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Damage Investigation Following Hurricane Irma in Florida

David O. Prevatt, Ph.D.Kurtis R. Gurley, Ph.D.

Chris Ferraro

9 October 2017Tallahassee, FL

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Outline of Presentation

• Hurricane Irma Description & Florida Impact • UF’s Damage Survey Protocol & Participants• Irma’s Peak Winds & FBC Design Wind Speed • Preliminary Damage Observations (Exterior)• Summary and Next Steps

Hurricane Irma’s Impact in Florida

• Landfall in Two landfalls on Florida:– Cudjoe Key, FL à 106 mph gust wind speed at Big Pine Key (9/10/17)– Marco Island à 130 mph (9/10/17: 3:35 pm) at Police Department

• Affected Florida from 10 – 12 Sept. 2017– 116,000 persons in 530 shelters– 11 fatalities (including 8 elderly persons in nursing home AC accident)– Power loss affects ~ 3 million customers– Storm surge and flooding in Miami, the Keys, Everglade City and Naples

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3-sec gust wind speed contour Map (Applied Research Assoc.)

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State of Florida’s Design Wind Speed

Category II (3-sec. gust)

UF Damage Assessment Survey • Objective: To Investigate structures in regions experiencing hurricane force

(Cat 3 wind speeds) • Focus à mainly single family houses, some multi-family

– Wind damage– Water intrusion– Storm Surge effects

• Approach:– Ground survey used smartphone app: Fulcrum (www.fulcrum.com)– Aerial survey of specific areas– Conducted in 5 days – 9/12 – 9/17

• Collaborated with National Science Foundation RAPID survey – Led by Notre Dame University– Researchers from FIU (Miami) and FIT (Melbourne), Auburn University– International: James Cook University (Australia), Western University (Canada)

• Coverage: 1,100 structures – 5,000 photographs of exterior building damage– 3D Point Clouds and information on structures

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Data Collection Methodology• Modified Applied Technology Council ATC-20 survey form on smartphone app• All data collected and stored in central server • Photographs and data uploaded once app is synced• GPS location automatically established and address autofilled

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Sample Fulcrum Database

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Wind Speed Estimates & FBC Design Wind

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Jacksonville &St Augustine

Miami

Marco Island

Islamorada to Key West

Naples

Fort Myers

Everglades City and Chokoloskee

Preliminary Surveys

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Jacksonville &St Augustine

Miami

Marco Island

Islamorada to Key West

Naples

Fort Myers

Everglades City and Chokoloskee

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State of Florida’s Design Wind Speed

Category II (3-sec. gust)

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Damage Observations

Jacksonville, St. Augustine: • Tornado touchdown – wind speed 130 mph• Coastal erosion along AIA highway• 46 structures surveyed• Most damage moderate

House #1Yr Built: 1982

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Extensive roof structure damage (from 130 mph tornado)

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Soil erosion due to storm surge and wave action

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Underpinning

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Miami:• Estimated wind speed: 83 mph• Generally minor roofing damage • Failed ridge caps on clay tile roofs • 19 structures surveyed

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House #2 Yr Built: 1968 (Ridge Cap Damage)

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Naples:• Estimated wind speed: 100 mph• Minor roof damage observed on roof cover• Severe roof damage to mobile homes• Minimal damage to site built structures• 83 structures surveyed

Mobile Homes

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Damage to Structures in Naples, FL

Stick Built Homes

Mobile Homes

Site Built Houses

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House #3, 4 & 5Yr built: 1984

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House #6: Yr Built: 2001(Asphalt Shingle Roof Damage)

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Marco Island:

• Estimated wind speed: 108 mph• Minor roof damage observed on roof cover• Houses have high quality.• 215 structures surveyed

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House #7: Yr Built: 1970(Asphalt Shingle Roofing Damage)

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House #8: Yr Built: 2002(Clay Tile Roof Damage)

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Value of Aerial Surveys

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Damaged clay tile roof on 10-story condominium, Marco Island

Wind Damage Assessment: Example ApplicationsHurricane Irma 2017: Gr0und and aerial

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Storm Surge Damage

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Everglades City:• Estimated wind speed: 110 mph• severe storm surge • minor wind damage on roof cover• 83 structures surveyed

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House #10(Minimal exterior damage

Severe storm surge damage)

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House #10(Interior photo showing

damage from storm surge)

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House #11(Failed masonry piers)

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Chokoloskee:• Estimated wind speed: 110 mph• severe storm surge • minor roof cover and wall cladding damage• 40 structures surveyed

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House #14(Minor wind damage, Big Pine Key)

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House #14(Interior photo for

house in Big Pine Key)

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House #14(storm surge inside)

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House #12(Vinyl siding damage)

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Islamorada to Key West:• Estimated wind speed: 116 mph• Wide spread roof cover damage• Also storm surge damage widespread• by FIU and FIT researchers • 513 structures surveyed

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House #13: Yr Built: 2007(Vinyl siding & asphalt shingle roof damage)

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Analysis

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1. WindLoad ∝ WindSpeed /(𝑖𝑠 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑎𝑙 𝑡𝑜)

DEFINITION: Windloadratio =ActualWindLoad𝐷𝑒𝑠𝑖𝑔𝑛𝑊𝑖𝑛𝑑𝐿𝑜𝑎𝑑

3. WindLoadRatio = QRSTUVWXYZ[\]]Z^_`abcdacefg__e

/×100%

• Next Slide à Comparing Actual Load vs. Design Load(approximately based on wind speed)

Structural Damage to Wind Speed Relationship

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State of Florida’s Design Wind Speed

Category II (3-sec. gust)

Surveyed RegionExample House

NumberZip Code of

HousesDegree of Damage Year built

Actual Wind Speed(3-sec peak gust )

Design Wind Speed

(Category II)

Wind Load

Ratio (%)

Jacksonville and St Augustine 1 FL 32080 Severe

(Tornado) 1982 130 (EF2 Tornado) 132 97

Miami 2 FL 33135 Minor 1968 83 168 24

Naples3, 4 and 5 FL 34113 Severe

(Mobile Homes) 1984 100 166 36

6 FL 34113 Minor 2001 100 166 36

Marco Island7 FL 34145 Minor 1970 108 169 41

8 FL 34145 Minor 2002 108 169 41

Everglades City

9 FL 34139 Moderate — 110 163 46

10 FL 34139 Severe(surge) — 110 163 46

11 FL 34139 Moderate(surge) — 110 163 46

Chokoloskee 12 FL 34141 Moderate — 110 164 45

Islamorada to Key West

13 FL 33042 Moderate(wind & surge) 1998 116 180 42

14 FL 33043 Moderate(surge) — 116 180 42

Wind Load Ratios & Damage at Survey Sites

Summary & Next Steps• Hurricane Irma was not a design level wind event

• Wind loads ranged from 25% to 97% of design levels• More vulnerable structures in North-Central Florida (lower design wind speeds)

• The question: Should any structures have failed?• Florida structures generally performed okay • The more severe damage more likely in older structures

• However, our preliminary survey à exterior damage only• Storm surge damage & costs high in low-lying areas• Future Work Proposal:

• Conduct interview with home owners to:• Capture & quantify distribution and extent of interior damage• Estimate of repair costs & time and evacuation

• Assess homeowner opinions on retrofit & strengthening home• Capture effects of water intrusion & storm surge

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AcknowledgementWe gratefully acknowledge financial support of the Florida Building Commission

We wish to acknowledge the National Science Foundation RAPID Award through Notre Dame University

Researchers and Student Participation: • Florida International University (Miami, FL)• Florida Institute of Technology (Melbourne, FL)• University of Western Ontario (Canada)• James Cook University (Australia)• Auburn University

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Thank You and Questions?

David O. Prevatt@davidprevatt2