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)


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

4


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


0.0

0.5

1.0

1.5

2.0

2.5

1 10 100 1000 10000

Load

Factor [VT/V50]2


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


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

20

40

60

80

100

120

140

160

180

10 100 1000 10000

Pea

k G

ust

Win

d S

pee

d (

mp

h)


Hurricanes

Non-Hurricanes

Combined


Additional Data in New Model

8

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%


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)


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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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

)


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

0

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40

60

80

100

120

0 20 40 60 80 100 120

Pe

ak

Gu

st

Win

d S

pe

ed

(m

ph

) -

Mo

de

led

Peak Gust Wind Speed (mph) - Observations

Right

Left

0

30

60

90

120

150

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

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Win

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(mp

h)

Time (UTC)

Hurricane Charley - KPGD

0

20

40

60

80

100

120

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

Me

an

Win

d S

pee

d (m

ph

)

Time (UTC)

Hurricane Charley - KPGD


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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0 1 2 3 4 5 6 7 8 9 10

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

930

940

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990

1000

1010

1020

0 1 2 3 4 5 6 7 8 9 10

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)(

24

])(exp[)(

2/1

22 frfrr

RMWpB

r

RMWV

B

BG

epB

VG

max


Holland B Pressure Fits

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050100150

940

960

980

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)


Effect of Holland B on Predicted Wind Speeds

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0

50

100

150

200

1 10 100 1000

Peak Gust W

ind Speed (mph)

Return Period (years)

Wilmington, NC

B from Vickery, et al. (2000)

B from Vickery and Wadhera (2008)


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)


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)


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


020406080

100120140160180200220

1 10 100 1000

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Texas

Car

la

Au

dre

y

Cel

ia

1932

1900

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Louisiana

Cam

ille

Bet

sy

Kat

rin

a

Au

dre

yC

arm

en

An

dre

w

Rit

a

020406080

100120140160180200220

1 10 100 1000

Pea

k G

ust

Win

d S

pee

d (m

ph

)


MS/AL

Cam

ille

Kat

rin

a19

26

Fre

der

icE

len

a

020406080

100120140160180200220

1 10 100 1000

Pea

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d (m

ph

)


Florida

Ch

arle

y

Lab

or

Day

An

dre

w

1926

Do

nn

a

Simulated vs. Historical Maximum Wind Speeds

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Peak Gust Wind Speeds Anywhere in US vs. Return Period

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1 10 100 1000

Win

d S

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(m

ph

)


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


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


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.


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


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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ASCE 7-10 Windborne Debris Region

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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

asce 7-10 wind speed map - okaloosa countygis.okaloosafl.com/gm_docs/asce wind map by peter...

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