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I need to design a vaulted roof under wind loads and need to determine the pressure coefficients for zones A, B and C. My problem is with zone A where I need to interpolate values for the case h/d<0.5 (in my case it is 0.3) and f/d=0.25.

As per the code I were to use both positive and negative values of A for h/d>0.5 but since h/d=0.3 for me then I need to interpolate by taking h=0 reference line and the h/d>0.5 line. As you can see in my sketch (last case) there are 2 lines defining zone A and I am not sure which one to use for linear interpolation?

I will appreciate any help, thx in advance.

enter image description here

VCN
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1 Answers1

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THe second note says: for $0,2 \le h/d \le 0,3$ and $h/d \ge 0,5$, two values of $C_{pe,10}$ have to be considered. In another word, only a single $C_{pe,10}$ needs to be considered for other cases. Your case falls into the latter category, so $C_{pe,10} \approx 0,3$.

enter image description here

r13
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  • Thank you for your answer but I am already aware that only one value of Cpe needs to be evaluated with interpolation. I would like to know why did you use the line with positive values (red one in my last sketch) for interpolation? Why we do not follow the blue one? – VCN Apr 15 '22 at 15:13
  • The blue line you showed is for zone A (h/d >= 0.5). See updated graph. It should be self-explanatory. – r13 Apr 15 '22 at 17:36
  • **"The blue line you showed is for zone A (h/d >= 0.5)"** So the red line is also for zone A (h/d>= 0.5); thats why I am wondering why you prefer to interpolate between positive values. I mean which line are you going to use if f/d=0.1 and h/d<0.25? I guess you will respond Cpe=-1.2+[0.16-(-1.2)]*[0.25/0.5]=-0.52 ? – VCN Apr 16 '22 at 06:56
  • The blue line in my graph is for A(h = 0), see legend. The blue line on your third graph was for A(h/d . = 0.5).. Yes, h/d < 0.25 falls in between the red line and the blue line (on my graph), with f/d=0.1, the line goes down and has a negative Ce. I think you got it now, but reluctant to admit. – r13 Apr 16 '22 at 14:19
  • "I am wondering why you prefer to interpolate between positive values." No, it is not a preference, but from the note "For Zone A: • for 0< hid < 0,5, the coefficient Cpe, 10 is obtained by linear interpolation". Therefore the interpolated line of h/d must fall within the lines representing h/d = 0, and h/d > 0.5. Since, for h/d = 0, the entire line is above Ce = 0, as well as the adjacent c/d > 0.5, thus, the interpretation line can only have positive Ce values. – r13 Apr 16 '22 at 16:42