Using Flexible Loss Modelling Platforms to Develop Unique ... Arango.pdf · ©Aon Limited trading as Aon Benfield (for itself and on behalf of each subsidiary company of Aon Corporation)

Prepared by Cristina Arango and Martin Kadlec, Impact Forecasting

RAA Cat Risk Management 2020

Using Flexible Loss Modelling Platforms to Develop Unique Terrorism Risk Management Tools

Impact Forecasting | Proprietary & Confidential 2

Agenda

Section 1 IF’s Hi-Res Terrorism Blast Modelling using Computational Fluid Dynamics (CFD)

Section 2 CFD Blast model multiplatform implementation using Oasis format

Section 3 Key takeaways


IF’s Hi-Res Terrorism Blast Modelling Using Computational Fluid Dynamics (CFD)


Real Blast Testing

Karagozian & Case, Inc. https://www.youtube.com/watch?v=QRx1_nuP2Jw

https://www.youtube.com/watch?v=QRx1_nuP2Jw


IF’s Terror Blast Modelling Using CFD

Property damage and workers’

comp injuries & fatalities

.

Façade, structural damage

and collapse evaluation

.

CFD blast simulationsDB with individual building

information.

VulnerabilityHazardExposure Loss


Blast Description

3D Computational Fluid Dynamics Simulation timeline

(overpressure)

Pressure-time history can be effectively represented by two parameters:

▪ Over-Pressure (OP)

▪ Pressure Impulse (PI)


CFD Blast Modelling Approach

3D urban environment Blast simulations Outputs

▪ WALAIR software is used to perform full

3D blast simulations

▪ Uses CFD techniques – able to capture

channelling, shielding and reflection of

incident shockwave

▪ Simulation inputs:

o domain geometry

o blast location

o mass of explosive

o type of explosive

▪ Runs on Graphical Processing Units

making it faster than other comparable

software

▪ Model output includes blast metrics in 3D at

predefined model resolution (2m across the

surface of building and domain):

o Peak overpressure

o Impulse

o Pressure time history

▪ 3D urban environment is generated from

buildings’ footprints and heights datasets

▪ Structure and façade info are defined at

individual building level (IF’s own

exposure DB)

WALAIR has been validated using experimental data. Results have been published in research papers such as Nicholson A., Stirling C. G., Misselbrook N. K. – Fast running CFD code

using GPGPUs for high fidelity airblast calculations.


CFD Blast Modelling Framework

PI

OP

DR

▪ Pressure Impulse (PI) curves describe the damage caused by the blast

▪ Point-wise damage ratio (DR) from PI curves allows to evaluate:

(1) severity of façade damage and

(2) structural damage level reached and possible building collapse

PI curves for specific structural and façade types and

damage levels


▪ Extend of collapse depends on:

(1) Point-wise damage: blast (external forces)

(2) Column size/strength: building (internal forces)

▪ Workers in collapsed zones suffer mostly fatal injuries

▪ Façade damage: casualty distribution as a function of DR

Example: Workers Comp. Damage & Collapse Framework

Compute damage ratio DR @ 2m

Estimate # of failed columns

Estimate total collapse extent

Combine collapse and façade damage

Colla

pse

exte

nt

eva

lua

tio

n

> 5 columns

Localised

substantial

damage

Destruction

Perimeter above column collapse threshold

Extended collapsed area

Façade only damage

Transition zone/collapse buffer

Up to 2 columns

Casualty

Dis

trib

ution

Damage Ratio

Fatal

PPtotal

PPmajor

PPminor

TempTotal

MedOnly

Façade

Damage only

range


Case Study: CFD Terrorism Blast Model for New York

IF’s own exposure DB defines 3D cityscape & individual building data

Property module: Buildings, Contents and BI

Worker’s comp module: Worker’s comp. injuries/fatalities

Blast location uncertainty: densely placed targets at every

street’s intersection and midpoint

Explosive size uncertainty: 2, 5 and 10 ton blast

Workers location within a building are randomized

CFD modelling to capture complex blast wave-urban

environment interaction

Blast metrics (pressure and impulse) at 2m resolution on

building’s surface

Considers buildings’ structural resistance to blast and collapse

potential:

▪ Façade only and structural damage

▪ Different collapse criteria for property and workers’

compensation modelling

Damage &

Collapse

CFD blast

simulations

Uncertainties

Exposure DB

and model

scope


Model Implementation Using Oasis Format


Oasis Model Format in ELEMENTS

ELEMENTS allows Oasis formatted models to be hosted:

▪ Hazard and vulnerability in Oasis format

▪ Exposure in ELEMENTS format

▪ ELEMENTS loss calculation engine

Enhanced Oasis model format in ELEMENTS for:

▪ High resolution flood models

▪ Secondary perils

Greater model interoperability:

▪ 3rd party models in Oasis format can be implemented in

ELEMENTS

▪ IF models in Oasis format can be deployed in Oasis LMF,

ModEx or client’s Oasis environment

Implementation in ELEMENTS

ELEMENTS

production ready

platform

Oasis hazard /

vuln files ELEMENTS Oasis

database

ELEMENTS

Client

Model

Development

Model is ready for

operation on production

ELEMENTS platform

Development

following Oasis

model format

Files transferred

into Oasis DB


Oasis Model Format in ELEMENTS

Hazard

Information

Vulnerability

Information

Each model has its own database

▪ All hazard and vulnerability information are stored in tables

▪ Table design is the same for both probabilistic and deterministic/scenario models

EventInfoEventID

Frequency

EventFootprintCount

DemandSurge

Region

Intensity

….

EventFootprintEventID

MastertableID

IntensityBinIndex

Probability

….

HazardIntensityBinIntensityBinIndex

BinFrom

BinTo

….

VulnerabilityDamageFunctionID

IntensityBinIndex

DamageBinIndex

Probability

….

DamageBinDamageBinIndex

BinFrom

BinTo

….


Oasis Model Format Implementation – Model Developer’s View

Key questions to answer

Can the format handle the model complexity?

Hazard

How to measure the hazard?

Is the measure relevant for all

coverages?

How to discretize it?

Vulnerability

How to discretise damage ratio

into bins?

What options/modifiers should be

considered?

Loss

What is the definition of the risk –

SI vs. # workers, pay-outs


Property

Building

▪ Uses a single damage ratio

per building and blast

scenario

▪ Straightforward

implementation in Oasis

format

Property BI

▪ Uses building damage ratio

and distance from the blast

▪ Moderate complexity of

implementation in Oasis

format

Workers

Comp.

▪ A function of building

damage, workers position

within building and injury

class

▪ More complex

implementation utilising

Oasis format flexibility

Oasis Model Format Flexibility – 3 Examples


Example 1: Property Building Damage – Coupled Hazard & Vulnerability

▪ Hazard quantity is building level damage ratio (BDR):

– Construction and façade type modifiers embedded in BDR – taken

from model building DB

▪ Vulnerability defined as 1:1 mapping with hazard (customisable)

▪ No building properties are required in portfolio for modelling

▪ Oasis format flexibility supports this scheme

▪ Deterministic event set

▪ Thousands of blasts locations

with different explosive sizes

▪ 3D fields for 2 hazard metrics:

overpressure OP and pressure

impulse PI

▪ Vulnerability/PI curves in terms

of 2 hazard metrics: OP and PI

▪ Construction and façade type

specific

Event set Hazard Vulnerability

Implementation:

Coupled hazard & vulnerability

▪ Risk lat/lons mapped to model

building ID

▪ Embedded building properties

DB (structure and façade)

Exposure


Evacuated zone

▪ Measure: distance from blast center

▪ Discretized into M classes:

– <100m

– <200m

…

– >1km

Damaged offices, shops, etc.

▪ Measure: building level damage ratio BDR

▪ Discretized into N classes:

– no damage

– broken glazing

…

– total collapse

Example 2: Property Business Interruption BI – Hazard

All combinations are possible (almost), 2-dimensional hazard (matrix N x M)

Oasis format requires “flat” hazard table. Implementation solution: matrix de-pivoted into vector of hazard

bins representing each combination

Property

BI

Direct

Property

BI

Indirect


Example 2: Property Business Interruption – Vulnerability

Damage bins

Damage uncertainty

Vulnerability matrix

− Example: Building with broken glazing 300 m from blast center: closed for 3 months, DR 0.25

− Building, content and business interruption are implemented as one model with multiple

coverages to allow proper application of financial conditions

▪ Each hazard case (bin) may be assigned to more bins with certain probability

▪ Currently implemented as deterministic

▪ Each bin may have a range of damage ratio to sample from

▪ Implemented with fixed damage ratio 0/12, 1/12, … 12/12

▪ 13 damage bins representing BI for 0, 1, … 12 months

▪ Sum insured assumed to represent payout for a year lasting BI


Risk value defined by

sum insured (SI)

vs


number of workers

Loss (GU) = DR x SI

vs

Loss (GU) = ∑payouts

Damage ratio (DR)

relative to SI

vs

Payout per worker -

depending on injury class

Example 3: Workers Compensation

Oasis does not directly support workers compensation exposure and payout calculations.

Differences between property and workers compensation modelling

Exposure Vulnerability Loss



sum insured (SI)

vs

Worker defined by

“virtual” value (VV)

Loss (GU) = DR x SI

vs

Loss (GU) = PR x VV

Damage ratio (DR)

relative to SI

vs

Payout ratio (PR)

relative to VV

Example 3: Workers Compensation – Redefining the Approach

We can now use standard Oasis model format to calculate workers comp. losses

Redefinition of workers compensation modelling approach

Exposure Vulnerability Loss


▪ Collapsed zone

▪ Façade damage

▪ Measure: pointwise damage

ratio

▪ Defines injury profile for each

damage ratio

▪ Applied on all building points

provides distribution of injury

classes for whole building

▪ Represents probabilistic

distribution of injury classes for

single worker in given building

and scenario

Example 3: Workers Compensation – Implementation

Building hazard profile Casualty matrix Oasis hazard table

Casualty D

istr

ibutio

n

Damage Ratio

Fatal

PPtotal

PPmajor

PPminor

TempTotal

MedOnly

+ Final injury distribution includes location uncertainty

− Exposure (total workers per building) has to be disaggregated - else workers’ location

is random but correlated

Hazard (building hazard profile) and vulnerability (casualty matrix) are again coupled to create Oasis hazard table


Example 3: Workers Comp. Model in Oasis – Key Implementation Points

▪ Probability to fall into one of

the injury classes for a

worker randomly positioned

within building

▪ Exposure has to be

disaggregated

▪ Worker represented by virtual

value (VV)

▪ Damage ratio represented by

payout ratio (payout relative

to worker virtual value VV)

▪ Sum of payouts – each injury

class represented by payout

ratio multiplied by worker

virtual value (VV)

Implementation not straightforward, but successful!

Workers comp. model in

Oasis model format


IF CFD Terrorism Blast Model in Oasis format – Inputs and Outputs

▪ Risk location (latitude & longitude)

▪ Sums insured

▪ Policy conditions

Property Workers Compensation

Model

built-in

features

Exposure

data

Loss results

▪ Risk location (latitude & longitude)

▪ Head count/number of workers per building/floor

▪ Policy conditions

▪ Risk latitude & longitude mapped to closest building ID using IF’s exposure DB

▪ Building properties/modifiers assigned from IF’s exposure DB

▪ If workers/floor are unknown, total workers/building are dis-aggregated based on floor footprint area

▪ Occupancy rate (default is 100%)

▪ Pay-outs per injury class (can be customised)

▪ 2, 5 and 10 ton blast scenarios

▪ Property loss per blast

▪ Property loss per blast & building ID

▪ Other breakouts (e.g. coverage)

▪ Workers’ comp loss per blast

▪ Workers’ comp loss per blast & building ID

▪ Other breakouts (e.g. per building ID & injury

class)


Key Takeaways


Key Takeaways

Can “non-standard” models be implemented in Oasis format?

Implementation not always straightforward, but possible

Oasis files

structure

Exposure needs

Hazard and

vulnerability

definitions

Solution

Sta

rt

Fin

ish

Making a decision on

what to implement as

“hazard” and

“vulnerability”

Assessing if Oasis

format/file structure

can accommodate

modelling needs

Assessing if exposure

characteristics can be

represented

Develop a technical

solution for model

implementation

Testing

Testing results

throughout model

development cycle


Contacts

Martin Kadlec

Impact Forecasting Prague

[email protected]

Cristina Arango

Impact Forecasting London

[email protected]

mailto:[email protected]

mailto:[email protected]


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Using Flexible Loss Modelling Platforms to Develop Unique ... Arango.pdf · ©Aon Limited trading as Aon Benfield (for itself and on behalf of each subsidiary company of Aon Corporation)