AS2870 and AS1170.2 - 2011

[OzEng80]

New additions have been released in case you didn't receive notification from SAI (like me).

 

[rscassar]

What do you think of the new revisions?

 

[OzEng80]

Hi kikflip

I haven't had a good oportunity to look through the codes yet but initial impressions are:

AS1170.2
Appears to be more of clarification than anything and addresses some common points of confusion/contention.
2.5.7 Debris loading is a function of Vr and is clearly defined (these values look familiar and I think were part of a ‘cyclone shelter’ design manual).
5.3.2 Openings and internal pressure coefficients seem clearer (most of my designs are region C so it has always been pretty straight forward!). The 25m height limit for debris is good. I am bemused by the note under 5.3.2 regarding garage doors designed to AS4505 being able to be treated as closed and intact – ie capable of resisting debris loading?!
5.4.3 Excellent clarification and diagrams for Kc
5.4.4 Increasing the upper limit of Kl to 3.0 for corners of roofs and the upper limit of Cpe x Kl to 3.0 is nasty and will be extremely difficult to put into practice. Much better diagrams.

AS2870

I haven’t had time to look through this although I went to a course last year where they advised what was coming. It’s my understanding that a lot of the typical designs get worse and now we are obliged to give direct and site specific consideration to trees (can’t just rely on the CSIRO disclaimer).

I will update this once i get a chance to put them into use (and all the gremlins come out!).

What are your thoughts?

 

[rscassar]

AS1170.2 also specifically spells out a 0.9 kc factor for windward+ leeward combination

 

[csd72]

OzEng80,

I thought that standard would be similar to how the large industrial doors worked but I was not sure so I did a aquick google.

http://hia.com.au/hia/content/Build...mestic Garage Door Installations AS 4505.aspx

Looks like these doors have a lock in track along each side and are designed to act as a catenary between.

Not in the description of the code that it also notes the loads that the structure has to be designed to take.

This is definately something that the structural engineer would need to be involved in the specification and checking of.

 

[OzEng80]

We butt heads with roller door manufacturers all the time over this. Catenary loads from windlocked systems are massive and are generally orientated about the weak axis of the primary structural elements. Can be a real headache (& that is after turning a blind eye to 'corner' configurations!). It is one thing to say that a roller door (working as a sail) can resist cyclonic loadings but a completely different thing to say that it is resistant to debris loadings (as implied).

I am assuming that the argument used is that the impact testing done by Lysaght for custom orb and trimdek can be extrapolated to door configurations. This seems like quite a stretch given that the testing was based only on the 100x50 at 15m/s for a 900 sheeting span with screwed side laps. With the new code doubling the speed of impact and introducing 'ball bearings' i don't know how this can be justified.

What do you think of the Kl = 3.0 for roof corners?

 

[csd72]

Yes, I can see that this is going to cause issues, particularly for overhanging corners.

It would be interesting to see the statistical justification for this in the commentary.