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# ASCE-7 '02 External Pressure Coefficient2

## ASCE-7 '02 External Pressure Coefficient

(OP)
Im making a program for wind calculation..
In Figure 6-6(con't), in getting the value of Roof Pressure Coefficient Cp, where do you get the value of Cp when Roof Angle is than 10 and h/L is between 0.5 and 1.0?
Since the table shows only values of h/L <=0.5 and >=1.0
Help much appreciated!

### RE: ASCE-7 '02 External Pressure Coefficient

You would use a linear interpolation between the values provided for less than or equal to h/L of 0.5 and greater than or equal to h/L of 1.0.  For instance if you have an h/L of 0.75 then the Cp for distances from 0 to h/2 from the edge would be midway between -0.9 and -1.3 (-1.1).

### RE: ASCE-7 '02 External Pressure Coefficient

I agree with WillisV, to a point.

You would have to do four linear interpolations,

1)  for dist from windward edge 0 to h/2   Cp = -1.1 or -.18
2)  for dist from windward edge h/2 to h   Cp = -0.8 or -.18
3)  for dist from windward edge h to 2h    Cp = -0.6 or -.18
4)  for dist from windward edte > 2h       Cp = -0.4 or -.18

ALso, note that the first one can have a reduction factor applied to the interpolation number for the high side (h/L = 1.0; Cp = -1.3) based on effective area; this reduction does not apply to the interpolation number on the low side (h/L = 0.5; Cp = -0.9)

regards,

chichuck

### RE: ASCE-7 '02 External Pressure Coefficient

(OP)
Thanks!
thats what i did for now.. Interpolate for the upper, interpolate for the lower.. then interpolate again..

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