hurricane vulnerability assessment: latest experience and ... #5/6_pinelli.pdf · september, 2010...

September, 2010 IDRiM 2010

Hurricane Vulnerability Assessment: Latest Experience and Development in the Florida

Public Hurricane Loss Model

1st Annual Conference of the International Society for Integrated Disaster Risk Management

Kurt Gurley Kurt Gurley

JeanJean--Paul Pinelli, Gonzalo PitaPaul Pinelli, Gonzalo Pita


Florida


Agenda

• History• FPHLM: objectives, goals, and purpose• FPHLM engineering module overview• Conclusions


Turning Point

• Hurricane Andrew in 1992 was a wake up call

• $16 billion in insured losses and $26.5 billions in total losses expressed in 1992 dollars


Pre-Andrew Building Codes

• Building codes adopted starting in the 1940’s

• South Florida Building Code in Miami area• Southern Building Code in rest of the state• Poor compliance and enforcement• Myriad of different jurisdictions


Pre-Andrew Econometric Models

• Belief whole hurricane hazard situation lay exclusively within the actuarial field and could be managed with actuarial information alone

• relied up to the 1990’s solely on recent historical claim data

• Excess Wind Procedure• Model predicted $80 million for 1992 clearly less than the

$16 billion insured losses that Andrew caused (Musulin, 1997).


Solution?


Post Andrew State Response

• South Florida Building Code (1994) and Florida Building Code (2001)

• Citizens Property Insurance Corporation– State insurer of “last resort”

• Florida Commission on Hurricane Loss Methodology– established to mediate between the insurance industry

and the state of Florida, to set a method for the rate filing process and to review and certify the loss models

• Florida Public Hurricane Loss Model


Agenda



Florida Public Hurricane Loss Model

• Funded by the Florida Office of Insurance Regulation.

• Administered through the International Hurricane Research Center at FIU - Project manager: Shahid Hamid http://www.cis.fiu.edu/hurricaneloss/index.html

• Multidisciplinary effort involving several institutions: FIT, FIU, FSU, NIST, NOAA, UF, UM

• Certified by the Florida Commission on Hurricane Loss Methodology in 2007, 2008, and 2009, http://www.sbafla.com/methodology/index.asp


Objectives of the FPHLM

• “Develop a public model to determine hurricane risk and project losses to assure appropriate insurance rate regulation”

• Provide an alternative to commercial proprietary models which are NOT open to public scrutiny

From http://www.edf.org/article.cfm?contentid=5363


Goals of the FPHLM

• To assess hurricane risk, and to predict annual expected insured residential losses for specific sites, zip codes, counties and regions in Florida (stochastic analyses).

• To predict insured losses for scenario analyses either user defined scenarios or historical events.

• To estimate insured losses for entire portfolios of residential / commercial-residential properties.


Agenda



Public Model Overview

ProgrammingModel

MeteorologyModel

Provides probabilistic or scenario wind field info

EngineeringModel

Given wind, predicts damage

ActuarialModel

Filters damages into insured losses


Engineering Research Team


Research Objectives

Determine types Quantify wind resistanceTranslate wind speed into loads

Monte Carlo Simulation

% Quantify damages


FLORIDA EXPOSURE


3 major residential building categories

• 1. Single Family Homes• 2. Manufactured (Mobile) Homes• 3. Condominium and apartment buildings

– Low-rise (1-3 stories)– Mid-rise (4+ stories)


Typical Single Family Home Distribution in Florida


Manufactured Homes


Low-rise residential


Variety of mid/high-rise buildings


Wind DamageLow-rise vs. mid/high-rise

• Low-rise buildings including single-family-homes– Can be categorized in a few typical generic buildings– Can suffer substantial external structural damage (in addition to envelope

and interior damage) including complete collapse– Modeling approach : the building is modeled as a whole

• Mid-rise buildings– They are highly variable in shape, height, material, etc– Cannot be categorized in a few generic building types– Engineered structures that suffer little external structural damage and are

unlikely to collapse– Can suffer extensive cladding and opening damage leading to water

penetration and interior damage– FPHLM adopts a modular approach : the building is treated as a

collection of apartment units


Closed Building Open Building

Mid-high risebuildings characterization


Mid-high rise building characterization for Modular Approach

Opening Type Unit Type Quantity Dimensions

[ft] Corner / Closed 5 5 x 4 Corner / Open 8 5 x 4

Middle / Closed 2 5 x 4 Windows

Middle / Open 5 5 x 4 Entry Door All 1 8 x 4

Sliding Door All 1 8 x 8

Apartment types according to location

Number of openings per apartment type


Different modules based on:

• Building layout (open/closed)• Position of the apartment (Corner/middle)• Base area

• Story height (debris hazard)

• Opening type

• Exterior wall type

Possible cases: ~2048

Mid-high riseApartment modules definition


Research Objectives



% Quantify damages


Wind Speed External Wind Load

• Translate wind speed into pressures and forces on the exterior of the whole building (low-rise) or on the façade of the apartment modules (mid/high-rise)


Component Wind Loads

InputDiscrete 3 sec

wind speed(e.g.V = 110 mph)

OutputComponent

loads/pressures(e.g. one sheathing panel)

• Data Sources:– Wind load provisions in code

(ASCE-7-05)– Directional modifications– Wind tunnel corrections– Full scale measurement

• Influences:– Building shape– Wind direction


• Probability of window breakage due to debris modeled by exponential cumulative distribution function

– A =Fraction of potential missile objects in the air– NA = Total # of available missile objects – B= Fraction of airborne missiles that hit the house – C= Fraction of the impact wall that is glass – D= Probability of momentum above damage threshold

• Parameters calibration based in large part on post storm field studies of residential damage

• Applied to each window on model house

]****exp[1)( DCBNAVp AD −−=

Wind-borne Missiles


Model Components



% Quantify damages


Component Resistance to Wind

• For each structural type or apartment unit type– Identify major

components– Model the capacity of

each component– Determine Load Paths


Low-Rise Buildings Components

• Type: e.g., Concrete Block, Gable Roof

• Selected components– Roof cover– Roof sheathing– Overhang– Gable end trusses– Roof to wall connections– Wall covering– Wall sheathing– Openings: windows, sliding

doors, entry doors

Openings

Roof SheathingRoof Cover

Roof to Wall Connections

WallsOpenings

Roof SheathingRoof Cover

Roof to Wall Connections

Walls


Mid/High-Rise BuildingsModular Unit Components

• Type: e.g., Closed building, Corner Unit, No shutters, 16 windows

• Selected components– Pressure Windows– Impact Windows– Pressure Entry Door– Impact Entry Door – Pressure Sliding Door – Impact Sliding Door


Model Components



% Quantify damages


Research Goal

Create a probability-based system response model to:

1. Simulate the performance and interaction of the components of typical Florida buildings

2. Evaluate their vulnerability during interaction with hurricane winds


Example Damage Matrix

Partial output file : each row corresponds to 1simulation; eachcolumn to a component; there are 32 columns for low-rise matrices

Building Concrete block, gable roof, no shutters Wind 150 mph 3-sec gust, 45º to axis


Damage matrix sample result

Exte

rior D

amag

e

Wind Speed [3sg – mph]


Model Components



% Quantify damages


Vulnerability Model %

• From the Damage Matrices– Convert modeled physical damages into damage

ratios = repair cost/(home or unit value)– Define the vulnerability of different building or

unit types = P(damage|wind speed)– Provide a logical method for prediction of damage

to other coverages– Validate the damage predictions


Damage Modeling

Exterior

Damage

Stage 1

Building Damage

Leaks

Water penetration propagation

Interior & Utilities Damage

Stage 2 Stage 3

Contents

Damage

Time Element

Coverage

Scientific/experimental relationships based on the physics of the problem


Issues:• Interior damage is a substantial part of the overall

damage• Interior damage is a function of exterior damage• Interior damage is caused mainly by water intrusion.

Solution: scientific and engineering based model• Assess damage on envelope components• Estimate rainfall rate and duration• Calculate impinging rain• Compute water intrusion through breaches• Transform water into interior damage

Interior Damage Model


Buildings Vulnerability New Interior Damage Model

Plot Exterior vs. Interior damage curve for

component “i”

Transform Water contents (including vertical propagation) to Interior Damage

Load wind-borne breach area and existing defects breach area

For a given wind speedVW

Breach area AB(VW)

Defect Area AD(VW)

Estimate rainfall rate IV

Estimate rain duration dR

Convert vertical to horizontal rainfall rate IH

Water that enters the building through the breach is

( )BDRFVI A,A,d,C,IW f=

Increase velocity to VW = VW + 5 mph and

repeat loop

2

3

4

6

5

7

8

9

For a given Damage mode “i”

1

Last VW? Yes

No

Go to next damage mode and repeat loop

11

Inte

rior D

amag

e

Water

Con

vers

ion

fact

or C

F

Wind speed

Duration

10


RAIN INTRUSION MODELRainfall rate and duration statistics

Rainfall rate (Beta-Tanh pdf)

Rain duration (Wakeby pdf)

Sources: NOAA and Prof. Jiang (FIU)Sources: NOAA and Prof. Jiang (FIU)

Building Interior Damage Model

AAWE’10 – Marco Island, FL


Transform vertical rainfall rate to impinging rain to the building

From Blocken, 2009, Straube 2000 Willis & Tattelman (1989)

Raindrop diameter distributions

Building Interior Damage Model

Straube and Burnett Approx. Method

Rain Admittance

Factor (RAF)


Low-Rise Interior Damage Assessment

Example of proposed interior model


Interior Damage as a function of Wind Speed ‒ per component


Low-Rise Buildings Vulnerability General Flowchart

Select Building

Type

Load Exterior Damage ArrayDA(l,comp.,α,VW )

Span Exterior Damage ArrayWind speeds: VW = 50:5:250

Angles: = 0 : 45 : 315

Estimate Total & Component

Costs

EstimateExterior Damage

Estimate Interior &

Utilities Dam.

Calculate Total Vuln.Aggregate Exterior +

Interior Vuln.

Damage Estimation

END


Vulnerability Matrices

• Each column is a pdf of damage for a particular wind speed = probability(damage|wind speed)


Vulnerability Curves for Mid-high rise Individual Apartments types


MC

MC

aaaa

++

= MC VVVA

Exterior Damage Estimation Interior Damage Estimation

Mid/High-Rise Buildings Modular ApproachDamage Flowchart


Mid/High-Rise

Expected Damage

Flowchart

IDStories#

ID(1)... ID(7) ID(8)EIDR +++=

MC

MC

aaaa

++

= MC VVVA

Stories# )VA(W... )VA(W )VA(WEEDR 11-nn +++

=

Wal

lsD

oor

Slid

ers

Win

dow

s

Rai

nfal

l rat

ein

/hr

[ ] Bldgee V)EIDRk(1EEDRkEDV ⋅−+=


Agenda

• History• FPHLM: objectives, goals, and purpose• FPHLM overview• Conclusions


Conclusions

• In response to Andrew catastrophic losses, Florida has embarked in an aggressive hurricane risk assessment and mitigation policy.

• The Florida Public Model is an important tool in that effort.

• The Florida Public Model is a state of the art catastrophe model whose latest developments include:– A new model for the prediction of interior damage due to

rain.– A modular approach for the vulnerability modeling of

mid/high rise building of any shape and height.


Acknowledgement

• This research is supported by the State of Florida through a Department of Financial Services (FDFS) grant to the Florida International University International Hurricane Research Center. The opinions, findings, and conclusions expressed in this presentation are not necessarily those of the FDFS.

hurricane vulnerability assessment: latest experience and ... #5/6_pinelli.pdf · september, 2010...

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