Wind force coeff Cf when h/d > 25 for cylindrical structures?
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Question

Wind force coeff Cf when h/d > 25 for cylindrical structures?

IJR (Structural)

(OP)

21 Apr 07 02:18

Pals

I have a copy of ASCE 7-88

for vertical cylindrical shapes(chimneys tanks and similar) wind force coefficients depend on ration h/d, d.root(q) and surface roughness. Values given in ASCE 7-88 table 12 stop when h/d = 25.

ASCE puts a note that you can interpolate for values of h/d not shown in the table.

This statement says nothing about the limits of h/d.

What happens when h/d > 25 (The cylinder is very slender but so many cylinders we know have h/d > 25)

respects

IJR

civilperson (Structural) · Answer 1 · 2007-04-21 12:16:59

The h/d>25 is the same value as h/d=25. End & edge effects are minimal for long pipes and similar shapes.

IJR (Structural) · Answer 2 · 2007-04-24 06:15:57

Thank you Civilperson

Do you know anywhere in the code where I can find a reference to your comment?

dik (Structural) · Answer 3 · 2007-04-24 09:34:54

The only reference I have is for h/d = 25... the general data comes from Report Nr 160 from Swiss Assoc of Eng and Arch (1956). The data is in Supplement 3 to the NBC of Canada 1960. It also notes smoothe and rough surfaces. For taller structures, I'd use the increased forces for height. The loading information has the pressure located at increments of 15degrees. I don't know what ASCE-7 has.

Dik

LHiggins (Structural) · Answer 4 · 2007-04-24 12:14:26

ASCE7-05 has the same table and has not referenced anything else. It has to be assumed that the values in the table are for h/D less than or equal to 1 and greater than or equal to 25.

Larry

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Wind force coeff Cf when h/d > 25 for cylindrical structures?
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