Unit VI Explosive Blast Unit Objectives Explain the basic physics involved during an explosive blast event, whether by terrorism or technological accident. Explain building damage and personnel injury resulting from the blast effects upon a building. Perform an initial prediction of blast loading and effects based upon incident pressure. Unit VI: Explosive Blast Units I-V discussed Assessments - Risk Units VI and VII explain Blast and CBR Weapons and effects Units VIII and IX demonstrate techniques for site layout and building design to counter or mitigate manmade threats Blast Loading Factors . Ą Type . Ą Energy output (TNT equivalency) . Ą Quantity Figure 4-3: Typical Impulse Waveform, page 4-4 BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-5 Figure 4-2: Reflected Pressure Coefficient vs. Angle of Incidence, page 4-3 BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-6 Incident and Reflected Pressure Blast energy lost at rate of volume increase in X, Y, and Z Figure 4-3: Typical Impulse Waveform, page 4-4 Location of explosive relative to structure . _ Stand-off distance ._ Reflections and reflection angle . Ą Ground . Ą Buildings . _ Identify worst case Blast Compared to Natural Hazards Higher incident pressures and relatively low impulse . Ą High explosive (C-4) . Ą Low-order explosive (ANFO) Ą Aircraft or vehicle crash combines kinetic energy (velocity, mass), explosive loads, and fuel/fire . Ą 200 mph hurricane generates only 0.8 psi, but with very large impulse BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-10 Blast Compared to Natural Hazards Direc t airbl ast caus es more local ized dam age . Ą Component breakage . Ą Penetration and shear . Ą BuildingŐs other side farther away . Ą Reflections can increase damage on any side Greater mass historic ally used for blast protecti on Ą Greater mass usually detrimental during earthquake due to resonance Factors Contributing to Building Damage First approximations based upon: . Ą Quantity of explosive . Ą Stand-off distance between building and explosive . Ą Assumptions about building characteristics Types of Building Damage Direct Air Blast . _ Component failure . _ Additional damage after breaching Collapse . _ Localized . _ Progressive Figure 4-4: Blast Pressure Effects on a Structure, page 4-7 Figure 4-4: Blast Pressure Effects on a Structure, page 4-7 Causes of Blast Injuries (1) Overpressure . _ Eardrum rupture . _ Lung collapse/failure Blast Wave _ Blunt trauma, lacerations, and impalement Fragmentation Bomb or vehicle Street furniture or jersey barriers Building component failure . _ Glass Đ predominant . _ Walls . _ Floors Levels of Protection (1) CONVENTIONAL CONSTRUCTION INCIDENT OVERPRESSURE Levels of Protection (2) CONVENTIONAL CONSTRUCTION INCIDENT OVERPRESSURE YIELD (_TNT Equiv.) 4,000 lb. Reflected PRESSURE 9,600 psi. 15 feet 166 killed YIELD (_TNT Equiv.) 20,000 lb. Reflected PRESSURE 800 psi. Stand-off 80 feet 19 killed BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-25 Iso-Damage Contours Figure 4-8: Relation of Cost to Stand-off Distance, page 4-13 BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-28 Blast Load Predictions Incident and reflected pressure and impulse ._ Software . Ą Computational Fluid Dynamics . Ą ATBLAST (GSA) . Ą CONWEP (US Army) . _ Tables and charts of predetermined values Pressure versus Distance Blast Damage Estimates (1) Assumptions - pressure and material .Ą Software - SDOF . Ą AT Planner (U.S. Army) . Ą BEEM (TSWG) . Ą BlastFX (FAA) . Ą Software - FEM . Ą Tables and charts of predetermined values Blast Damage Estimates (2) (1) "Explosive Shocks in Air" Kinney and Grahm, 1985 (2) "Facility Damage and Personnel Injury from Explosive Blast" Montgomery and Ward, 1993; and "The Effects of Nuclear Weapons, 3rd Edition", Glasstone and Dolan, 1977 Level of Protection Incident Pressure (psi) High 1.2 Medium 1.9 Low 2.3 Very Low 3.5 Below AT Standards > 3.5 Figure 4-5: Explosive Environments Đ Blast Range to Effects, page 4-11, FEMA 426 BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-33 Summary Explosive blast physics Blast damage to buildings Injury to personnel Prediction of loading, damage, and injury . Ą Range-to-effect chart . Ą Incident pressure chart Unit VI Case Study Activity Explosives Environment, Stand-off Distance and the Effects of Blast Background Purpose of activity: check on learning about explosive blast Requirements Refer to FEMA 426 and answer worksheet questions on explosive blast BUILDING DESIGN FOR HOMELAND SECURITY Unit VI-35