TG20:08 Safe Height Tables No Longer Valid

BMB

BMB

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Hey all,

Upon a browse of the NASC website after reading their 2012 yearbook I came across this in a new article:

Due to the impending review of TG20:08 Volume 2, which is necessary following the introduction of the European Wind Code and the publication of BS EN1991-1-4:2005 A1:2010 (European Wind) and the National Annexe to BS EN1991-1-4:2005 A1:2010, all the safe height tables, text and diagrams associated with wind loading covered in TG20:08 Volume 2 are no longer valid and the tables detailed below should not be used, with immediate effect:

Tables being reviewed:

Table 29 – 31 (Pages 154 – 159)
Safe heights for Basic independent tied scaffolds fully ledger braced with fully loaded inside boards.
Table 34 – 36 (Pages 165 – 168)
Safe heights for Basic independent tied scaffolds part ledger braced.
Tables A1 – A24 (Pages 172 – 219)
Appendix A - Tables of maximum safe eight for fully ledger braced Basic Scaffolds
Tables B1 – B12 (Pages 222 – 233)
Appendix B - Tables of maximum safe height for part ledger braced Basic Scaffolds with line of ties at alternate lifts.

The NASC are currently reviewing the data associated with the wind load calculations and intend to issue revised data shortly. Until this time the NASC advises all users of TG20:08 - Volume 2 that the safe heights identified in the tables mentioned above will have to be determined from first principles.

Immediate questions that spring to mind:

1. Are the NASC saying that all the scaffolds covered in these tables need to be designed?

2. The switch to Eurocode 1991-1-4 (and the withdrawal of BS 6399) happened at the beginning of 2011.. what have we been doing for the last 10.5 months then?

The news article on the NASC website can be found here: TG20:08 Technical Scaffolding Guidance on the use of BS EN12811-1
 
Training people on the wrong info looks like. Are there any other changes from europe we dont know about???
 
BMB said:
Hey all,

Upon a browse of the NASC website after reading their 2012 yearbook I came across this in a new article:

Due to the impending review of TG20:08 Volume 2, which is necessary following the introduction of the European Wind Code and the publication of BS EN1991-1-4:2005 A1:2010 (European Wind) and the National Annexe to BS EN1991-1-4:2005 A1:2010, all the safe height tables, text and diagrams associated with wind loading covered in TG20:08 Volume 2 are no longer valid and the tables detailed below should not be used, with immediate effect:

Tables being reviewed:

Table 29 – 31 (Pages 154 – 159)
Safe heights for Basic independent tied scaffolds fully ledger braced with fully loaded inside boards.
Table 34 – 36 (Pages 165 – 168)
Safe heights for Basic independent tied scaffolds part ledger braced.
Tables A1 – A24 (Pages 172 – 219)
Appendix A - Tables of maximum safe eight for fully ledger braced Basic Scaffolds
Tables B1 – B12 (Pages 222 – 233)
Appendix B - Tables of maximum safe height for part ledger braced Basic Scaffolds with line of ties at alternate lifts.

The NASC are currently reviewing the data associated with the wind load calculations and intend to issue revised data shortly. Until this time the NASC advises all users of TG20:08 - Volume 2 that the safe heights identified in the tables mentioned above will have to be determined from first principles.

Immediate questions that spring to mind:

1. Are the NASC saying that all the scaffolds covered in these tables need to be designed?

2. The switch to Eurocode 1991-1-4 (and the withdrawal of BS 6399) happened at the beginning of 2011.. what have we been doing for the last 10.5 months then?

The news article on the NASC website can be found here: TG20:08 Technical Scaffolding Guidance on the use of BS EN12811-1
Click to expand...

I've been waiting for your comments on this.
 
Aha I was just going to shout.... Simian!!! Does the nasc and europe not collate anything? (Before publication)
 
Thats the technical committee that gets involved in this, not my bag
 
I have to make one additional point...

The Eurocode 1991-1-4 was released in 2005.. and became mandatory in January 2011 when BS 6399 was withdrawn.

When TG20:08 was released at the end of 2008.. first question: why is wind loading not to Eurocode?

Would have avoided this situation entirely.

---------- Post added at 03:23 PM ---------- Previous post was at 03:18 PM ----------

Simian - surely these questions need to be answered by the NASC tech committee? Afterall, they are responsible for the publication of TG20. Are there any rumours from within NASC that they will publish any clarification?
 
Not sure Ben, i will give them a shout though as you are not the first, they do say resort to first principle. However i know its being revised to be launched in 2013 as a much easier user friendly document with a lot more designs in.

Ian
 
FYI.

Dave Chapman from the NASC just called me back - he was pretty helpful and honest about everything, he said:

1. The scaffolds covered in those tables need to have calculations.
2. Scaffolds currently standing erected to those table's would not become invalid in retrospect.
3. The issues would be discussed on Friday at the NASC officers meeting and clarification would follow, most likely to be sometime next week.
 
More money to spend for a file that is full of mistakes in 2013 then ?
Simain you said you have been waiting for this one ? Have you been training lads to that info ? Even though you know it's wrong ?
 
it's those clever people form the Brussels again I'm afraid, they can change the wind speeds now, pity they didn't have any regard to the already mounting legislation we have to adhere to from these euro dictators, and consider the amount of disruption and cost they are creating on nothing much more than a whim.
 
Current tables withdrawn with immediate effect: What will you be working to now?
 
Easy answer we always train to the current standards however for scaffold courses we focus more on TG20 volume 1 and the supplement of tables that came out earlier this year. For volume 2 we always explain Its more for designers, I am on my second volume 1 but I have to blow the dust off volume 2 once every three months like everyone else but the designers.

Ian
 
Nice to know Cads were already on the case if you pardon the pun. I will have to give them a call to make sure but looks like I may be ahead of the game already.:cool:
 
XxIANxX said:
http://www.scaffoldersforum.com/scaffolders-forum/4436-wind-speed.html

Andy look at the date of when I started this thread , they have known for some time.
Click to expand...


Ian we have known alot longer than September that the wind loads in TG20:08 were no longer any good more like 6-8 months. It does baffle me as to why it has taken so long for a proper statement to be issued.

im well pissed off now as:

Manchester, 10km From Edge Of City Surrounded By Buildings Upwards Of Wind (Wind Speed Table)
Halfway Up A Slope Of 1:18 (Topographical Factor)
Altitude: 60m
Scaffold Designation: 3-5-2 Fully Boarded (Table 1)
Debris Netted. Ties At Alternate Lifts (Table 3)

Wind Speed, (Vb) = 22m/sec
Topographical Factor: T = 1.13
Altitude: A = 60m

S = Vb x T x (1 + ) = 22 x 1.13 x (1+ ) =

22 x 1.13 x 1.06 = 26.35 = 26 = Safe Working Height Of 13m


is my favourate calculation going into the office in a morning.
 
scaffoldingsafetyservices said:
Ian we have known alot longer than September that the wind loads in TG20:08 were no longer any good more like 6-8 months. It does baffle me as to why it has taken so long for a proper statement to be issued.

im well pissed off now as:

Manchester, 10km From Edge Of City Surrounded By Buildings Upwards Of Wind (Wind Speed Table)
Halfway Up A Slope Of 1:18 (Topographical Factor)
Altitude: 60m
Scaffold Designation: 3-5-2 Fully Boarded (Table 1)
Debris Netted. Ties At Alternate Lifts (Table 3)

Wind Speed, (Vb) = 22m/sec
Topographical Factor: T = 1.13
Altitude: A = 60m

S = Vb x T x (1 + ) = 22 x 1.13 x (1+ ) =

22 x 1.13 x 1.06 = 26.35 = 26 = Safe Working Height Of 13m


is my favourate calculation going into the office in a morning.
Click to expand...

That's a volume one calc, they are all changed
 
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