail temperatures, but I think it is a little higher for a round sling - though not by much!)

 

T

[Seano]

It does sound like the current installation is a bit smelly, to say the least.

 

As Kerry says, the horizontal part of the "A" is essentially there to provide tension. Sometimes they are rigid enough to take a bit of load though, and 200kg distributed across the roof truss doesn't sound like much in the scheme of things. (Though I'm not totally clear if that's the load on the bar now or the SWL you'd be looking for from your shiny new one.) If the horizontal member isn't good for it, its quite likely that the top of the roof truss will be.

 

No point me guessing about that here though. Its good that you're getting someone in to check that out.

 

Studding would be fine, though obviously it should be vertical. If you're wanting to clamp it to the flange of a non-horizontal beam (or angle-iron, 'T' iron etc..) there are 'swivel' units to go with Lindapter flange clamps.

 

Personally I wouldn't be keen to use polyester roundslings, I'd probably prefer steel wire ropes made to measure (for example by Rope Assemblies). As much as anything just because it looks so much better.

 

The "what happens if there's a fire" thing is indeed a bit overstated imo, at least as far as the whole building being on fire is concerned. Possibly not so much in the case of a small localised source of heat though - if you really want to you can provoke a polyester sling into failing with a cigarette lighter or a soldering iron. (Or, more to the point, an idiot could just about do it with a smallish gerb.)

 

When you say 'grid' are you thinking of also having bars perpendicular to your roof trusses?

The question that springs to mind there is what is the span between them, and will your bar be adequate?

You might have the option to bridle between the tops of your roof trusses to contrive an intermediate support. Something else to discuss with your structural engineer perhaps.

[kerry davies]

Answer really is neither, but to use studding and appropriate tube brackets, if I am following this train of thought correctly.

 

If the only thing they hung were parachutes then I would definitely get the load-bearing capabilities assessed. You can get a hell of an expanse of silk in 200Kg and you may already have a fair weight of suspended false ceiling hanging off it.

 

Crosspost with Seano who is talking sense. You may need a grid designing as well as load assessment.

[ramdram]

Agreed on the above caveat stuff but first of all uponepar might be better advised to stroll into his local authority office and have a natter with the building control office bods and set out his stall. It may be they know the building, presumably because of change of use, say, or during the conversion process.

 

With any luck they may even have the structural plans/specs on file so could advise on what "they" want to see before any "works to" starts. We're talking fire precautions...proofing(?)...loading issues such as RSJ(s) across the void...could be anything. Might even require an RSJ goalpost type arrangement, with double fire resistant plasterboard sheath, who can say?

 

 

If you are extraordinarily fortunate then the existing structure may have been over engineered and you could hang any number of IWBs without any issues at all. Might just have to have a look around Flints for example to sort out suitable hardware.

[Seano]

You can get a hell of an expanse of silk in 200Kg

Very true, it is rather the point of a parachute to be floaty-light. ;)

Though even if they'd hung heavy things from the roof to dry back in the day, there'd still be no guarantee they weren't pushing their luck!