'Deflectograph' (Benkelman beam) testing of roads measures:
Choose the correct answer
Pavement roughness (surface unevenness)
Elastic deflection of pavement surface under standard wheel load — used for overlay design and structural evaluation
Skid resistance (friction coefficient)
Pavement temperature profile
Correct Answer
B. Elastic deflection of pavement surface under standard wheel load — used for overlay design and structural evaluation
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Benkelman beam (IS 10BI-1978) / Falling Weight Deflectometer (FWD): non-destructive pavement evaluation. Benkelman beam: dual wheel load on rear axle (8.2 t standard axle load), probe between tyres measures maximum rebound deflection as vehicle moves forward. Characteristic deflection: 90th percentile value used for overlay design (IRC:81). FWD: impulse load from weight drop — measures deflection basin, back-calculates layer moduli.
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