C&C External Pressure Coefficient in ASCE
C&C External Pressure Coefficient in ASCE
(OP)
Welp I'm a moron. Made a wind spreadsheet a while ago and failed to realize that the GCp is on a logarithmic scale. Makes sense, diminished returns bla bla bla...
Anyways, I can't find any equation for the Gcp other than interpolating the graph. Is there at least any data points other than 10sf and 500sf (the end points)?
Like for Figure 30.4-1, For Zone for 10sf = +1.0 and 500sf = +0.7. 20sf looks like 0.95. But could be 0.96 or 0.94. Is there anywhere that tells exactly what these points are. Looked but couldn't find.
Thanks.
Anyways, I can't find any equation for the Gcp other than interpolating the graph. Is there at least any data points other than 10sf and 500sf (the end points)?
Like for Figure 30.4-1, For Zone for 10sf = +1.0 and 500sf = +0.7. 20sf looks like 0.95. But could be 0.96 or 0.94. Is there anywhere that tells exactly what these points are. Looked but couldn't find.
Thanks.






RE: C&C External Pressure Coefficient in ASCE
G can be determined by Eq. 26.9-6 but I can only find a few tabular references for Cp that include Components and Cladding (C&C). There are considerably more tables of Cp for the Main Windforce Resisting System (MWFRS) but it's unclear to me if they can also be applied to C&C. In any case the code explicitly states that when GCp is listed together they should not be separated lest you incur the wrath of those who don't want their system figured out, apparently. I think the bottom line is just to take the values they give you and reverse engineer your spreadsheet to match them. Sorry.
RE: C&C External Pressure Coefficient in ASCE
RE: C&C External Pressure Coefficient in ASCE
It is cumbersome to program with all the cases, but seems to work well.
RE: C&C External Pressure Coefficient in ASCE
RE: C&C External Pressure Coefficient in ASCE
Positive Zones 4 and 5
GCp = 1.0 for A = 10 sq ft
GCp = 1.1766-0.1766logA for 10 sq ft < A <= 500 sq ft
GCp = 0.7 for A > 500 sq ft
Negative Zone 4
GCp = -1.1 for A = 10 sq ft
GCp = -1.2766+0.1766logA for 10 < A <= 500 sq ft
GCp = -0.8 for A > 500 sq ft
Negative Zone 5
GCp = -1.4 for A = 10 sq ft
GCp = -1.7532 + 0.3532logA for 10 < A <= 500 sq ft
GCP = -0.8 for A > 500 sq ft
RE: C&C External Pressure Coefficient in ASCE
RE: C&C External Pressure Coefficient in ASCE
RE: C&C External Pressure Coefficient in ASCE
Jim H
RE: C&C External Pressure Coefficient in ASCE
=GCpAmin+(LN(MIN(MAX(Amin,B5),Amax))-LN(Amin))*(GCpAmax-GCpAmin)/(LN(Amax)-LN(Amin))
Where
Area is the cell with the area in question
Amin is the cell or value with the smaller limit (eg 10ft2)
Amax is the cell or value with the larger limit (eg 500ft2)
GCpAmin is the value with cell of the GCp corresponding to the smallest area
GCpAmax is the value or cell with the GCp corresponding to the largest area
RE: C&C External Pressure Coefficient in ASCE
I doubled checked the numbers after inputting, even though I reaaalllly didnt want to lol. So they're
accurate per the book.
Gable roof < 10 deg
Positive with and without overhang: Zones 1, 2, and 3
0.4 - 0.1*LOG(A)
Negative w/ out overhang: Zone 1
-1.1 +0.1*LOG(A)
Negative w/ out overhang: Zone 2
-2.5+0.7*LOG(A)
Negative w/ out overhang: Zone 3
-4.5+1.7*LOG(A)
Negative with overhang: Zones 1 and 2
-1.8 + 0.1*LOG(A) for 10 to 100
-3.0307 + 0.7153*LOG(A) for 100 to 500
Negative with overhang: Zone 3
-4.8 + 2.0*LOG(A)
10 deg < Gable roof <= 30 deg
Positive with and without overhang: Zones 1, 2, and 3
0.7 - 0.2*LOG(A)
Negative with and without overhang: Zone 1
-1.0 + 0.1*LOG(A)
Positive without overhang: Zones 2, and 3
-2.8 + 0.7*LOG(A)
Negative with overhang: Zone 2
-2.2
Negative with overhang: Zone 3
-4.9 + 1.2*LOG(A)
30 deg < Gable roof <= 45 deg
Positive with and without overhang: Zones 1, 2, and 3
1.0 - 0.1*LOG(A)
Negative with and without overhang: Zone 1
-1.2 + 0.2*LOG(A)
Negative without overhang: Zones 2 and 3
-1.4 + 0.2*LOG(A)
Negative with overhang: Zones 2 and 3
-2.2 + 0.2*LOG(A)
10 deg < Multispan gabled roofs <= 30 deg
Positive: Zones 1, 2, and 3
0.8 - 0.2*LOG(A)
Negative: Zone 1
-1.8 + 0.2*LOG(A)
Negative: Zone 2
-2.7 + 0.5*LOG(A)
Negative: Zone 3
-3.7 + 1.0*LOG(A)
30 deg < Multispan gabled roofs <= 45 deg
Positive: Zones 1, 2, and 3
1.2 - 0.2*LOG(A)
Negative: Zone 1
-2.9 + 0.9*LOG(A)
Negative: Zone 2
-3.3 + 0.8*LOG(A)
Negative: Zone 3
-3.5 + 0.9*LOG(A)
3 deg < Monoslope roofs <= 10 deg
Positive: All Zones
0.4 - 0.1*LOG(A)
Negative: Zone 2
-1.4 + 0.1*LOG(A)
Negative: Zone 2'
-1.7 + 0.1*LOG(A)
Negative: Zone 3
-2.4 + 0.6*LOG(A)
Negative: Zone 3'
-3.6 + 1.0*LOG(A)
10 deg < Monoslope roofs <= 30 deg
Positive: All Zones
0.5 - 0.1*LOG(A)
Negative: Zone 1
-1.5 + 0.2*LOG(A)
Negative: Zone 2
-2.0 + 0.4*LOG(A)
Negative: Zone 3
-3.8 + 0.9*LOG(A)
Sawtooth roofs >= 10 deg
Positive: Zone 1
0.8766 - 0.1766*LOG(A)
Positive: Zone 2
1.4 - 0.3*LOG(A)
Positive: Zone 3
0.9 - 0.1*LOG(A)
Negative: Zone 1
-2.8474 + 0.6474*LOG(A)
Negative: Zone 2
-4.1418 + 0.9418*LOG(A)
Negative: Zone 3 (SPAN A)
-4.5 + 0.4*LOG(A) for 10 to 100
-8.2782 + 2.2891*LOG(A) for 100 to 500
Negative: Zone 3 (SPANS B, C, and D)
-4.6030 + 1.0015*LOG(A)
Buildings with H > 60ft and Roofs <= 10 deg
Negative: Zone 1
-1.6943 + 0.2943*LOG(A)
Negative: Zone 2
-2.7120 + 0.4120*LOG(A)
Negative: Zone 3
-3.7297 + 0.5297*LOG(A)
Walls All Theta
Positive: Zones 4 and 5
1.1792 - 0.2146*LOG(A)
Negative: Zone 4
-1.0861 + 0.1431*LOG(A)
Negative: Zone 5
-2.5445 + 0.5723*LOG(A)