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Dr. ir. Eva Lantsoght 3/31/2015 Sound Applications in Engineering 1
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Dr. ir. Eva Lantsoght
3/31/2015 Sound Applications in Engineering
1
General applications
Applications in bridge engineering
o NDT techniques
o Acoustic emission
o => Proofloading
Summary
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Sound in Engineering? Acoustic
Engineering
o Design, analysis and control of sound
Applications
o Noise control: reduce unwanted noise
o Ultrasound
o Programming digital sound of
synthesizers
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Design of building ~ sound experience
Depends on the use of the building
o Theatre: good speech intelligibility
o Concert hall: quality of sound of music
o Offices: pleasant space, not too noisy
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Noise pollution = disturbances caused by unwanted
sounds
o Transport
o Industry
o Recreation
Civil Engineering
o Development of better material mixes to reduce noise levels of
traffic
o Open graded asphalt
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Used in The Netherlands (ZOAB)
“Whisper asphalt”
Very porous mix
o More coarse material
o Less fine material
Advantages
o Noise reduction: 4dB at 120km/h
o Drainage of water – no aquaplanning
o No rutting
Disadvantages
o Less friction => longer distance when breaking
o Raveling problems
o Shorter lifetime than regular asphalt
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Extending the service life of existing bridges
o Improved calculation methods
o Improved inspection methods
o Improved rehabilitation methods
Inspection:
o Visual inspection
o Non-destructive inspection
o Destructive inspection
o Proofloading
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Non-destructive testing method
Evaluation of material properties (e.g. E-modulus)
For near surface zone
Surface wave dispersion
o Velocity of propagation as function of frequency and wavelength
o In layered system
o To obtain information about layer thickness and E
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More commonly used – with electro-magnetic waves (not
sound waves)
Objects inside depth of concrete
o Reinforcement
o Wire meshes
Produces contour maps of subsurface features
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Fast methods:
o Where sound changes from clear ringing to mute and hollow
Finds delaminations in concrete
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Stress-wave based method
Detection of defects in concrete
o Delamination
Detect wave reflectors
Frequency range 3 - 40 kHz
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Dynamic response characteristics to a given impulse
excitation
Lower range than impact echo
o 0 – 1kHz
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Combine methods to get
overview of condition of
bridge
More info: NDToolbox
o www.ndtoolbox.org
Acoustic waves emitted by material
Caused by irreversible change in internal structure
o Crack formation
o Plastic deformation
Transient elastic waves
< 1kHz – 100MHz
o For applications: 100 kHz – 100 MHz
Event => measurement “hit”
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Use acoustic emission
during proofloading
Information about cracks
before we can see them
Combine with other
measurement techniques
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Levels of assessment of bridges
o Hand calculation
o Linear finite element calculation
o Non-linear finite element calculation
o Probabilistic analysis
o Coupling probabilistic + NLFEA
Still uncertainties?
o Proofloading until different load levels
• No permanent damage
• Unfit for use level
• Repair level
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Extend service life of existing
infrastructure
Effect of deterioration of materials
on structural performance
Test 1 bridge
o But information valid for subset of
bridge stock
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Proofloading to assess capacity of
existing bridge
Study cracks and deformations for
applied loads
Crack formation: acoustic
emissions measurements
Ruytenschildtbrug: testing to failure
Sound in Engineering – many applications
General applications: think about effects of sound for buildings, pavements, ..
Application to bridgeso NDT techniques for better
inspection
o Acoustic emission as measurement technique
o Acoustic emission used in proofloading
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