CSP ARA0157-1

Assessment of Wind Borne Assessment of Wind Borne Debris Criteria for the Debris Criteria for the

Florida PanhandleFlorida PanhandleFebruary 2006

ARA Progress Report

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Scientific Approach--Use Engineering Models Scientific Approach--Use Engineering Models to Quantify Risks, Costs and Benefitsto Quantify Risks, Costs and Benefits

Objective--Perform a engineering-based risk assessment of the hurricane wind borne protection options for the Florida Panhandle.

Approach1. Use ARA’s end to end hurricane and building performance models,

updated with recent data.2. Perform simulations of hurricanes striking the Panhandle, using

updated ASCE-7 hurricane models.3. Use detailed models of 8 residential buildings located at many sites in

the Panhandle4. Assess building damage and loss with and without opening protection

for wind-borne debris5. Aggregate output metrics for direct comparisons of benefits and costs

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Overview of ApproachOverview of Approach

HurricaneHazard

Simulations

SelectLocations

and Buildings

Building Models· WBD Protection

· No WBD Protection

Physical Damage· WBD Protection

· No WBD Protection

Losses· WBD Protection

· No WBD Protection

Model Output Metric· Risks

· Benefits

· Costs

· By Location & Building

Benefits· Avoided Losses

- Building- Contents- Loss of Use-

Costs· FBC Baseline•Additional Costs of

WBD Protection

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Project TasksProject Tasks1. Wind Tunnel Tests. Perform wind tunnel tests for

houses located in treed environments characteristic of the Florida Panhandle. Develop velocity profiles, turbulence intensity and pressure load models for houses in treed environments.

2. Model Representative Houses. Select representative Panhandle houses and develop computer models for analysis of wind borne debris protection effects.

3. Update/Validate Wind Borne Debris Model. Update ARA’s wind borne debris model to reflect new load models and impact resistance data. Perform validation comparisons on window/building performance with available field data on recent Florida Hurricanes.

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Project Tasks (cont’d)Project Tasks (cont’d)

4. Simulate House Performance. Perform hurricane simulations of the representative houses located at various positions in the Panhandle. Evaluate building damage and loss with and without windborne debris protection.

5. Quantify Risks, Benefits, and Costs of Wind Borne Debris Protection. For each house in each Panhandle location, develop the detailed loss reduction data, costs, and risks. Summarize the results and present findings.

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Task 1. Wind Tunnel TestsTask 1. Wind Tunnel Tests

1. Wind tunnel tests have been completed.

2. Data is being analyzed for modeling the mean wind speeds, gusts, and pressures on houses within treed environments.

3. The wind tunnel tests simulated medium and light density forests surrounding houses in subdivisions.

4. The trees simulate 50 and 75 foot tree heights.

5. The velocity profiles compare very well with published profiles from full scale measurements in forests.

6. The results show a significant reduction in windspeeds beneath the trees. The final impact won’t be known until we begin simulating effects on houses.

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Looking Down the Wind Tunnel Looking Down the Wind Tunnel from the Turntablefrom the Turntable

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Wind Fetch Leading to TreesWind Fetch Leading to Trees

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Model House and Surrounding Model House and Surrounding Houses in Treed SubdivisionHouses in Treed Subdivision

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House with Pressure TapsHouse with Pressure Taps

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Terrain ModelingTerrain ModelingBoundary layer transition will be affected by tall trees and influence windspeeds, loads, and WBD environment on one and two story residences

Z

X

Displacement Height

OpenOpen to Suburban

Transition

OceanBarrierIsland

BayBeach Town Suburban Forests Suburban

Residential –Heavily Treed

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Mean Velocity Profiles-PreliminaryMean Velocity Profiles-Preliminary

0

10

20

30

40

50

60

70

80

90

100

0 0.25 0.5 0.75 1

U(z)/Uref

Fu

ll S

cale

Hei

gh

t (m

)

Medium Density Forest - Trees Surrounding HousesMedium Density Forest - Clear Cut Around HousesLight Density Forest - Trees Around HousesLight Density Forest - Clear Cut Around HousesSuburban Terrain (Exposure B)Open Terrain (Exposure C)

Mean wind speed with height

Closely agrees with full-scale data

Medium and light density forest

Suburban (exposure B)

Open (exposure C)

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Turbulence Intensity vs HeightTurbulence Intensity vs Height

0

10

20

30

40

50

60

70

80

90

100

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

Turbulence Intensity

Fu

ll S

ca

le H

eig

ht

(m)

Medium Density Forest - Trees Surrounding HousesMedium Density Forest - Clear Cut Around HousesLight Density Forest - Trees Around HousesLight Density Forest - Clear Cut Around HousesSuburban Terrain (Exposure B)Open Terrain (Exposure C)

Fluctuations with height

Closely agrees with full-scale data

Medium and light density forest

Suburban (exposure B)

Open (exposure C)

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Task 2. Model Representative Task 2. Model Representative HousesHouses

Panhandle site visit completed

CAD modeling of houses is underway

8 Houses will be modeled and positioned at multiple locations in Panhandle

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Example Windows on One HouseExample Windows on One House

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Example Roof to Wall Connections Example Roof to Wall Connections for New Code Housefor New Code House

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Example View of Window FramingExample View of Window Framing

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Task 3, 4, and 5 StatusTask 3, 4, and 5 Status

Wind-borne debris model is being updated

Updated validation will begin in mid-February

Simulation of Panhandle homes will begin in early March (different locations and tree env.)

Goal is to have preliminary results by late March and final report in May

Results will include metrics on risk, costs, loss reduction benefits, and damage frequency with and without opening protection for model houses at various locations in the Panhandle

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Wind-Borne Debris Construction Wind-Borne Debris Construction OptionsOptions

Current requirements FBC WBD Limited to 1 Mile from Coast

Alternative WBD Code Options Evaluate WBD region by identifying border where cost = benefits

Evaluate Acceptable Protection Options Panel Shutters Accordion Shutters Impact Resistant Glazing Plywood Shutters

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Present Findings--Do Benefits Present Findings--Do Benefits Outweigh Costs?Outweigh Costs?

Benefits (Loss Reduction) Loss Reduction Differential (Compared

to FBC w/o WBD Protection) Avoided Losses = Benefits

Building Repair and Reconstruction Contents Loss of Use

Other Benefits Depends on Building, Location, Terrain

Cost of WBD Protection Increases Initial Costs Range of Protection Options

Permanent In Place Systems that Close Removable Shutters Different Materials

Depends on Building and Location

Benefits Costs

Metrics• Physical Damage• Average Annual Losses Aggregate Costs• Benefit Cost Ratio Aggregate Loss Reduction• Net Present Value Building Life (years)

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Model Validation with Measured DataModel Validation with Measured Data

Florida Coastal Monitoring Program (UF, DCA) Provides real measured pressure loads on houses during hurricanes Provides a benchmark pressure and wind speed value for roof cover

loss (roof cover provides a major source of debris)

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House Data from IvanHouse Data from Ivan

96-107 mph

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Analysis of Wind Pressure on HousesAnalysis of Wind Pressure on Houses

-4

-3

-2

-1

0

1

Inci

den

t W

ind

Dir

ecti

on

110º

Panhandle house in Isidore ’02 and Ivan ‘04

Wind tunnel pressure contours to be compared with full scale data

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Model Validation with Measured DataModel Validation with Measured Data

Sample analysis from measurements on a house duringHurricane Ivan

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Portable Weather StationPortable Weather Station

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Window Protection TestingWindow Protection Testing

Lexan window cover tested at

35 mph (code required) 45 mph 56 mph 69 mph

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Model Validation with Observed DamageModel Validation with Observed Damage

Statistical analysis of damage documented on hundreds of homes after the 2004 season

Data will be used as a benchmark for ARA model performance.

Does the model match observation?

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Model Validation with Observed DamageModel Validation with Observed DamageHomes with Window Damage by Neighboorhood Roof Cover and Window Protection :

Wind Zones 10 and 11 from Hurricane Charley (98)

50.0%

23.9%

31.3%

16.7%

9.1%11.8%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

Tile Non-tile Overall

% H

ome

s W

ith a

t L

east

One

Win

dow

Da

mag

ed

Unprotected

Protected

`

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Task 3, 4, and 5 StatusTask 3, 4, and 5 Status

Wind-borne debris model is being updated

Updated validation will begin in mid-February

Simulation of Panhandle homes will begin in early March (different locations and tree env.)

Goal is to have preliminary results by late March and final report in May

Results will include metrics on risk, costs, loss reduction benefits, and damage frequency with and without opening protection for model houses at various locations in the Panhandle