a 1 wind pressure research on low buildings peter j. vickery applied research associates, inc. 8537...
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1
Wind Pressure ResearchWind Pressure Researchon Low Buildingson Low Buildings
Peter J. VickeryApplied Research Associates, Inc.8537 Six Forks Road, Suite 600
Raleigh, NC, 27615
Expanding the Realm of Possibility 2
Wind Tunnel TestsWind Tunnel Tests
Expanding the Realm of Possibility
Pressure TestsPressure Tests
3
Roof Slope
Roof Shape # Stories Basic Terrains Near-by House Spacing Studies (interference Effects)
Trees Analyzed for Code Comparisons
4:12 Hip Gable 1 2 3 Open Sub L L/2 Yes Yes 5:12 Hip Gable 1 2 3 Open Sub L L/2 L/4 L/8 Yes 6:12 Hip Gable 1 2 3 Open Sub L L/2 L/4 L/8 No 7:12 Hip Gable 1 2 3 Open Sub Yes No 9:12 Hip Gable 1 2 3 Open Sub Yes 12:12 Hip Gable 1 2 3 Open Sub Yes Flat 1 2 3 Open Sub Yes
Yes Yes Yes
No Yes No
Expanding the Realm of Possibility
Effect of Roof Slope - GableEffect of Roof Slope - Gable
4
-3.5
-3-3
-3
-2.5
-2.5
-2.5
-2.5
-2
-2
-2
-2
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1-1
-2.5
-3
-3-3
-4.14
Gable4:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-4-3.5 -3
-3
-2.5
-2.5
-2
-2
-2
-2
-2
-1.5
-1.5
-1.5
-1.5
-1.5
-1
-1
-4.23
Gable5:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-2.5
-2
-2
-2
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1
-1
-1
-1
-3.27
Gable6:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-2
-2
-1.5
-1.5
-1.5
-1.5
-1
-1
-3.53
Gable7:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-2.5
-2 -2
-2
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-3.15
Gable9:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-1.5-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-3.32
Gable12:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
Expanding the Realm of Possibility
Effect of Roof Slope - GableEffect of Roof Slope - Gable
5
-2
-2
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-2
-2
-2
-2 -2
-2
-2
-2
-1-1
Hip4:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1.5
-1
-1
-1
-1
Hip5:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-1.5-1.5
-1.5
-1.5
-1.5
-1.5
-1
-1
-1-1
-1
-1
-1
-1
Hip6:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-1.5
-1
-1
-1
-1
-1
-1-1
-1.5 -1.5
Hip7:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-2
-2
-1.5
-1.5
-1
-1
-1
-1
-1
-1
-1.5-1.5
Hip9:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
-2.5
-2.5
-2
-2
-1.5
-1.5
-1.5
-1.5
-1
-1
-1
-1
-1
-1
-1.5
-1.5-2 -2
Hip12:12-Open-2 Story
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
Expanding the Realm of Possibility
4:12 Code Comparisons4:12 Code Comparisons
6
Gable End
Zone 2 GCp Values - Gable Ridge
0
1
2
3
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
ASCE 7-05 Zone 2 GCp
1 Story Open
1 Story Suburban
2 Story Open
2 Story Suburban
3 Story Open
3 Story Suburban
2 Story Suburban A
2 Story Suburban B
Zone 2 GCp Values - Gable End
0
1
2
3
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
ASCE 7-05 Zone 2 GCp
1 Story Open
1 Story Suburban
2 Story Open
2 Story Suburban
3 Story Open
3 Story Suburban
2 Story Suburban A
2 Story Suburban B
Gable Ridge
Expanding the Realm of Possibility
4:12 Code Comparisons4:12 Code Comparisons
7
Gable Ridge Gable Eave
Zone 3 Gable Eave
0
1
2
3
4
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
ASCE 7-05 Zone 3 GCp
1 Story Open
1 Story Suburban
2 Story Open
2 Story Suburban
3 Story Open
3 Story Suburban
2 Story Suburban A
2 Story Suburban B
Zone 3 Gable Ridge
0
1
2
3
4
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
ASCE 7-05 Zone 3 GCp
1 Story Open
1 Story Suburban
2 Story Open
2 Story Suburban
3 Story Open
3 Story Suburban
2 Story Suburban A
2 Story Suburban B
Expanding the Realm of Possibility
7:12 Code Comparisons7:12 Code Comparisons
8
Gable EndGable Ridge
Zone 2b (Gable Ridge, Gable 7:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp -4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Zone 2a (Gable End, Gable 7:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Expanding the Realm of Possibility
7:12 Possible Solution7:12 Possible Solution
9
Gable EndGable Ridge
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Zone 2a (Gable End, Gable 7:12)-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 2b (Gable Ridge, Gable 7:12)-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Expanding the Realm of Possibility
7:12 Code Comparisons7:12 Code Comparisons
10
Gable Ridge Gable Eave
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Zone 3a (Gable Ridge, Gable 7:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 3b (Gable Eave, Gable 7:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)E
xte
rna
l Pre
ss
ure
Co
eff
icie
nt,
GC
p
Expanding the Realm of Possibility
9:12 Code Comparisons9:12 Code Comparisons
11
Gable EndGable Ridge
Zone 2a (Gable End, Gable 9:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)E
xte
rna
l Pre
ss
ure
Co
eff
icie
nt,
GC
p
Zone 2b (Gable Ridge, Gable 9:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp -4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Expanding the Realm of Possibility
9:12 Code Comparisons9:12 Code Comparisons
12
Gable Ridge Gable Eave
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Zone 3b (Gable Eave, Gable 9:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 3a (Gable Ridge, Gable 9:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Expanding the Realm of Possibility
12:12 Code Comparisons12:12 Code Comparisons
13
Gable EndGable Ridge
Zone 2b (Gable Ridge, Gable 12:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 2a (Gable End, Gable 12:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Expanding the Realm of Possibility
12:12 Code Comparisons12:12 Code Comparisons
14
Gable Ridge Gable Eave
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Zone 3b (Gable Eave, Gable 12:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)E
xte
rna
l Pre
ss
ure
Co
eff
icie
nt,
GC
p
Zone 3a (Gable Ridge, Gable 12:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Expanding the Realm of Possibility
Gable Roof Zone 1Gable Roof Zone 1
15
Zone 1 (Gable 7:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 1 (Gable 9:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 1 (Gable 12:12)
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Expanding the Realm of Possibility
7:12 Hip7:12 Hip
16
Zone 3 (Hip 7:12)-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 2a (Hip Edge, Hip 7:12)-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 2b (Eave Edge, Hip 7:12)-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
ASCE 7-05 Gable/Hip Roofs10°<Slope≤30°
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Assumes Designer uses ASCE 7-05 GableRoof Coefficients for 30°< Slope ≤ 45°
Expanding the Realm of Possibility
9:12 Hip9:12 Hip
17
ASCE 7-05 Gable/Hip Roofs10°<Slope≤30°
Zone 2a (Hip Edge, Hip 9:12)-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)E
xte
rna
l Pre
ss
ure
Co
eff
icie
nt,
GC
p
Zone 2b (Eave Edge, Hip 9:12)-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 3 (Hip 9:12)-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Assumes Designer uses ASCE 7-05 GableRoof Coefficients for 30°< Slope ≤ 45°
Expanding the Realm of Possibility
12:12 Hip12:12 Hip
18
ASCE 7-05 Gable/Hip Roofs10°<Slope≤30° -4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
1 Story Suburban
1 Story Open
2 Story Suburban
2 Story Open
3 Story Suburban
3 Story Open
ASCE 7-05
Zone 3 (Hip 12:12)-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ext
ern
al P
ress
ure
Co
effic
ien
t, G
Cp
Zone 2a (Hip Edge, Hip 12:12)
-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Zone 2b (Eave Edge, Hip 12:12)-4.0
-3.0
-2.0
-1.0
0.0
1 10 100 1000
Effective Wind Area (sq. ft)
Ex
tern
al P
res
su
re C
oe
ffic
ien
t, G
Cp
Assumes Designer uses ASCE 7-05 GableRoof Coefficients for 30°< Slope ≤ 45°
Expanding the Realm of Possibility
Interference EffectsInterference Effects
Exposure 3Exposure 4
Exposure 5Exposure 6
Expanding the Realm of Possibility
Hip 5:12 Exposure 6 vs. Sub-UrbanHip 5:12 Exposure 6 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 5:12 Exposure 5 vs. Sub-UrbanHip 5:12 Exposure 5 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 5:12 Exposure 4 vs. Sub-UrbanHip 5:12 Exposure 4 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 5:12 Exposure 3 vs. Sub-UrbanHip 5:12 Exposure 3 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 6:12 Exposure 6 vs. Sub-UrbanHip 6:12 Exposure 6 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 6:12 Exposure 5 vs. Sub-UrbanHip 6:12 Exposure 5 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 6:12 Exposure 4 vs. Sub-UrbanHip 6:12 Exposure 4 vs. Sub-Urban
Expanding the Realm of Possibility
Hip 6:12 Exposure 3 vs. Sub-UrbanHip 6:12 Exposure 3 vs. Sub-Urban
Expanding the Realm of Possibility
Gable 5:12 Exposure 6 vs. SuburbanGable 5:12 Exposure 6 vs. Suburban
Expanding the Realm of Possibility
Gable 5:12 Exposure 5 vs. SuburbanGable 5:12 Exposure 5 vs. Suburban
Expanding the Realm of Possibility
Gable 5:12 Exposure 4 vs. SuburbanGable 5:12 Exposure 4 vs. Suburban
Expanding the Realm of Possibility
Gable 5:12 Exposure 3 vs. SuburbanGable 5:12 Exposure 3 vs. Suburban
Expanding the Realm of Possibility
Gable 6:12 Exposure 6 vs. SuburbanGable 6:12 Exposure 6 vs. Suburban
Expanding the Realm of Possibility
Gable 6:12 Exposure 5 vs. SuburbanGable 6:12 Exposure 5 vs. Suburban
Expanding the Realm of Possibility
Gable 6:12 Exposure 4 vs. SuburbanGable 6:12 Exposure 4 vs. Suburban
Expanding the Realm of Possibility
Gable 6:12 Exposure 3 vs. SuburbanGable 6:12 Exposure 3 vs. Suburban
Expanding the Realm of Possibility
Sub-Urban Exposure-6 Exposure-5
Exposure-4 Exposure-3
Gable 5:12 GCp (Wind Direction 40)Gable 5:12 GCp (Wind Direction 40)
Expanding the Realm of Possibility
Sub-Urban Exposure-6 Exposure-5
Exposure-4 Exposure-3
Gable 6:12 GCp (Wind Direction 40)Gable 6:12 GCp (Wind Direction 40)
Expanding the Realm of Possibility
SummarySummary Papers describing results are still in preparation. Results show for gable roofs ASCE 7 coefficients for
roofs are too low (not new). Use of gable loads for hip roofs with slopes > 30° will
underestimate loads. Simple improvement could be to use the Gable/Hip
10° < θ ≤ 30° for all hip roofs
38
Expanding the Realm of Possibility
SummarySummary Resistance to increase loads in ASCE 7 (even though
data shows code loads are too high) is because of shielding Work by Ho (1993) showed that neighboring
buildings decrease wind loads by ~25% New work shown here (based on the new 5:12 and
6:12 experiments) shows similar reductions EXCEPT near the high section gable ridge areas.
Perhaps could use this finding to force use of Exposure C for all roof C&C loads
39