Blast Effects & Damage Assessment Flashcards
7 cards from real CES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Blast Effects & Damage Assessment flashcards as text
Which phenomenon explains why a blast in an urban canyon (street lined with tall buildings) can produce higher overpressures at distance compared to an open-field detonation?
Answer: Wave reflection and channeling between building facades amplifying pressure
Urban canyons act as waveguides where repeated reflections between building walls reinforce and channel the blast wave, sustaining higher pressures farther from the source.
What is the significance of the 'specific impulse' in evaluating blast damage to flexible structural components?
Answer: It governs the dynamic load duration relative to the component's natural period
Specific impulse (impulse per unit area) combined with the structural natural period determines whether loading is impulsive, dynamic, or quasi-static, affecting the damage mode.
In a confined explosion (e.g., inside a building), the 'gas pressure loading' phase following the initial blast wave is significant because:
Answer: It sustains elevated pressure for milliseconds to seconds, prolonging structural loading
After the initial dynamic pressure spike, hot combustion gases maintain elevated quasi-static pressure in confined spaces, imposing prolonged loading that can exceed structural capacity.
The Proctor-Redfern index is used in blast damage assessment to evaluate:
Answer: Vibration damage potential to structures from blasting operations
The Proctor-Redfern index correlates peak particle velocity and frequency to structural damage thresholds for buildings affected by blast-induced ground vibration.
Which post-blast indicator is MOST reliable for confirming a high-order detonation (complete initiation) versus a low-order event?
Answer: A well-defined crater with brecciated material and minimal undetonated residue
High-order detonation produces a sharply defined crater, highly fragmented and dispersed material, and virtually no undetonated explosive residue.
Which parameter in the Hopkinson-Cranz scaling law is used to normalize distance when comparing blasts of different charge sizes?
Answer: Distance divided by cube root of charge mass (R/W^(1/3))
The scaled distance Z = R / W^(1/3) normalizes range by the cube root of the TNT-equivalent mass, allowing blast parameters from different charge sizes to be compared on a single curve.
When assessing blast damage to a steel frame structure, permanent lateral drift (sway) beyond what threshold is generally considered indicative of severe structural compromise?
Answer: 2% story height (H/50)
A permanent inter-story drift ratio exceeding approximately 2% (H/50) typically signals significant yielding and potential instability in steel moment-frame structures.