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Unit VII

Explosive Blast

BUILDING DESIGN FOR HOMELAND SECURITY

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-2

Unit Objectives

Explain the basic physics involved duringan explosive blast event, whether byterrorism or technological accident.

Explain building damage and personnelinjury resulting from the blast effects upon abuilding.

Perform an initial prediction of blastloading and effects based upon incidentpressure.

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-3

Unit VII: Explosive Blast

Units I-VI covered the Risk AssessmentProcess

Units VII and VIII explain Explosive Blast,

CBR Agents, and their effects

Units IX and X demonstrate techniques forsite layout and building design to counter

or mitigate manmade threats and similartechnological hazards

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-4

Blast Loading

FactorsExplosive properties

Type

Energy output(TNT equivalency)

Quantity

FEMA 427, Figure 2-1: Schematic of Vehicle Weapon ThreatParameters and Definitions, p. 2-2

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-5

Typical Incident Pressure Waveform

FEMA426, Figure 4-1: Typical Pressure-Time History, p. 4-2

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-6

Reflected

Pressure

Equivalent pressure occurs at Scaled Distance =

Distance / (Net Explosive Weight, TNT equivalent)1/3

Incident and Reflected PressureBlast energy lost at rate of volume increase in X, Y, and Zdirections

IncidentPressure

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-7

Reflected Pressure/Angle of Incidence

FEMA 426, Figure 4-2: Reflected Pressure Coefficient vs.Angle of Incidence, p. 4-3

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-8

Typical Blast Impulse Waveform

FEMA 426, Figure 4-3: Typical Impulse Waveform, p. 4-4

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-9

Blast Loading Factors

Location of explosiverelative to structure

Stand-off distance

Reflections andreflection angle

Ground

Buildings

Identify worst case

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-10

Blast Compared to Natural HazardsHigher incident pressures and relatively low impulse

High explosive (C-4)

Low-order explosive(ANFO)

Aircraft or vehicle crashcombines kinetic energy(velocity, mass), explosiveloads, and fuel/fire

200 mph hurricane generates only 0.8 psi, but withvery large impulse

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-11

Blast Compared to Natural HazardsDirect airblast causes morelocalized damage

Component breakage Penetration and shear Buildings other side farther away Reflections can increase damage

on any side

Greater mass historically usedfor blast protection

Greater mass usually detrimentalduring earthquake due to resonance

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-12

Factors Contributing to Building

DamageFirst approximations based upon:

Quantity of explosive

Stand-off distance between building andexplosive

Assumptions about building characteristics

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-13

Types of Building Damage

Direct Air Blast

Component failure Additional damage after breaching

Collapse

Localized

Progressive

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-14

Blast Pressure Effects

FEMA 426, Figure 4-4: Blast Pressure Effects on a Structure, p. 4-7

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-15

Blast Pressure Effects

FEMA 426, Figure 4-4: Blast Pressure Effects on a Structure, p. 4-7

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-16

Blast Pressure Effects

FEMA 426, Figure 4-4: Blast Pressure Effects on a Structure, p. 4-7

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-17

Causes of Blast Injuries

Overpressure Eardrum rupture Lung collapse/failure

Blast Wave

Blunt trauma, lacerations, and

impalement

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-18

Causes of Blast Injuries

Fragmentation

Bomb or vehicle

Street furniture or jersey barriers

Building component failure

Glass predominant Walls

Floors

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-19

Murrah Federal Building, Oklahoma City

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-20

From Journal of American Medical Association, August 7, 1996

The majority of

deaths were due to

the collapsing

structure

Murrah Federal Building, Oklahoma City

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-21

Murrah Federal Building, Oklahoma City

From FEMA Oklahoma City Bombing Report 9-0300 / FEMA 277,August 1996

1.8 square miles

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-22

PotentialInjury

Potential Door andGlazing Hazards

PotentialStructural Damage

Levelof Protection

Levels of ProtectionCONVENTIONAL CONSTRUCTION INCIDENT OVERPRESSURE

Majority of personnel indamaged area suffer minorto moderate injuries withpotential for a few serious

injuries, but fatalitiesunlikely. Personnel outsidedamaged areas willpotentially experienceminor to moderate injuries.

Glazing will fracture,potentially come out offrame, but at reducedvelocity, does not present

significant injury hazard.(Very low hazard rating)Doors may fail, but willrebound out of frames,presenting minimal hazards.GSA 3a

Moderate damageBuilding damage will not beeconomically repairable.

Progressive collapse willnot occur. Space in andaround damaged area willbe unusable.

Low

psi = 2.3

Majority of personnel indamaged area suffer

serious injuries withpotential for fatalities.Personnel outsidedamaged area willexperience minor tomoderate injuries.

Glazing will break and likelypropelled into building,resulting in serious glazingfragment injuries, butfragments will be reduced.Doors may be propelled intorooms, presenting serioushazards. GSA 4

Heavily damaged - onset ofstructural collapse. Major

deformation of primary andsecondary structuralmembers, but progressivecollapse is unlikely. Collapseof non-structural elements.

Very Low

psi = 3.5

Majority of personnel incollapse region sufferfatalities. Potentialfatalities outside collapsedarea likely.

Doors and windows will failcatastrophically and resultin lethal hazards. (Highhazard rating) GSA 5

Severe damage. Progressivecollapse likely. Space in andaround damaged area will beunusable.

Below ATstandards

FEMA 426, Adapted from Table 4-1: DoD Minimum Antiterrorism Standardsfor New Buildings, p. 4-9, updated with UFC 4-010-01, 22 Jan 2007

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-23

PotentialInjury

Potential Door andGlazing Hazards

PotentialStructural Damage

Levelof Protection

Levels of ProtectionCONVENTIONAL CONSTRUCTION INCIDENT OVERPRESSURE

Only superficial injuriesare likely.

Glazing will not break. (Nohazard rating) Doors will bereusable. GSA1

Minimal damage. Nopermanent deformations.The facility will beimmediately operable.

High

psi = 1.1

Personnel in damaged areapotentially suffer minor tomoderate injuries, butfatalities are unlikely.Personnel outside damagedareas will potentially

experience superficialinjuries

Glazing will fracture, remainin frame and results inminimal hazard consisting ofglass dust and slivers.(Minimal hazard rating) Doorswill stay in frames, but will not

be reusable. GSA 2

Minor damage Buildingdamage will be economicallyrepairable. Space in andaround damaged area canbe used and will be fullyfunctional after cleanup and

repairs.

Medium

psi = 1.8

FEMA 426, Adapted from Table 4-1: DoD Minimum Antiterrorism Standardsfor New Buildings, p. 4-9, updated with UFC 4-010-01, 22 Jan 2007

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-24

Nominal Range-to-Effect Chart

FEMA 426, Figure 4-5: Explosive Environments BlastRange to Effects, p. 4-11

25

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-25

YIELD (TNT Equiv.) 4,000 lb.

Reflected PRESSURE 9,600 psi.

Stand-off 15 feet

YIELD (TNT Equiv.) 20,000 lb.Reflected PRESSURE 800 psi.

Stand-off 80 feet

166 killed

Comparison of Stand-off

Murrah Federal Building Khobar Towers

19 killed

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-26

Vulnerability Radii

FEMA 426, Figure 4-7: Blast Analysis of Building for Typical Large TruckBomb Detonated in Buildings Parking Log, p. 4-12

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-27

Iso-Damage Contours

Stand-off required toprevent lethal glassinjury

Stand-off required toprevent lethal walldamage

Stand-off required toprevent collapse

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-28

Cost Versus Stand-off

FEMA 426, Figure 4-8: Relationship of Cost to Stand-off Distance,p. 4-13

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-29

Blast Load Predictions

Incident and reflected pressure and impulse

Software

Computational Fluid Dynamics

ATBLAST (GSA)CONWEP (US Army)

Tables and charts of predetermined values

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-30

Pressure

versusDistance

FEMA 426, Figure 4-10: Incident Overpressure Measured in Pounds PerSq. Inch, as a Function of Stand-Off Distance and Net Explosive

Weight, p. 4-17

250

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-31

Blast Damage Estimates

Assumptions - pressure and material

Software - SDOF

AT Planner (U.S. Army)

BEEM (TSWG)BlastFX (FAA)

Software - FEM

Tables and charts of predetermined values

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-33

Manchester Bombing

http://e-l155_unit07_manchester.mpg/

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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-34

Summary

Explosive blast physicsBlast damage to buildings

Injury to personnel

Prediction of loading, damage, and injury

Range-to-effect chart Incident pressure chart

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Unit VII Case Study ActivityExplosives Environment, Stand-off Distance,and the Effects of Blast

Background

Purpose of activity: check on learning about

explosive blast

Requirements

Refer to Case Study and FEMA 426

Answer worksheet questions