Revised internal pressure calculation in AS/NZS 1170.2:2021 Part 2

[Tomfh]

This is a follow up from the following thread:

Revised internal pressure calculation in AS/NZS 1170.2:2021? - AS/NZS (au/nz) Code Issues

In the recently revised wind code, there is a change to the way internal pressures are calculated for structures with dominant openings. The 2011 version defined the internal pressure coefficient as the external pressure coefficient at the location of the opening [i.e. Cp,i = Cp,e at the...

www.eng-tips.com

In it, someone asked:

For the Kl part, is it still only referring to cladding, cladding fixings, elements that supports cladding, and this fixing?

to which @rowingengineer replied:

For KL internal pressure it applies to all parts of the building. This has been clarified by the code committee.

Can anyone confirm/clarify this? Are local pressures at the locations of openings now applied to all internal surfaces simultaneously, including loading of primary framing members?

 

[rowingengineer]

The local pressure factor is ment to represent the external local pressure factor acting on the opening at the max event. There was a fair bit of testing done and a thesis was born and it does suggest that you are correct, the local variable pressure is still present with an opening. I think the guy was Mitchell.

However what the code didn't take from the testing was the flexibility of the structure.

 

[Tomfh]

Do you have any references? I can't find anything by Mitchell?

 

[human909]

You mean this video:

I thought it was Chris h on the NZ video where we asked but I can't find it ont hat video, but we asked one of the committee members during the presentations to clarify the intent.

The question was asked here too, but noanswer wasn't given:

What do you mean from how physics would work? I’m trying to understand, but it seems contradictory with what local pressures represent.

Local pressure factors represent short, localised spikes due to turbulent corner flow, enough to damage cladding, but not the structure. So how can that same brief pressure spike (say kL= 1.5,2,3), once inside, load the entire internal volume and frame? Where does the extra energy come from to do all that work, if it wasn’t present to begin with? Do the flow dynamics change radically if there’s an opening, with the local pressures persisting in the location of openings?

My gut feeling is to agree with you. Though my understanding is that local pressure are not necessary all "brief pressure spikes" eg corners. But I still generally agree with your thesis

However I have questions:
-Would air flow as is required to increase the pressure inside the building be sufficient and not affect the actual pressure at the local source? Unlikely IMO/
-Would the volume of the airflow required be sufficient to given buildings are leaky and cladding is flexible?