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AS/NZS 1170.2: Local Pressure Factor for SLS

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micks87

Structural
Feb 10, 2014
16
Hi All,

A few engineers in my practice have different views of using KL factors when designing roof purlins.

No doubt, the code ask for kl factors to be checked when assessing the ULS capacity of the purlins.

What about for SLS? We have had situations where we have had a kl of 1.5, and as a result our purlins fail in serviceability not ULS. With a kl of 1.0 they would pass.

An approach has been floated;
For ULS, apply a kl of 1.5 (or whatever required) and check capacity against ULS combinations. Check SLS limits using a kl of 1.0 against specified deflection criteria.

My issue is, I cannot find anything in the code that says we can use the above approach. Although, I think the approach is wholly reasonable considering the SLS deflection criteria is suggestive.

Any thoughts / comments would be appreciated.
 
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I've always taken the same Kl factors at ULS & SLS. I believe that is the intent.

Local pressure factors are a function of the building geometry, not a factor of the wind speed. Same effect occurs irrespective of wind pressure/wind speed.

 
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