Climate model-based probabilistic wind risk assessment under future climate

Kazuyoshi Nishijima

Associate Professor of Engineering Decision Analysis

CERDA

18/05/2012 Bristol/Cabot-DPRI workshop 3 DTU Civil Engineering, Technical University of Denmark

CERDA – Areas and current focuses

Natural hazard risks Decision analysis

Climate change

• Wind hazard

• Wind vulnerability

• Flood vulnerability

• Real-time decision optimization

• Reliability in economics

• Life safety

• Assessment

• Adaptation

Structural reliability theory

• Bayesian networks

• Scaled probability integral

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Question to answer

Frequency vs. Intensity

Wind-induced residential building risk increases?

Typhoon

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Inputs

Hazard modeling

• AGCM simulation results within the KAKUSHIN program

• Probabilistic modeling methodology for typhoon events

Fragility modeling

• Damage report for the typhoon Songda in 2004

• Wind field simulated with JMA-NHM and JMA-RANAL/JMA-RSM

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Hazard modeling

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Extracted typhoons

Current climate:1979-2003 Projected future climate:2075-2099

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Not enough typhoons for risk assessment…

Monte Carlo simulation with probabilistic typhoon model!

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Probabilistic modeling of typhoon events

AG

CM

sim

ula

tion

results

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Occurrence model

• Re-sampling

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Transition model

• Temporary spatially inhomogeneous Markov model

• Translation speed

• Translation angle

• Central pressure

• Radius of maximum wind speed

Model for each 5°x 5°grid and month.

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• Wind field at gradient height

Given

- Central pressure

- Translation speed/angle

- Radius of maximum wind speed

Wind speed [m/s]

Wind field model

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• Empirical relation

Surface friction model

Considering

• Topography

• Land use

,u r

Surface wind speed

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Simulated surface wind speed

• Maximum wind speeds during a typhoon event

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Monte Carlo simulation

AGCM simulation

25 years

Monte Carlo simulation

25000 times of 1-year

x1000!!

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Fragility modeling

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Damage ratio

(Degree of damage is not differentiated.)

Reported damage ratio of residential buildings

Kyushu island in Japan

0 50 100 km

Tomokiyo et al. (2009)

(# of damaged buildings)

(# of total buildings)

18/05/2012 Bristol/Cabot-DPRI workshop 27 DTU Civil Engineering, Technical University of Denmark

Computation of wind field by Songda

• Japanese 25-year Reanalysis (JRA-25)

• JMA Non Hydrostatic Mesoscale Model (JMA-NHM)

Large scale 5km mesh Small scale 1km mesh

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Computed wind field and pressure fields

[m/s]

50

25

0

[hPa]

Wind speed/direction Sea level pressure

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Combining these

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Fragility model

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Hazard assessment

1

0.86

1.04

1

0.95

1.13

Decrease

Increase

Decrease

Increase

Mean value 98-quantile

(50-year wind)

• Change of annual maximum wind speed statistics

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The answer

(Projected future climate)

(Current climate) = 0.87*

* Simple average over 2249 locations in Japan

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Are you happy?

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Research agenda

(1) Improved fragility/vulnerability model

Design wind speed: around 30-35m/s in main Japanese islands

18/05/2012 Bristol/Cabot-DPRI workshop 35 DTU Civil Engineering, Technical University of Denmark

Research agenda

• A failure mode

Debris

Roofing

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Research agenda

• Hybrid (statistical + engineering) approach

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Research agenda

(1) Improved fragility/vulnerability model

(2) Improved wind field model

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Thank you for your attention!