Serviceability Wind Events...Is it 20yr or 25yr

[asixth]

Hi guys,

Just a quick one. Our office has recently changed our service wind event from a recurrance interval of 20yrs (BCA) to 25yrs (Loading Codes).

This has increased my drift calculations by over 10%!!!

Which is the correct wind event to use and what wind event are others using out there.

 

[OzEng80]

I didn't realise servicability recurrance was covered by the BCA - you should use 25 years.

 

[sdz]

I was under the impression that it was 20 years for servicability, at least that's what is shown in my design criteria. Have you got a reference to support 25 years? I don't have a copy of AS1170.0 to hand.

 

[OzEng80]

It was changed in Nov. 2003 Amendment No 2.

Note that this remains (as it was before) in the 'guidelines for servicabilty limit states'. This leaves plenty of wriggle room under 'engineering judgement'.

Cheers

 

[sdz]

OzEng80,

Do you mean TABLE 3.3 ANNUAL PROBABILITY OF EXCEEDANCE?

All of Section 3 applies only to New Zealand, so that doesn't apply to Australian designs.

SECTION 3 ANNUAL PROBABILITY OF EXCEEDANCE
(FOR STRUCTURES IN NEW ZEALAND ONLY)

 

[OzEng80]

No - I was refering to 'Guidelines for Servicability limit states' Appendix C on page 24.

Cheers

 

[apsix]

OzEng80 is correct.
That's why Table 3.1 'Regional Wind Speeds' added the V25 row.

 

[asixth]

Thanks guys,

That is the table that I was referring to (see attached).

The BCA also has a similar table which I always thought would override any SAI standard, seeing that standards are only deemed-to-have-satisfied documents referenced in the BCA.

I went to an Eng's Australia seminar at the Queensland branch a few weeks ago about designing for Earthquakes to AS1170.4:2007, presented by Prof Wilson from Swinburne Uni, and going by the presentation, I got the impression that annual probability of exceedance periods should be taken from the BCA.

 

[sdz]

asixth, that table says nothing about servicability.

 

[asixth]

sdz,

your right, the table doen't deal with serviceability, I guess I should have looked at the table before I posted it.