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Transcript
EMERGING TRENDS IN CIVIL
ENGINEERING
BY : JATIN ARORA,
ANUJ ARORA,
AKSHAY RUHIL
RAHUL CHHOKAR
NDT’S ON
STRUCTURES
NDT-NON DESTRUCTIVE TEST:
Detect Defects , Dimensions etc. without Damaging
Material.
TESTS ON STRUCTRES
NON
DESTRUCTIVE
TEST
DESTRUCTIVE
TEST
NDT Advantages
Access to hidden items – “see through walls”
Better investigations with NDT
Rapid accumulation of data
Generally less expensive than destructive testing
Minimize interruption of building services
Evaluation and quality assurance
NDT Disadvantages
More than one test method may be required
Environmental conditions may effect or
distort results
Construction details & building components may effect
results
Some conditions cannot be determined with
a reasonable degree of accuracy without destructive testing
Typical Conditions to Verify
Verification / identification of member sizes
Location and spacing of embedded items
• Mild reinforcing steel, post-tensioning, conduit
• Masonry ties and hardware
Locating hidden flaws and defects (voids, trapped moisture, poor consolidation, etc.)
Corrosion damage assessment
Concrete properties
Reinforcing steel properties
METHODS FOR NDT ON
STRUCTURES:
IMPACT-ECHO METHOD
SCHMIDT/REBOUND
HAMMER TEST
COVER METER
Impact-Echo Method
It is a technique used for flaw detection in concrete
surface.
Impact-Echo
 Based upon evaluation of stress waves generated by an
elastic impact on a concrete surface
 Originally developed at Cornell University and NIST
by M. Sansalone and N. Carino
P – Compression waves
R - Rayleigh waves
S - Shear waves
Impact-Echo
Propagating P-waves
generated by impact
event. Multiply-reflected
waves are detected by
surface sensor.
Reflected waves set
up a resonance
condition having a
characteristic frequency
Analogous to a bell’s tone
Impact-Echo


Effective in determining
thickness of slabs and depth
of flaws in plate structures
Does not work on beams &
columns
CP
D
2f
  0.96 for plate
IMPACT ECHO
 Applications
 Thickness of members – d,b
 Location of internal defects

Voids / delaminations
 Repair quality assurance
 Internal damage

ASR / DEF / ACR
IMPACT ECHO
• Summary
– Requires significant experience
– Powerful method for flaw detection
– Applications to quality control
– Verification of results is critical
REBOUND HAMMER TEST
OBJECTIVE : Determine the Compressive
Strength of concrete.
WORKING OF SRH
Rebound value V/S Compressive Strength
Advantages & Disadvantages
 Easy to Handle
 Used only on Smooth
 Quick
surfaces
 Moisture Conditions
 Age of Specimen
 Inexpensive
COVER METER TESTING
 OBJECTIVE : Determine Nominal cover.
PRINCIPLE
 Works on Electromagnetic Pulse Induction method
HOW IT WORKS???
ADVANTAGES &
DISADVANTAGES
 High Accuracy
 Limited Detection Range
 Economical
 Spacing depends on Cover
 Not Influenced by Moisture
depth.