Wind loading to British Standards

[MikePP]

Is anyone out there familiar with wind design to British Standards? I have a cylindrical tank and I want to calculate the overall wind load. The old code (CP3:Ch V) used an overall force coefficient, however the new code (BS 6399 pt 2) does not appear to have this and it is necessary, therefore, to calculate the loading on zones around the tank shell, resolve these in the direction of the wind and add them to give the overall load.
The problem is the CP3 method gives me a result about 50% higher than the BS 6399 method. My questions are:-
Is the method in BS 6399 appropriate for calculating the overall wind load?
Is the CP3 method over-conservative?
Has anybody else experienced the same problem or have I made a mistake somewhere?

Thanks

 

[VoyageofDiscovery]

Hi MikePP,

I am not familiar with the standards you mention. However, BS5400 has formulae, a map of the isles with mean hourly wind speeds, drag coefficients for shape and a table for heights for applied wind load, that will allow you to calculate a wind profile on the structure.

HTH

VOD

 

[VoyageofDiscovery]

I checked the web

try

http://www.anemos.co.uk/S-factors.htm

They have a nice calculator to calculate a factor called Sb

Regards

VOD

 

[MikePP]

Thanks VOD, I checked out BS5400 and it uses the same factors etc as the old British standard. Both of these codes date from the 1970's so I suspect they are on the conservative side. Sb is a 'terrain factor' related to building height and distance from the coast.

MikePP

 

[pba]

I work in the UK and can confirm that most engineers I know are not comfortable with BS6399-2.

Generally it seems to give marginally higher values than CP3 - This is disputed by the authors.

Your approach of calculating a vector sum is the same approach that I have used in the past, but I cannot confirm if it is the CORRECT approach.

I degree of conservatism is probably called for!