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# Design wind load for a real project by using AS 1170.2

## Design wind load for a real project by using AS 1170.2

(OP)
Hi, I'm confused about the design win load calculation by using AS 1170.2.
This is a real project located in Melbourne suburb Cheltenham.A very typical apartment building.

Building Height: 32.95m from Ground floor to roof
Length:47m width:34m
These parameters are obtained from the structural drawings which I believe are correct:
Importance level 2, Region A5, Terrain Category 3,Vr=45m/s, Ms=1 Mt=1
My parameters:
Md=1 (most adverse condition), Mz,cat=1.012 by linear interpolation, Site speed=45.54m/s
Cp,e=+0.8&-0.65, Cp,i=-0.3&0.2,Ka=1.0, Kc=0.9, Kl=1.5 for positive pressure,Kl=3.0 for negative pressure
Kp=1, Cdyn=1 assume not wind sensitive, a=0.2b=6.4m
Unfortunately my results are quite lower than what the consultant provides. The consultant gives：
ULS pressure +2.62kPa\-2.97kPa <3.4m corner\-2.53kPa>3,4 corner
I asked him why my result is much lower. He only said 'it is vented facade' and refused to talk more about it.

Please help me with it. I don't know which of my parameters are wrong. Could anyone indicate which parameter is incorrect and what value I should use instead?
Anyway I've tried all the most adverse condition parameters but still much lower than his result.
Anybody knows what he means by saying 'vented facade'? Do we generally increase the design wind load by 40%-60% for those vented facade? Does it come from AS 1170.2? If so which clause?

### RE: Design wind load for a real project by using AS 1170.2

Are you dealing with a facade consultant or a structural consultant responsible for designing the major structural elements?

When they start quoting figures for distances away from the corner, I think they would be incorporating the local pressure factors for the design of cladding and immediate cladding supports (purlins, girts, stud framing).

Please note the Local Pressure Factor (Kl) should not be used when designing major structural elements.

### RE: Design wind load for a real project by using AS 1170.2

(OP)
I'm dealing with a facade consultant. Actually we are considering the design wind pressure on windows and sliding doors, not the major structural elements. Any advice?

### RE: Design wind load for a real project by using AS 1170.2

Perhaps he's assuming the louvres on upper mezzanine level create a dominant opening (assuming they are louvres)?

### RE: Design wind load for a real project by using AS 1170.2

If it's windows and doors the Kl factor doesn't apply to internal pressure.
Even so for a side wall corner
Vuz=54.54; quz=1.78kPa
Cp,net=0.2+3*.65=2.15 (SA5 assuming aspect ratio r>1.0)
Cp,net quz=3.84 kPa

Note SA5 only applies if the area is <= 0.25a^2 and only within 0.5a of the edge. However since a=6.4m that still affects quite a bit.

 oops, typo

### RE: Design wind load for a real project by using AS 1170.2

sdz, You've taken a site wind speed of 54.54m/s - it should be 45.54m/s, which produces similar values to what Junyin originally calculated.

Could the facade consultant be assuming the windward wall is permeable as per Table 5.1(A) which would increase your internal pressure coefficient?

### RE: Design wind load for a real project by using AS 1170.2

(OP)
Yea, even assume the windward wall to be permeable, Cp,i will be -0.3 or 0.6 in most adverse condition according to table 5.1A. The result still cannot reach the consultant provides. I'm so confused.

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