Resilient Modulus Testing and Startup Procedures

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Resilient Modulus Testing and Startup Procedures

• A Product Line

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PRESENTATION OBJECTIVES
What is the Resilient Modulus (Mr) Testing and
Startup Product Line

• Why Mr Testing and the Startup Procedures are
  Important
• Development of the Mr Startup Procedure
• How to Conduct the Mr Startup Procedure
• Who Should Use the Mr Testing and Startup Product
  Line and Why
• How to Get Information on the Mr Testing and
  Startup Product Line

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LTPP Mr Start-up Procedure Product Line

• FHWA LTPP Protocol P46, Resilient Modulus of
  Unbound Granular Base/Subbase Materials and
  Subgrade Soils

FHWA-RD-96-176, Resilient Modulus of
Unbound Materials Laboratory Startup and Quality
Control Procedure

• FHWA Video Tape Series
• Laboratory Resilient Modulus Testing Is This
  the Right Time?
• Laboratory Resilient Modulus Testing Startup and
  Quality Control Procedure
• Laboratory Resilient Modulus Testing Sample
  Preparation and Test Procedure

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Resilient Modulus Lab Tests Videotape 1

• Laboratory Resilient Modulus Testing Is This
  the Right Time?
• 8 minutes
• Explains resilient modulus and what it is used
  for.
• Describes developments that have made the testing
  more consistent and easier to adopt.
• Target Audience Administrators and engineers

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Resilient Modulus Lab Tests Videotape 2

• Laboratory Resilient Modulus Testing Startup
  and Quality Control Procedure
• 15 minutes
• Gives detailed definition of resilient modulus.
• Explains the procedure developed to ensure that a
  lab is set up properly to conduct the test
  procedure and to collect accurate test results.
• Target Audience Laboratory managers and
  technicians

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Resilient Modulus Lab Tests Videotape 3

• Laboratory Resilient Modulus Testing Sample
  Preparation and Test Procedure
• 13 minutes
• Describes each step in the resilient modulus test
  procedure, including how to prepare soil and
  aggregate samples.
• Target Audience Lab managers and technicians

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PRESENTATION OBJECTIVES

• What is the Resilient Modulus (Mr) Testing and
  Startup Procedure Product Line
• Development of the Mr Startup Procedure
• How to Conduct the Mr Startup Procedure
• Who Should Use the Mr Testing and Startup Product
  Line and Why
• How to Get Information on the Mr Testing and
  Startup Product Line

Why Mr Testing and the Startup Procedures Are
Important
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Resilient Modulus 101

• AASHTO Definition
• A measure of the elastic property of soil
  recognizing certain non-linear characteristics.
• Resilient Modulus Mr
• Resilient Modulus elastic modulus (mod. of
  elasticity)
• Resilient Modulus stress/strain
• Resilient Modulus stiffness
• Resilient modulus ? strength

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Typical Elastic Modulus Values (ksi)

• PCC 3,000 6,000
• Asphalt Concrete 500 2,000
• Crushed Stone 20 40
• Silty Soils 5 20
• Clayey Soils 5 10

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Usefulness of Resilient Modulus

• Used to define fundamental material properties
• Used in constitutive models
• Used to predict stress, strain, and displacement
• Used to develop performance models
• Used in current AASHTO pavement design guide
• Used in mechanistic design approach

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The Resilient Modulus Startup Procedure

• Verifies the ability of equipment and personnel
  to perform resilient modulus testing
• Developed by LTPP to ensure consistent,
  repeatable and accurate results
• Implemented in FHWA, state DOTs, academia, and
  industry

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Benefits Of Mr Startup Procedure

• Procedure useful to anyone conducting resilient
  modulus testing
• Prepared for resilient modulus of soils but can
  be applied to asphalt
• Generic procedure useful to anyone performing
  testing using servo-hydraulic test systems (i.e.
  complex modulus, creep, etc.)

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PRESENTATION OBJECTIVES

• What is the Resilient Modulus (Mr) Testing and
  Startup Procedure Product Line
• Why Mr Testing and the Startup Procedures are
  Important
• How to Conduct the Mr Startup Procedure
• Who Should Use the Mr Testing and Startup Product
  Line and Why
• How to Get Information on the Mr Testing and
  Startup Product Line

Development of the Mr Startup Procedure
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Testing and Protocol History

• 1987 - Strategic Highway Research Program (SHRP)
  adopts resilient modulus testing
• 1990 - Initial protocols developed
• 1991 - Resilient Modulus testing began
• 1992 - FHWA assumes leadership of LTPP
• Early 1993 - SHRP Resilient Modulus Testing Ends

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Data Problems 1993/1994 - SHRP data

• Serious flaws found in the data
• Large amount of data deemed unusable
• Probable cause
• faulty electronics
• mechanical problems
• operator error

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Causes of Data Problems

• Sample loading non-symmetrical
• Sample loaded too long
• Deformation occurs prior to loading
• Deformation impulse shorter than load impulse
• Deformation fluctuation
• Deformation flat-line or clipping phenomenon

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High Testing Variability and Low Confidence

• Poor precision and bias
• SHRP precision and bias testing yielded 100
  variation between labs, 50 within lab
• Many practitioners have no confidence in test
  results
• Equipment standardization lacking

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The Mr Testing Challenge

• Significant modulus testing remained to be
  completed
• Need for equipment and operator verification
  procedure established

• Result
• P46 test procedure revised to reflect
• lessons learned
• P46 startup procedure developed to address
• equipment/operator issues

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The Startup Procedure Development Objectives

• Develop a simple, efficient and inexpensive
  methodology to verify equipment performance and
  accuracy of a laboratory
• Verify laboratory ability (personnel/equipment)
  to conduct P46 Resilient Modulus Tests

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PRESENTATION OBJECTIVES

• What is the Resilient Modulus (Mr) Startup
  Procedure Product Line
• Why Mr Testing and the Startup Procedure is
  Important
• Development of the Mr Startup Procedure
• Who Should Use the Mr Startup Procedure and Why
• How to Get Information on the Mr Startup Procedure

How to Conduct the Mr Startup Procedure
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Equipment

• Oscilloscope

• Function Generator

• Strain Indicator

• LVDT Modulator/Oscillator (optional)

• NIST Traceable Proving Rings

• Micrometer Calibrator

• NIST Traceable Pressure Gauge

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The 3-Phase Startup Process

• Verification of Electronic System
• Verification of Mechanical System
• Verification of Laboratory Ability to Conduct P46
  Resilient Modulus Test

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Electronic System VerificationElectrical Method
(Method 1)

• Focuses on the signal path from the transducers
  to the digitized output data
• Input an electrical signal with known frequency
  and amplitude
• Output acquired digitized data
• Compares input and output signals for a range in
  frequency

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Electronic System VerificationMechanical Method
(Method 2)

• Focuses on the signal path from the transducers
  to the digitized output data
• Input a reference LVDT and the machine LVDT
  are exercised mechanically with known frequency
  and amplitude
• Output acquired digitized data and visual
  reference to oscilloscope
• Compares input and output signals for a range in
  frequency
• Note new procedure, not documented in
  FHWA-RD-96-176, simpler than Method 1

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Electronic System VerificationComponents Checked

• Analog signal conditioning
• Digitized signal processing
• Transducers (load cells, LVDTs)
• Signal filters
• Various layers of data acquisition and control
  software

• Acceptance Criteria
• Matched input to output delays lt .5 msec
• Amplitude constant from 2 to 50 hz

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The 3-Phase Startup Process

• Verification of Electronic System
• Verification of Mechanical System
• Verification of Laboratory Ability to Conduct P46
  Resilient Modulus Test

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Mechanical System Verification

• Focuses on the performance capability of the
  laboratory equipment
• Uses NIST traceable calibrated proving rings and
  other measurement devices

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Mechanical System Verification Components

• LVDT Calibration
• Load Cell Zero
• Load Cell Calibration Certificates
• Load Cell Cal. Verification
• Dynamic Response
• Phase Angles
• Triaxial Pressure Chamber