ndt in practise_nvf2013_ramboll finland_guy rapaport
TRANSCRIPT
NON-DESTRUCTIVETESTING IN PRACTICE
Eng. Guy Rapaport
Asset Management, Bridges and Structures
NVF ANNUAL BRIDGE CONFERENCE 2013
BACKGROUND INFORMATIONWHY DO WE NEED NDT ?
• Regular condition evaluation of concrete structures is based mostly on visual inspection according to which we choose locations for a small amount of destructive testing (DT) and sample taking.
Problems:Lack of info what is happing deeper in the concrete str. Pre-stressed structures tendon ducts are left non-evaluatedOpening of the deck surface structures is done quite blindly.What is the depth of cracks?DT and samples target only points of the structure. Do they give a true picture of the investigated structure condition ?
Guy Rapaport
MAIN BENEFITS OF NDT
• Optimizing the sample taking process by pinpointing logical locations for invasive testing
• Enables to evaluate the inside of the concrete structure –to discover what is hidden from the eye.
• Typical disadvantages of NDT:High cost (systems, training process)Useful as “advanced inspection tool for experienced inspectors”. Experienced inspectors are rare and costly.Difficult to use correctly (NOT BLACK BOXES!).
=> Active concrete structures NDT experts in Europe are very scarce, not more than some dozens.
Guy Rapaport
NDT – THE GENERAL PRINCIPLE
• In order to know what is happening inside the concrete we need an “agent” that will penetrate into the object and will return us a message if there is something wrong.
• Suitable “agents” = mechanical waves which we can generate in a controllable manner by an impact or an ultrasonic pulse.
• No further introduction regarding the physics of waves will be given here due to time limit.
Guy Rapaport
SHORT INTRODUCTION : THE MAIN NDT SYSTEMS USUALLY USED
The Ultrasound 3D tomographer system (commercial name: MIRA)
• A state-of-the-art instrument for creating a 3-D representation of internal interfaces (defects, steel…) that may be present in a concrete structure.
• The detection (scanning and interpretation) is done almost in real time (3 sec. delay) and in situ.
• Scanning: only from one side of the object surface. • Effective scanning depth: up to 1 m in heavily reinforced
structures (bridge decks, girders)
Guy Rapaport
The 3D Tomographer System Components:1. Antenna composed of 40 dry point transducers arranged in an
array and a control unit operating the trasducers. 2. Laptop with the MIRA software – responsible for data processing and
graphical presentation (reflected interfaces within the object)3. Antenna power unit with wireless net transmitter.
DPC transducersGuy Rapaport
ANTENNA
ANTENNAPOWER UNIT
Principle
• Based on the ultrasonic echo method using transmitting and receiving transducers in a "Pitch-Catch" configuration, i.e. one row of transducers send out short duration ultrasonic pulses of stress-waves (S- waves) and the other transducers receive the reflected pulses.
Guy RapaportDEFECT BACK WALL
RECEIVING TRANSDUSERSDetection of a defect:
DATA PRESENTATION- THE VISUALIZATION SOFTWARE:
B- SCAN
B- SCAN (ZOOM)
C- SCAN IN DEPTH OF 170 mm
D- SCAN
3D IMAGE
1 st.SCANPOINT
2 nd.SCANPOINT
PLAN VIEW
LASTSCANPOINT
DEPTH
DEPTH
DIRECTION OF SCANNING
CONCRETE SURFACE
Colour scale: more red => the more intensive wave reflections => different material interfaces (such as steel, air…)
C- SCANDUCT
DUCT
SIDE VIEW
ZOOM OF SIDE VIEW
DUCT
LONGITUDINAL VIEW
Guy Rapaport
SHORT INTRODUCTION : THE MAIN NDT SYSTEMS USUALLY USED
The Impact-Echo system (commercial name: DOCter)
• Allows to obtain information on the depth of internal reflecting interfaces (defects) or thickness of a solid member.
• As with the MIRA- tomographer, the detection is done almost in real time, in situ and from one side of the object surface.
• Effective detection depth: up to about 1 m.
Guy Rapaport
The Impact-Echo System Components:1. Mechanical spherical impactor source – generating short
duration pulses2. High fidelity displacement transducer responsible to measure
the surface displacement3. Laptop with the Impact - Echo software data acquisition, data
storage and signal analysis.
Guy Rapaport
IMPACTORS
TRANSDUCER
LAPTOP+SOFTWARE
Principle
• By mechanical impact we generate a short-duration P- wave which penetrates into the test object and is reflected from the back side of a solid object / from a defect inside the object.
• The P-wave undergoes multiple reflections between the object surfaces => recorded by the Impact-Echo system as the “Wave-Form Domain” => mathematically transformed (FFT-algorithm) into the “Frequency Domain” => signal amplitude (“Amplitude Spectrum”).
Guy Rapaport
• In the “Amplitude Spectrum” we look for dominant frequencies (signal peaks) which possibly indicate of reflecting interface (defect / back side).
Guy Rapaport
DATA PRESENTATION OF A TEST POINT:
Wave-Form Domain
Frequency Domain:The Amplitude Spectrum
Dominant peak
Test-points data (dominant frequencies)
The main applications of the Tomographer and the Impact-Echo are:- Locating of casting defects- Internal cracking (delaminations)- Grout injection evaluation in pre-stressed str.
Often used at same the task to back-up each other and to increase credibility of testing results.
Guy Rapaport
SHORT INTRODUCTION OF THE MAIN NDT SYSTEMS USUALLY USED:
The Impulse-Response system (commercial name: s’MASH)
• A different principle than the Tomographer and the Impact-Echo! Measuring the behavior (vibration) of the structure due to an impact not detecting the wave reflections due to an impact.
• The Impulse-Response enables to perform rapid screening of plate-like structures => searching for flaws and identifying suspicious areas for further investigation (Impact-Echo, core drilling…).
• Detection is done almost in real time, in situ and from one side of the object surface.
• Effective testing depth: up to 0,3…0,5 m.
Guy Rapaport
The Impulse-Response System Components:1. A low-strain impactor - hard rubber tipped hammer (~1 kg)
with a built-in load cell capable of measuring dynamic forces 2. Velocity transducer for 360o testing (geophone) that responds
to normal surface motion3. Laptop with the s’MASH software (+Excel®) connected to an
amplifier data acquisition, data storage, signal analysis and graphical presentation
Guy Rapaport
AMPLIFIER
GEOPHONE
LAPTOP+SOFTWARE
RUBBER TIPPED HAMMER
Principle
• With the hammer impact we send a P- wave through the tested object which causes the object to vibrate in a bending mode. The geophone measures the amplitude of the response (the object vibration).
• The data is processed by the computer (FFT- algorithm) to a frequency domain where the amplitude of the signals is presented in Mobility.
• Mobility = velocity (from the geophone) / force (from the hammer).
• The Mobility describes the resistance of a plate-like object to vibrate due to an impact. The higher mobility => the smaller resistance to vibrate
Guy Rapaport
DATA PRESENTATION:
• Processed data is presented in graphics and contour plots
• According the analysis of the frequency domain and other parameters, we can estimate locations of delaminations, debondings, deterioration (F-T, ASR) and casting defects.
• Very useful for mapping the condition of bridge deck surface structures – done from the surface of the asphalt.
Guy Rapaport
Frequency domain
MOBI LI TY
TEST CASES –Usage of the NDT systems in inspection and quality control tasks
TEST CASE 1
AIM: ESTIMATION OF TENDON DUCTS GROUT INJECTION. BRIDGE INSPECTION TASK.
OBJECT: PRESTRESSED CONCRETE BOX-GIRDER BRIDGE. OVERALL LENGTH: 102 m
USED NDT- SYSTEMS:MIRA TOMOGRAPHER AND IMPACT-ECHO
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LOCATION 3 (MID SPAN)
OK(CONFIRMED)
-E UPPER DUCT124 mm => SUSPICIOUS
I-E LOWER DUCTNON-SUSPICIOUS
Guy Rapaport
IMPACT-ECHO
MIRA
TEST CASES –Usage of the NDT systems in inspection and quality control tasks
TEST CASE 2
AIM: ESTIMATION OF TENDON DUCTS GROUT INJECTION.CONSTRUCTION QUALITY CONTROL.
OBJECT: STEEL ARCHED BRIDGE, PRESTRESSED CONCRETE DECK.OVERALL LENGTH: 163 m
USED NDT- SYSTEMS:MIRA TOMOGRAPHER AND IMPACT-ECHOGuy Rapaport
TEST CASES –Usage of the NDT systems in inspection and quality control tasks
TEST CASE 3
AIM: ESTIMATION OF CASTING DEFECTS AND PREVIOUS DEFECTS PATCHING.BRIDGE INSPECTION TASK.
OBJECT: PRESTRESSED CONCRETE GIRDER BRIDGE. OVERALL LENGTH: 59 m
USED NDT- SYSTEMS:IMPULSE-RESPONSE AND IMPACT-ECHO
Guy Rapaport
TEST CASES –Usage of the NDT systems in inspection and quality control tasks
TEST CASE 4
AIM: INTEGRITY ESTIMATION OF CONCRETE SLABS.INSPECTION TASK.
OBJECT: GROUND SUPPORTED AIRPLANES PARKING CONCRETE SLABS.
USED NDT- SYSTEMS:IMPULSE-RESPONSE AND IMPACT-ECHO
Guy Rapaport
PEAK ~220 mm = THICKNESS OF SLAB => OK
PEAK ~165 mm => SUSPICIOUS
Guy Rapaport
LOCATION 2IMPULSE-RESPONSE
IMPACT-ECHO
TEST CASES –Usage of the NDT systems in inspection and quality control tasks
TEST CASE 5
AIM: CONDITION EVALUATION OF BRIDGE DECK SURFACE STRUCTURES (AC SURFACE)BRIDGE INSPECTION TASK.
OBJECT: CONTINUOS CONCRETE SLAB BRIDGE. OVERALL LENGTH: 92 m
USED NDT- SYSTEMS:IMPULSE-RESPONSE AND IMPACT-ECHO
Guy Rapaport
OK - CONFIRMED
LOOSED WATERPROOFING AND CONCRETE DETERIORATION CONFIRMED
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IMPULSE-RESPONSE
TEST CASES –Usage of the NDT systems in inspection and quality control tasks
TEST CASE 6
AIM: INVESTIGATION OF CRACKS - MEASURING THE DEPTH AND WIDTH OF CRACKS BRIDGE INSPECTION TASK.
OBJECT: CONTINUOS CONCRETE GIRDER BRIDGE. OVERALL LENGTH: ~200 m
USED NDT- SYSTEMS:IMPACT-ECHO, SURFER,CRACK WIDTH GAUGE
Guy Rapaport
THANK YOUCONTACT DETAILS:
Guy Rapaport
Senior Consultant , Civil Eng. (Tech. University)Ramboll Finland OyAsset Management, Bridges and Structures
M +358 40 824 [email protected]
www.ramboll.fi
Guy Rapaport