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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/7/31/2019 E-L155_Unit07 (S)_12-2008
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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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BUILDING DESIGN FOR HOMELAND SECURITY Unit VII-S-35
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
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