Wind Load on a Conical Roof

[KJJ]

I am trying to ascertain the wind load on the roof of a cylindrical projection of a house. The roof is conical with a 4m diameter base and a perpendicular height of approximately 3.8m (the roof is approximately 10m above ground level). BS 6399 Part 2 doesn't offer much help for structures of this size and shape so I was trying to work it out directly using the drag coefficient, projected area and the wind velocity for the area. Can anybobody offer advice on the drag coefficient or even an alternative to my idea?

Many thanks

KJJ

 

[whyun]

UBC97 and CBC98 suggests using 2/3 of the wind pressure on flat elements when you have a cylindrical elements. Conical shape is essentially a cylindrical element with varying diameter thus should be acceptable to apply a 2/3 of the normal pressure.