ASCE 7-10 Wind Speed Map - Okaloosa Countygis.okaloosafl.com/gm_docs/ASCE Wind Map by Peter...
Transcript of ASCE 7-10 Wind Speed Map - Okaloosa Countygis.okaloosafl.com/gm_docs/ASCE Wind Map by Peter...
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ASCE 7-10 Wind Speed Map
Peter J. VickeryApplied Research Associates, Inc.8537 Six Forks Road, Suite 600
Raleigh, NC, 27615
Objectives of Presentation
Rationale behind 300, 700 and 1700 return period maps
Basis for new wind speed maps
Basis for re-introduction of Exposure D
Basis for missile impact area
Expanding the Realm of Possibility
Facts About the ASCE 7-05 Wind Speed Map In most of the non-hurricane US mainland, the
mapped values are exactly a 50 year mean recurrence interval (MRI)
Wind speeds in hurricane prone regions are NOT 50 year MRI values. The mapped values vary from ~50 to ~100 years along the hurricane coastline.
Wind speeds along the hurricane coastline have been adjusted upward so that when incorporated with the wind LF, produce a wind load having a consistent hazard level with the interior US (~700 MRI)
Expanding the Realm of Possibility
ASCE 7-10 Wind Maps New Hurricane Simulation Model
Windfield
Filling (weakening after landfall)
Holland B (pressure-wind Relationship)
Tracks and pressures (Landfall location and intensity)
Results in Lower Design Wind Speeds
ASCE 7-10 uses a strength or limit state wind speed map (wind load factor = 1 for strength design, 0.6 for ASD)
Strength map corresponds to 700 year RP
ASCE 7-05 Equivalent Map = V700/√1.6
Category III and IV structures use 1700 year RP winds
Category I structures use 300 year RP winds
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Expanding the Realm of Possibility
0.0
0.5
1.0
1.5
2.0
2.5
1 10 100 1000 10000
Load
Factor [VT/V50]2
Return Period (Years)
WLF*1.143 = 1.828
1.143
50 709 1697
1.00
Hurricane (Miami)
Non‐Hurricane
[VT/V50]2=[0.36+0.1ln(12T)]2
WLF = 1.6
Expanding the Realm of Possibility
0.0
0.5
1.0
1.5
2.0
2.5
1 10 100 1000 10000
Load
Factor [VT/V50]2
Return Period (Years)
WLF*1.143 = 1.828
1.143
50 709 1697
1.00
Hurricane (New York City)
Non‐Hurricane
[VT/V50]2=[0.36+0.1ln(12T)]2
WLF = 1.6
Expanding the Realm of Possibility
Basis of Design Wind Speeds New Hurricane Simulation Model
Improved wind field model
New filling model (weakening after landfall)
New Holland B model (pressure-wind relationship)
New model for tracks and pressures (landfall location and intensity)
Results in lower design wind speeds
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0
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120
140
160
180
10 100 1000 10000
Pea
k G
ust
Win
d S
pee
d (
mp
h)
Return Period (Years)
Hurricanes
Non-Hurricanes
Combined
Expanding the Realm of Possibility
Additional Data in New Model
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Parameter 2000
Model Current Model Increase
Number of full scale wind speed traces (with maximum wind recorded) used to validate windfield model
63 245 390%
Number of dropsonde profiles used to verify marine boundary layer model
0 650
Number of hurricanes used to develop Holland B model 17 35 100% Number of landfall hurricanes 167 189 13% Number of landfall intense hurricanes (defined by pressure) 70 84 20% Number of hurricanes used to develop filling model 38 57 68% Number of years of landfall data used to develop model 96 107 11%
Expanding the Realm of Possibility
Simulation Methodology
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Step 2:
5oSquares
Sample new and Vt
Compute new value of I
Compute Pc, B, RMW
B, RMW from Vickery and Wadhera (2008)
Step 1:
Initialize Storm
Sample B and RMW error terms
Compute I
Step 3:Storm Filling Central pressure filling (Vickery, 2005)
B filling
Site Lat and Long
Distance inland vs. direction
Step 4:
Windfield model (Vickery et al, 2008) turned on
if storm within 250 km of site
V = f {Pc, B, RMW, Vt, r}
1008
997998998991
982972
969973982
981987987988976975966966
941950936924928
966
981
981
985
985
982984
991
991
990
990
988
988
987
1006
998
993
991
987
987
986
983
973
974
946
949
953
94895
496097
0
974
974
945
943
949
951
96196
9976
982
Central Pressure
(6 hour interval)
Expanding the Realm of Possibility
Wind Model Overview
Described in peer reviewed engineering and meteorological literature.
Includes asymmetries caused by variable friction as well as translation speed
Wind speed variation with height model using dropsonde data
Extensively validated over land and water
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Expanding the Realm of Possibility
Track Model Verification Comparison of land fall rates by pressure
Comparisons of modeled and observed translation speeds, heading, occurrence rates and distance of closest approach
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Step 2:
5oSquares
Sample new and Vt
Compute new value of I
Compute Pc, B, RMW
B, RMW from Vickery and Wadhera (2008)
Step 1:
Initialize Storm
Sample B and RMW error terms
Compute I
Step 3:Storm Filling Central pressure filling (Vickery, 2005)
B filling
Site Lat and Long
Distance inland vs. direction
Step 4:
Windfield model (Vickery et al, 2008) turned on
if storm within 250 km of site
V = f {Pc, B, RMW, Vt, r}
1008
99799899899
198
297
2969
97398298
198798798897697596
696694195
0936924928
966
981
981
985
985
982984
991
991
990
990
988
988
987
1006
998
993
991
987
987
986
983
973
974
946
949
953
94895
496097
0
974
974
945
943
949
951
96196
9976
982
Central Pressure
(6 hour interval)
TX
890
910
930
950
970
990
1 10 100 1000Return Period (years)
Cen
tral
Pre
ssu
re
(mb
)
Expanding the Realm of Possibility
Charley Validation Summary
ASOS Description
Obs ModelKFMY Fort Myers International Airport 85 81KMCO Orlando International Airport 107 109KSFB Orlando Sanford International Airport 94 92KORL Orlando Executive International Airport 87 98KMIA Miami International Airport 41 34KMLB Melbourne Regional Airport 49 53KPBI Palm Beach International Airport 41 37KRSW Ft Myers Regional Airport 81 70FCMP T0 FCMP Tower 0 54 59FCMP T1 FCMP Tower 1 76 82FCMP T2 FCMP Tower 2 49 46FCMP T3 FCMP Tower 3 39 43SAUF1 St Augustine C-MAN Platform 71 65
Peak Gust Speed(mph)
y = 0.98xR² = 0.92
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120
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Pe
ak
Gu
st
Win
d S
pe
ed
(m
ph
) -
Mo
de
led
Peak Gust Wind Speed (mph) - Observations
Right
Left
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8/13/04 18:00 8/13/04 19:00 8/13/04 20:00 8/13/04 21:00 8/13/04 22:00
Pea
k G
ust
Win
d S
pe
ed
(mp
h)
Time (UTC)
Hurricane Charley - KPGD
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Me
an
Win
d S
pee
d (m
ph
)
Time (UTC)
Hurricane Charley - KPGD
Expanding the Realm of Possibility
Why Lower Wind Speeds?
New model produces more intense landfalling hurricanes than the old model but results in lower wind speeds.
Lower winds largely associated with a new statistical model for the Holland B parameter, which controls the wind-pressure relationship.
Paper describing the statistical model for B was published in the Journal of Applied Meteorology in December 2008.
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Expanding the Realm of Possibility
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Distance from Storm Center (r/RMW)
Gra
die
nt
Ba
lan
ce
Win
d S
pe
ed
(ms
-1)
B = 0.75B = 1B = 1.3B = 1.5
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Distance from Storm Center (r/RMW)
Pre
ss
ure
e (
hP
a)
B = 0.75B = 1B = 1.3B = 1.5
Holland B defines the width and peakedness of the wind field
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B
c r
RMWpprp
exp)(
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])(exp[)(
2/1
22 frfrr
RMWpB
r
RMWV
B
BG
epB
VG
max
Expanding the Realm of Possibility
Holland B Pressure Fits
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050100150
940
960
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1000
1020Andrew -1992/08/23-0542,B=1.6,p=75mb,RMW=11km
Radius(km)
Pre
ssu
re(h
Pa)
050100150
940
960
980
1000
1020Floyd-1999/09/15-0518,B=1.15,p=80mb,RMW=66km
Radius(km)
Pre
ssu
re(h
Pa)
0 50 100 150
940
960
980
1000
1020Floyd-1999/09/15-0525,B=1.1,p=81mb,RMW=65km
Radius(km)
Pre
ssu
re(h
Pa)
0 50 100 150
940
960
980
1000
1020Andrew -1992/08/23-0550,B=1.7,p=79mb,RMW=13km
Radius(km)
Pre
ssu
re(h
Pa)
050100150
940
960
980
1000
1020Luis-1995/09/04-1700,B=1.4,p=71mb,RMW=42km
Radius(km)
Pre
ssu
re(h
Pa)
0 50 100 150
940
960
980
1000
1020Luis-1995/09/04-1704,B=1.5,p=71mb,RMW=38.5km
Radius(km)
Pre
ssu
re(h
Pa)
Expanding the Realm of Possibility
Effect of Holland B on Predicted Wind Speeds
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Peak Gust W
ind Speed (mph)
Return Period (years)
Wilmington, NC
B from Vickery, et al. (2000)
B from Vickery and Wadhera (2008)
Expanding the Realm of Possibility
Wind Speed Comparisons
90(40)
90(40)
100(45)110(49)
130(58) 130(58)
120(54)
110(49)
110(49)
90(40)
100(45)
140(63)
110(49)
120(54)
120(54)
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ASCE 7-98 through 7-05ASCE 7-10 Equivalent(V700/√1.6)
Expanding the Realm of Possibility
700 Year Return Period Winds
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Location Vmph (m/s)Hawaii 129 (58)Guam 196 (88)Virgin Islands 167 (75)American Samoa 158 (71)
Puerto Rico
114(51)
108(48)
114(51)
114(51)150(67)
140(63)120(54)
130(58)
170(76)160(72)
180(80)
180(80)
170(76)160(72)
150(67)
140(63)
140(63)
150(67)
140(63)
130(58)
120(54)
114(51)
110(49)
150(67)
120(54)130(58)140(63)
158(71)
158(71)
150(67)140(63)
130(58)
120(54)
110(49)
150(67) 160(72)
170(76)
Expanding the Realm of Possibility
Wind speeds at selected locationsLocation 6.1/700V
ASCE 7-05 Exposure C
Exposure C Exposure D Bar Harbor, Maine 97 95 103 Boston, MA 106 103 112 Hyannis, MA 117 112 122 New Port, RI 117 109 119 Southampton, NY 120 110 119 Atlantic City, NJ 114 102 111 Wrightsville Beach, NC 132 119 129 Folly Beach, SC 131 115 125 Miami Beach 145 136 148 Clearwater, FL 128 115 125 Panama City, FL 129 107 116 Biloxi, MS 138 129 140 Galveston, TX 131 119 129 Port Aransas, TX 134 117 127 Hawaii 105 103 112 Guam 170 155 168
Expanding the Realm of Possibility
020406080
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Pea
k G
ust
Win
d S
pee
d (
mp
h)
Return Period (years)
Texas
Car
la
Au
dre
y
Cel
ia
1932
1900
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120
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Pea
k G
ust
Win
d S
pee
d (
mp
h)
Return Period (years)
Louisiana
Cam
ille
Bet
sy
Kat
rin
a
Au
dre
yC
arm
en
An
dre
w
Rit
a
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Pea
k G
ust
Win
d S
pee
d (m
ph
)
Return Period (years)
MS/AL
Cam
ille
Kat
rin
a19
26
Fre
der
icE
len
a
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Pea
k G
ust
Win
d S
pee
d (m
ph
)
Return Period (years)
Florida
Ch
arle
y
Lab
or
Day
An
dre
w
1926
Do
nn
a
Simulated vs. Historical Maximum Wind Speeds
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Expanding the Realm of Possibility
Peak Gust Wind Speeds Anywhere in US vs. Return Period
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250
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Win
d S
pe
ed
(m
ph
)
Return Period (years)
ARA ModeledProbabilisticPowell & Reinhold (2007)Powell (2007)Powell & Aberson (2001)Dunion et al, (2003)HWindFIU FCHLPMHouston & Powell (2003)Goldman & Ushijima (1974)
Haz
el
Car
la
Bet
sy (L
A)
Ch
arle
y
Labo
r Day
Cam
ille
An
dre
w
Expanding the Realm of Possibility
Reintroduction of Exposure D in Hurricane- Prone Regions Research showed that the roughness of ocean does
not continue to increase with increasing wind speed” and Exposure D is valid
Expanding the Realm of Possibility
Exposure D
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0.0001
0.001
0.01
0.1
1
10
100
0 10 20 30 40 50
Hei
gh
t (m
)
WInd Speed (m/sec)
Analysis of dropsonde data indicate that at high wind speedsthe ocean roughness does not continue to increase as previously thought.
Reduced drag possibly due to surface bubbles and/or sea spray.
Limits the aerodynamic roughness length to a value comparable to that used to define Exposure D.
Expanding the Realm of Possibility
Roughness Length vs. Wind Speed
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0.0001
0.001
0.01
0.1
1
0 10 20 30 40 50 60 70
Aerodyn
amic Surface Roughness (m
)
Hourly Mean Wind Speed Over Water (m/sec)
Exposure D
Exposure B
Old Model (ASCE 7‐05)
New Model (Large Hurricanes)
New Model (Small Hurricanes)
Estimates from Dropsondes
CAT 5CAT 4CAT 3CAT 2
Exposure C
CAT 1
Expanding the Realm of Possibility
Windborne Debris Region
ASCE 7-05 Standard
V > 120 or 110 within one mile of coast
Exact Mapping (new 700 year map)
120√1.6=152~150
110 √1.6=139~140
Implemented
V > 140 or 130 within one mile of coast
Results in less area within WBD Region than in the ASCE 7-05
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Expanding the Realm of Possibility
ASCE 7-10 Windborne Debris Region
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Expanding the Realm of Possibility
Wind Map Summary New data and data analysis indicate that the ASCE 7-05
hurricane wind speeds were generally conservative
Introduction of ultimate wind speed maps
LRFD Wind Load Factor = 1.0
ASD Wind Load Factor = 0.6
Specific maps for each building category
Exposure D for hurricane coastline
New windborne debris region results in less area subject to windborne debris design criteria