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Impulse Response (IR) Applications: Pile integrity testingPile integrity testing Floor slabs, walls and pavementsFloor slabs, walls and pavements Concrete.

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Presentation on theme: "Impulse Response (IR) Applications: Pile integrity testingPile integrity testing Floor slabs, walls and pavementsFloor slabs, walls and pavements Concrete."— Presentation transcript:

1 Impulse Response (IR) Applications: Pile integrity testingPile integrity testing Floor slabs, walls and pavementsFloor slabs, walls and pavements Concrete consolidationConcrete consolidation Cylindrical structures (silos, chimney stacks and tanks)Cylindrical structures (silos, chimney stacks and tanks) Concrete bridgesConcrete bridges Cladding on high-rise buildingsCladding on high-rise buildings

2 Impulse Response Method Impulse Response Method

3 Impulse Response in use on Concrete Tank

4 Impulse Response (IR): Fundamentals in Pile Testing Low strain impact on pile head generates axial bar wave (compression stress)Low strain impact on pile head generates axial bar wave (compression stress) Impact force measured by load cellImpact force measured by load cell Response to impact measured by velocity transducer (geophone) in time domainResponse to impact measured by velocity transducer (geophone) in time domain FFT on force and velocity, combined to give transfer function: Mobility (v/F) v. frequencyFFT on force and velocity, combined to give transfer function: Mobility (v/F) v. frequency Theory well establishedTheory well established

5 Idealized Pile Response Curve

6 Impulse Response (IR): Basics in Structure Testing Low strain impact on structural element generates compression stress wave (as in Impact-Echo method, but lower frequency band [0-800 Hz] & much greater force input)Low strain impact on structural element generates compression stress wave (as in Impact-Echo method, but lower frequency band [0-800 Hz] & much greater force input) Impact force measured by load cellImpact force measured by load cell Response to impact measured by velocity transducer (geophone) in time domainResponse to impact measured by velocity transducer (geophone) in time domain FFT on force and velocity, combined to give transfer function: Mobility (v/F) v. frequencyFFT on force and velocity, combined to give transfer function: Mobility (v/F) v. frequency

7 IR Parameters – Structure Testing Dynamic stiffness in MN/mm from mobility slope between 0-50 HzDynamic stiffness in MN/mm from mobility slope between 0-50 Hz Average mobility from Hz (function of element thickness and concrete quality)Average mobility from Hz (function of element thickness and concrete quality) Slope of average mobility (function of concrete consolidation and proximity of structural shape changes)Slope of average mobility (function of concrete consolidation and proximity of structural shape changes) Peak/average mobility ratio (support beneath slabs on grade, voiding)Peak/average mobility ratio (support beneath slabs on grade, voiding)

8 Stiffness Average Mobility Example of IR Slab Test

9 IR from Highway Pavement Voiding beneath slab

10 IR from Cooling Tower Honeycomb Mobility Slope

11 Test point indicating low thickness and good support (Black) Test point indicating good thickness and good support (Blue) Mobility Plots Impulse Response Test Output

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14 Debonded Bridge Deck Overlay

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