scaffold tube strength (1 Viewer)

outward bound

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Hi - i know there are tables in the TG20 mentioning the SWL of tubes with their allowable struts /length. but these are type 4 tube. does anyone know where i can specifications for 3.2MM tube and also black steel tube "meaning tube that is not galvanized - or is it safe to say that this tube has the same capacities as the galvanized tube.

thanks
 
Morning OB
knowing there are tables in TG20 is not enough you need to look at them !!!! :)
TG20-13 Design Guide page 121.122 & 123 may have your answers.
You will also not that the tables are split into two sections "as new" & "used"
The as new will be your Galv & the used will be your black.

Regards
Alan
 
OB you also need to be careful that you know the yield strength of the 3.2mm wall thickness tube that you are using/designing. There are a couple of different types, one is permitted for use in TG20 compliant scaffolds and the other isn't - the TG20:13 design guide has details on this too.
 
OB you also need to be careful that you know the yield strength of the 3.2mm wall thickness tube that you are using/designing. There are a couple of different types, one is permitted for use in TG20 compliant scaffolds and the other isn't - the TG20:13 design guide has details on this too.

The difference in the steels in tables 5.10a & 5.10b is not in their yield strengths - both have a yield strength of 355 N/mm2. Certainly the compliant scaffolds have to use hot 'finished' tube because that is what the guide says. A little while back, it didn't affect the design if you used hot or cold rolled steels but Eurocodes identified that cold rolled steels have a worse imperfection factor and so they give lower design strengths. I think that, given a pair of tubes, one hot rolled and one cold rolled, I can tell the difference but once they are galvanised and being given only one tube, I really don't think that I could tell what I had.

Worse than that, I think that there are stocks of 3.2mm wall thickness tube out there which may not reach 355 N/mm2 yield strength and that would bother me more than the difference between hot & cold rolled. Without testing the tube you have no way of knowing how strong it is. It's just another thing to keep you awake and worrying about at night!!
 
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Thanks TG6 - I think what I was referring to is the EN39 type 3 tube which is the worst of both worlds, low yield and reduced wall thickness and as you say above, there is no easy way to tell the difference. Given that certain far eastern countries who manufacture tube will just stamp whatever you like on it regardless of spec, it is a minefield!
 
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