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RE: StructuralPedia - Main Wind Force vs C&C Wind Force

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How would I go about contrasting that with the local pressure factor
(kl)approach of AS1170.2, to add international context?

Here we don't really differentiate between MWFRS and C&C. Given the C&C
approach of ASCE7-05, and the research, there is an implication that maybe
we should probably be applying the local pressure factor in a lot more
situations. For example local pressure factor would be applied to roof
cladding and support batten, but not to any part of the roof truss nor
rafter. Nor to a wall stud. The validity of the approach is reinforced by
the timber framing code AS1684 and its accompanying structural model
AS1684.1. More over the truss or rafter and wall stud would be subject to an
area reduction factor (ka), and a load combination reduction factor (kc).
Most recent revisions to our code, seem to tend towards more ways of
reducing the wind loads not increasing. Maybe we should be tending towards
increasing loads.

On the other hand investigations after tropical cyclones tends to indicate
the code is providing adequate strength. The main changes have been improved
testing of steel cladding profiles for cyclonic conditions.

It seems our respective code authors have different philosophies regarding
risk, and accounting for extreme pressure coefficients: though neither of
our codes account for the Cp=-20 apparently recorded at Texas Tech full
scale building experiments.

Conrad Harrison
B.Tech (mfg & mech), MIIE, gradTIEAust
South Australia


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