Wind loads on bldg with stepped roof

[akamike]

I'm determining the wind loads on the walls of a building that steps up twice in elevation. The horizontal dimension of the steps is 20'. Successive heights are 35', 61', 78'. Would you use a mean roof height of 78' to evaluate the entire structure? Or use 35' to evaluate wind loads on the shortest facade, etc.? (I'm only concerned with cladding & components, not MWFRS.)

Secondary question: The building also gets wider as it steps up. So the middle section has 30' of wall peeking out one side and 200' of wall along the top. Would the discontinuity zone width, a, equal 3' at the side wall and 20' along the top wall? Or would the side wall be in a discontinuity zone for the whole width?

 

[WillisV]

You would use the overall building height of 78' to evaluate the leeward negative pressures (qh) at all locations and the actual height (qz) to evaluate the positive windward pressures at each location.