AS 1576.1 AS 1170.0 Queries

[ghecks]

Hi All

First time poster, bare with me.

I am having great difficulty trying to determine some appropriate figures for wind loads for use in scaffolding.

I do not currently have access to BCA (not sure if an issue)

For one, i cannot find information pertaining to the importance level, so i am assuming 2 for this.

Secondly, I cannot seem to find any reference with regard to calculating the Ws (serviceability design actions). Wu ultimate is basically what i am using to design for. If have seen that 1170.0 throws you to 1170.2 and vice versa, but no definitive figure or formula is given.

AS1576.1 basically states that the annual exceedance for wind is 1/100 leaving me with a Vr of 48m/s.

There is no allowance for serviceability or design life of structure which may be as little as a month.

I believe i am using a very conservative approach at the moment but also think too conservative.

If anyone has any experience with calculating wind loads on scaffolding (short design life) it would be very much appreciated if you could help me on this.

regards

 

[apsix]

You are correct, Vr is determined from AS1171.2 Table 3.1.

For working life < 6 months, non-cyclonic APE is 1/100 for Ultimate LS.
For SLS it's typical to use APE = 1/25, as per AS1170.0 appx C.

 

[ghecks]

Thanks for the response apsix

I just somehow find it a little excessive designing scaffold to withstand 170km/hr winds when the site would have its own maximum allowable working wind conditions, which would basically turn this structure at that point into an importance level 1 by my book, i.e no one being on site, no risk of injury. (obviously this depends on the location)

The big thing here i believe is that scaffold can be dismantled if "very" inclement weather is approaching so therefore i do not see the need do design to such high speeds.

I guess i will wait and see if any codes are updated to allow for this kind of thing.

 

[rowingengineer]

Note at the back of As1170 there is the non bca items listed, for region C and D the approprate return period is noramlly 1:200.

http://www.nceng.com.au/

"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected” Petroski 1992

 

[rowingengineer]

Also it is not just weather your structure is at risk, you also need to consider what other structures would be at risk. Debris generation is a key consideration here, long steel pipe have been known to cause serious damage during cyclones.

http://www.nceng.com.au/

"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected” Petroski 1992