Wind Load

[MOOK]

In ASCE page 74 (Figure 6-21)

In order to determine the shape (force) coefficient Cf, you need to get h/D from the table.

My question is regarding the definition of h.

Case (I)

If we have tank with height "L = 10ft" on the ground, so the term "h" which will be used in the table

h = 10 ft.

No problem in this case.

Case (II)

If we have tank with height "L=10ft" on a building with height "H= 20ft". There are two opinions:

1- The the term "h" which will be used in the table = H + (L/2) = 25ft. Actuall I found this answer in few references. I really do not understand how did they came up with assumption.

2- ASCE define "h" as height of the structure in feet (look down in the notation) and according to this we should use h = 10 ft.

I have been working for long time with non building structures and I always use h as the height of the structure and I even asked all of my co-workers and all of them use it the same way as me.

Could you please guys give me your feedback.

Thanks

 

[McEngr]

In ASCE page 74 (Figure 6-21)In order to determine the shape (force) coefficient Cf, you need to get h/D from the table.

My question is regarding the definition of h.

Case (I)

If we have tank with height "L = 10ft" on the ground, so the term "h" which will be used in the table

h = 10 ft.

No problem in this case.

Case (II)

If we have tank with height "L=10ft" on a building with height "H= 20ft". There are two opinions:

1- The the term "h" which will be used in the table = H + (L/2) = 25ft. Actuall I found this answer in few references. I really do not understand how did they came up with assumption.

2- ASCE define "h" as height of the structure in feet (look down in the notation) and according to this we should use h = 10 ft.

I have been working for long time with non building structures and I always use h as the height of the structure and I even asked all of my co-workers and all of them use it the same way as me.

Could you please guys give me your feedback.

Thanks

I don't have my ASCE in front of me, but could you explain what Cf is used for? Typically, Kz is used for height. I can do some reading this afternoon and get back with you. However, I will warn you that h/d is typically used for subcritical flow in regards to how the wind passes through an object. h/d is typically an aspect ratio for how the wind approaches an object. Like I said, I'll read more into your case later or on Monday morning.

McEngr

 

[MOOK]

This is a shape factor used for equipments with different shapes, circular, hexagonal, or octagonal. People who work in Non building structures like me use it al ot in wind load calculations.

I used to use it as I explained in my previous message but I found couple of references use it in different way.

Thanks for your care McEngr

 

[McEngr]

MOOK,

Equation 6-28 uses qz, which is dependent on kz, to determine the height of the structure. h/d is only the height and width of the area being considered. I hope that helps.

McEngr

 

[McEngr]

MOOK,Equation 6-28 uses qz, which is dependent on kz, to determine the height of the structure. h/d is only the height and width of the area being considered. I hope that helps.

McEngr

I will politely disagree with ARLORD on this one. Mook, could you please only put your post in a single thread so that we can respond on the same thread?

Thanks.

McEngr

 

[MOOK]

I will politely disagree with ARLORD on this one. Mook, could you please only put your post in a single thread so that we can respond on the same thread?
Thanks.

McEngr

I am not sure what do u mean exactly by single thread.

Actually, I have the book

Structural Load determination under 2006 IBC and ASCE/SEI 7-05 by David Fanella

He get Cf as H+(L/2) and I really do not understand why.

I remember I saw the same thing in another reference but I do not remember it at the moment.