ASCE 7-10 Figure 29.5-1 h/D clarification

[FreeCrowbars]

I work in telecom and oftentimes we put new structures on existing rooftops. We use Figure 29.5-1 (for "Chimneys, tanks, rooftop equipment, & similar structures over 60') a LOT as it's the best description of the kind of work we do much of the time. The question is what do "h" and "D" really represent in this figure?

I want to put this in terms of "building" and "thing on top of building"
I have heard arguments that "h" is the height of the "building" and other arguments that "h" is the height of the "thing on top of building".
Similarly I've heard that "D" represents the height of the "thing on top of building" and other arguments that "D" is the width of "thing on building".

What are the actual explanations for "h" and "D" for this figure (fig. 29.5-1)?

To make this really simple I've uploaded a simple sketch of a "building" with a "thing" on it. Which value is "h" and which value is "D" with respects to figure 29.5-1?

 

[GC_Hopi]

I would refer to the notes below Figure 29.5-1 and Chapter 26 for definitions. h = mean roof height of a building or height of other structure. D = diameter of circular cross-section... at elevation under consideration. And this Chapter 29.5 applies to structures with h> 60 ft.

From your drawing, you can simplistically/conservatively use h = 4 and D = the least horizontal dimension which would be the lesser of 1 or the in/out of the page dimension of the thing on top of building.

 

[FreeCrowbars]

So least horizontal means "the smallest horizontal dimension"? It doesn't mean "most vertical" dimension? Was this code intentionally written to be as ambiguous as possible?

That said I like your answers. Unless someone else can give a better argument. Thank you.