Rule of Thumb Wind Loading 4

[hemis]

I need some rule-of-thumb per-square-metre wind-loads. I have been using 1kN/m2 for some time but I have never checked its "accuracy". May anyone help me please?

 

[MiketheEngineer]

In the US - 15 to 20 psf depending on locations, Exposure Group, height, etc seems about right

 

[lkjh345]

I'm also in the US:

I use 20 psf for main force resisting systems and 25 to 35 psf for components and cladding, depending on the componets location in the building.

 

[shobroco]

On an east or north-east shore of a Great Lake .6kPa is about max. specified by the Cdn Nat. Bldg. Code for any location, so 1 kPa for rule of thumb is pretty conservative for a factored load in any inland location.

 

[hokie66]

This should be dictated by your code and not depend on any rule of thumb. Wind loading varies tremendously with location, especially in areas subject to hurricanes (tropical cyclones). Other factors are height above ground, topography, shielding from other structures, structure shape, the list goes on. As others have indicated, the loading you should use varies also depending on whether you are considering the whole structure or a component thereof. In Australia, wind loading on a given surface can vary from 0.5 kPa (10 psf) to 3.0 kPa (60 psf) or higher.

 

[engstructural]

Im in the UK. I use 1.1kN/m2 for small single elements in domestic construction and find it the be conservative. For anything more significant i would carry out a wind calc.

 

[hemis]

Many thanks for the advice. It seems that my rule-of-thumb is conservative. I have checked my designs using analysis software (and none have ever given a load exceeding 1kN/m2) but, as one of your replies stated, wind is complex and I tend not to trust complicated design procedures such as wind codes which assume topography features, etc. Every site is different and I doubt any site could be modelled accurately. If the rule-of-thumb gives a safe-load, then I am happier using that.

Cheers.

 

[patswfc]

A value of 1kN/m2 is a good value to use as a rule of thumb for concept design.

 

[youngstructural]

Hemis: Rules of thumb are a good one for if you wanted to INCREASE your wind loads, but this is no substitute for mastering the clauses of you code and calculating the code prescribed load in each case.

Regards,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[mfrad]

my rule of thumb:
wind pressure p in psf, wind speed v in mph
p = (v/20)^2

 

[geoffdale]

Canadian codes call for a gust factor of 2.0. So, 0.6 kpa X2= more than your "conservative" factor.

 

[youngstructural]

You probably all know this, however I think it bears mentioning:

You can't compare one to another like this... The Canadian code may require a gust factor, however the wind sample period, or perhaps the percentage value (95th, 5th, etc) could be different.

Good example: Wind loads looked really high to me when I first arrived in New Zealand, until I realised that they aren't factored and have no gust factor.

You need to be especially clear about where you practice when it comes to force of nature loading.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[csd72]

Your wind speed varies with height, it is not that hard to use bs6399, it is considerably easier than ASCE7 and AS1170! Dont be so lazy.

Once you get used to the code it takes 5 minutes.

 

[asixth]

hemis,

Like others have posted, you will need to calculate the wind loads more accuratley from the code and it will depend on a number of variables such as elevation, topology, shielding etc.

I am in Australia and my rules of thumb are

Region A - 1kPa (Melbourne/Sydney)
Region B - 2kPa (Brisbane)
Region C - 3kPa (Northern Australia)
Region D - 4kPa (Port Headland - Mining Area/monsoonal)

Most of my work is in Brisbane and the numbers crunch out to 1.34kPa.