TG20 Compliance Sheet

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TG6

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I've been given a compliance sheet which notes:

Wind Factor 20.0 (low wind exposure)

Two questions:

If Wind Factor = Twind x Calt x Vb,map with Twind always greater than 1, Calt always greater than 1 and Vb no lower than 21.5, how does TG20 get a wind factor of less than 21.5?

At what Factors does low wind exposure give way to moderate and then to high?

I know that I can factor down for season, duration, possibly size factor etc but Wind Factor seems to be defined before these are applied and, as far as I can tell, these aren't included in the TG20 compliance sheet computation anyway.

Tim
 
It seems to take a wind factor of 20 for anywhere in the interior of England, jumping to 21 for places like Blackpool on the coast. It hits 22 for Scotland. Maybe it was just easier to program that way. I don't know.
 
"If Wind Factor = Twind x Calt x Vb,map with Twind always greater than 1, Calt always greater than 1 and Vb no lower than 21.5, how does TG20 get a wind factor of less than 21.5?"

^^^^^^^^^^^Tim, i think your keyboards broken matey^^^^^^^^

:D :D
 
copperknackers said:
"If Wind Factor = Twind x Calt x Vb,map with Twind always greater than 1, Calt always greater than 1 and Vb no lower than 21.5, how does TG20 get a wind factor of less than 21.5?"

^^^^^^^^^^^Tim, i think your keyboards broken matey^^^^^^^^

:D :D
Click to expand...

I think you could be right - I know I'm broken.

---------- Post added at 04:16 PM ---------- Previous post was at 04:07 PM ----------
Nick-CDS said:
It seems to take a wind factor of 20 for anywhere in the interior of England, jumping to 21 for places like Blackpool on the coast. It hits 22 for Scotland. Maybe it was just easier to program that way. I don't know.
Click to expand...

If it comes out with a printed figure of 20 which is clearly wrong, can you trust anything else? I suspect that you will get higher figures on higher ground and way up north or west or for higher scaffolds but again if what you are finding is 21 where it should be a minimum of 23.5 & 22 where you'd expect 25 or more, what value is the rest of the sheet?

It makes compliance sheets not worth the paper they are written on doesn't it? Of course, I may be missing something because I can't believe I am the first one to see this - surely any recipient of a compliance sheet is going to check it, aren't they? If people start looking at them, there could be a load more work for designers.
 
You can choose the season as you input the compliance sheet, which if it's the 6 month summer season would introduce a factor of 0.84, meaning you could end up with a wind factor below 21.5.
 
Have you run a hand calc for the same tie configuration and location? If the sheet is way off the calculated load, that's a big issue.
 
biffo0911 said:
You can choose the season as you input the compliance sheet, which if it's the 6 month summer season would introduce a factor of 0.84, meaning you could end up with a wind factor below 21.5.
Click to expand...

I have asked for a check on that but apparently changing the season makes no difference to the wind factor and the minimum always comes out at 20(apparently the default season is winter rather than 12 months - a bit random just like the default location being somewhere in the country near Halifax). I can't find any mention of the season on the compliance sheet or in fact the location - am I missing those as well?
 
That is one of the issues with the compliance sheet - it doesn't include the postcode or details of what has been entered, meaning you need to basically do it from scratch yourself in order to check that the details have been correctly entered if you are checking it.
 
Hmmmmm. And it costs how much?
 
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